Type species.—Nucula hammeri Defrance, 1825b, p. 217.

Remarks.—Palaeonucula was regarded as subgenus of Nuculoma, Nucula, and Nuculopsis (see Hodges, 2000, p. 13) and even as a synonym of the last (Nakazawa & Newell, 1968); it is here regarded as a valid genus, following Carter (1990a) and Hodges (2000).

Stratigraphic range.—Middle Triassic (lower Anisian)—Lower Cretaceous (Aptian) (Komatsu, Chen, & others, 2004; Gang, 2001). The stratigraphic range was here extended, both with respect to the Triassic—Jurassic range in Cox and others (1969), and also to Sepkoski (2002), who assigned a Triassic (Ladinian)—Jurassic (Tithonian) age. The oldest records we accept are Anisian (Tamura & others, 1975; Wen & others, 1976; Komatsu, Chen, & others, 2004). Although Bailey (1978) mentioned the species Palaeonucula strigilata from the Mississippian of Arkansas, this will not be taken into account because the source is an abstract in a conference proceedings volume, and we did not find any reference where the author figured or described the species. The genus was widely mentioned throughout the interval Middle to Late Jurassic (Pugaczewska, 1986; Sha & Fürsich, 1994; Holzapfel, 1998; Harries & Little, 1999; Gahr, 2002; Delvene, 2003; J. Yin & Grant-Mackie, 2005).

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 1).

Tethys domain; Middle Triassic; northern Vietnam (Komatsu, Huyen, & Huu, 2010); Anisian of China (Wen & others, 1976; Komatsu, Chen, & others, 2004), Spain (Márquez-Aliaga, 1985), Malaysia (Tamura & others, 1975); Ladinian of Germany (Ürlichs, 1992), Spain (Márquez-Aliaga, 1985; Niemeyer, 2002), Malaysia (Tamura & others, 1975); Late Triassic; of China (Gou, 1993); Carnian of China (Wen & others, 1976), Italy (Fürsich & Wendt, 1977), Malaysia (Tamura & others, 1975); Norian of China (Lu, 1981), Iran (Repin, 2001; Hautmann, 2001b); Rhaetian of Iran (Hautmann, 2001b), Hungary (Vörös, 1981); Early Jurassic: Hettangian—Sinemurian of England (Liu, 1995; Hodges, 2000); Sinemurian of Turkey (M. A. Conti & Monari, 1991); Sinemurian of southwestern France, Spain, & Portugal (Liu, 1995).

Circumpacific domain; Middle Triassic; Anisian of Chile (Barthel, 1958); Late Triassic; Carnian of Japan (Hayami, 1975); Early Jurassic: Hettangian—Sinemurian of Chile (Aberhan, 1994a; Damborenea, 1996a); Sinemurian of Canada (Aberhan, 1998a).

Boreal domain; Late Triassic; northeastern Siberia (Yakutia Region) (Kurushin, 1987); Triassic—Jurassic; northeastern Asia (Kurushin, 1990).

Paleoautoecology.—B, D, Is, FM; Sb. Holocene nuculids dig into the surface layers of the sediment and remain very close to its surface. They actively use the foot to dig and move around and use the palp proboscis to feed on detritus (Reid, 1998). A similar mode of life is suggested for Palaeonucula. Its external form would facilitate a fairly quick movement through the sediment. Pallial sinus is not observed, and thus it probably did not have siphons. Living nuculids are commonly found in shallow waters and fine-grained sandy sediments, and this is consistent with the associated lithology of fossil species (Hodges, 2000). All previous authors considered Palaeonucula as an infaunal, mobile, and shallow burrowing detritivorous bivalve (see e.g., Pugaczewska, 1986; Damborenea, 1987a; M. A. Conti & Monari, 1991; Holzapfel, 1998; Delvene, 2003).

Mineralogy.—Aragonitic (Carter, 1990a, p. 150). Outer shell layer: aragonite (irregular prismatic). Middle and inner shell layers; aragonite (homogeneous).

Type species.—Trigonucula sakawana Ichikawa, 1949, p. 268.

Stratigraphic range.—Upper Triassic (Carnian—upper Rhaetian) (Hayami, 1975; Hautmann, 2001b). Both Cox and others (1969) and Sepkoski (2002) assigned a Upper Triassic range to this genus. This is here maintained, despite references from the Jurassic and Cretaceous: Trigonucula yunshanensis Yu & Li (in Z. Li & Yu, 1982, p. 94, fig. 13–14) and Trigonucula? yunshanensis (Gu, Li, & Yu, 1997, p. 15, pl. 2,8–9). Nevertheless, both the hinge and shell outline of these species are totally different from those described for Trigonucula sakawana and therefore probably do not belong to the genus (Jingeng Sha, personal communication, 2008). Dickins and McTavish (1963) mention the genus (Trigonucula sp.) in the Lower Triassic (Scythian), but this will not be taken into account for two reasons; (1) it was not included in Cox and others (1969); and (2) the figures in Dickins and McTavish (1963) are impossible to compare due to their poor quality; also the authors pointed out in their discussion (p. 129): “In shape Trigonucula sp. is not unlike Nucula sp. juv. ind. Spath (1930, p. 53, pl. 12,12) from the Lower Triassic (Otoceratan) of Greenland.”

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 1).

Tethys domain; Late Triassic; Norian of Iran (Hautmann, Aghababalou, & Krystyn, 2011); Rhaetian of Iran (Hautmann, 2001b).

Circumpacific domain; Late Triassic; Carnian of Japan (Ichikawa, 1949; Hayami, 1975; Kobayashi & Tamura, 1983b).

Paleoautecology.—B, D, Is, FM; Sb. A relatively quick shallow burrower and detritivorous mode of life is attributed to this genus, similar to the living nuculids (Reid, 1998). Hautmann (2001b, p. 26) described divaricate ornamentation of the shell in his emended diagnosis of the genus. This type of ornamentation has been studied from a functional point of view by several authors (e.g., S. M. Stanley, 1969; Seilacher, 1972), and it is now known that it facilitates excavation (Checa & Jiménez-Jiménez, 2003b).

Mineralogy.—Aragonitic. No specific data about the Trigonucula mineralogy and shell microstructure is known, but a totally aragonitic mineralogy is assumed, according to the diagnosis of subclass Paleaeotaxodonta given by Allen and Hannah (1986).

Type species.—Nucula castor d'Orbigny, 1850, p. 339.

Stratigraphic range.—Upper Triassic (Rhaetian)—Lower Cretaceous (Valanginian) (Laws, 1982; Kaim, 2001). Although Nuculoma was regarded as a typical Jurassic genus (Cox & others, 1969; Sepkoski, 2002), it was found in the Rhaetian of New York Canyon (Laws, 1982; Guex & others, 2003, 2004; Lucas & Tanner, 2004; Lucas & others, 2007) and in the Lower Cretaceous of several localities (Kaim, 2001; Marinov & others, 2006; X. Li, 1990). Accordingly, its stratigraphic range is here extended.

Although originally used for Jurassic forms, several Recent species were also included in Nuculoma. There is no revision of these living species to test which ones are really consistent with the diagnosis, but they will not be taken into account here, because, according to Hansson (1998, p. 93), living species should be included in Ennucula Iredale, 1931 [“Ennucula Iredale, 1931 = Nuculoma: auct., non Cossmann in Cossman & Thièry, 1907 (Nucula castor d'Orbigny, 1850 - Jurassic fossil)”].

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 1). Available information suggests that the genus appeared in the Circumpacific domain, specifically in the Rhaetian of Nevada (Guex & others, 2004), and, during the Early Jurassic, it spread to the Tethys (Hallam, 1972, 1977) and Boreal domains (Zakharov & others, 2006). Later, during the Jurassic, its distribution expanded not only to the European Tethys (X. Li & Grant-Mackie, 1994; Holzapfel, 1998), but also to the Proto-Atlantic (Liu, 1995).

Circumpacific domain; Late Triassic; Rhaetian of Nevada (Hallam & Wignall, 2000); Early Jurassic; Hettangian of Nevada (Hallam & Wignall, 2000).

Tethys domain; Early Jurassic; Sinemurian of Europe (Hallam, 1977).

Paleoautoecology.—B, D, Is, FM; Sb. Fürsich (1982) compared Nuculoma with Recent Nucula, and he assigned it a similar mode of life, moving just below the sediment surface, feeding on the detritus taken with palp proboscis, like other nuculids.

Mineralogy.—Aragonitic (Carter, 1990b, p. 307). Outer shell layer: aragonite (prismatic). Middle and inner shell layers; aragonite (nacreous).

Type species.—Arca rostrata Chemnitz, 1784, pl. 55, fig. 550–551.

Remarks.—Nuculana is a genus especially difficult to identify since the external characters alone, in absence of inner views, are undistinguishable from those of other genera, such as Phaenodesmia Bittner, 1894, Phestia Chernyshev, 1951, Veteranella (Veteranella) Patte, 1926, or V. (Glyptoleda) Fletcher, 1945; hence many Paleozoic and Mesozoic specimens attributed to Nuculana probably belong to other genera (Boyd & Newell, 1979; Damborenea, 1987a; Carter, 1990a; Z. Fang & Cope, 2004).

Leda Schumacher, 1817, is a junior objective synonym of Nuculana (both genera have the same type species). Although this was pointed out by Cox and others (1969), some authors still use the name Leda (e.g., Fürsich & Wendt, 1977; Ruban, 2006a).

Stratigraphic range.—Middle Triassic (Anisian)—Holocene (Tamura & others, 1975). Although there are references for this genus from the Paleozoic, we follow McAlester (in Cox & others, 1969), who considered its range to be from the Triassic to the present (see Nakazawa & Newell, 1968, p. 37–38 for discussion of this genus). Sepkoski (2002) extended it to the lower Induan, but the only mention from the Lower Triassic is Nuculana (Dacryomya) sp. from Japan in Nakazawa (1961); however, this was referred to as Phestia sp. by Nakazawa and Newell (1968). Therefore, the first appearance is regarded as Anisian (Tamura & others, 1975). Furthermore, the record is fairly continuous throughout the entire study interval (see Paleogeographic Distribution, below). However, not all authors agree about the presence of Nuculana in this time interval. Carter (1990a, p. 151) stated that Nuculana did not appear until the Cretaceous. In our opinion, a thorough review of this genus is needed, but it is beyond the scope of this paper, and we will tentatively use the proposed range.

Paleogeographic distribution.—Cosmopolitan (Fig. 2). Although the genus is also present in the Early Jurassic from both the Circumpacific and the Austral domains, these records are Pliensbachian in age (Damborenea, 1987a; Aberhan, 1994a, 1998a).

Tethys domain; Middle Triassic: Anisian of Malaysia (Tamura & others, 1975), northern Vietnam (Komatsu, Huyen, & Huu, 2010); Ladinian of Afghanistan (Farsan, 1975), Spain (Niemeyer, 2002), western Caucasus (Ruban, 2006a); Late Triassic: China (Cowper-Reed, 1927); Carnian of Italy (S. Conti, 1954), Slovenia (Jurkovsek, 1978), China (Wen & others, 1976; Lu, 1981; Gou, 1993; J. Yin, Enay, & Wan, 1999); Norian of Iran (Hautmann, 2001b; Repin, 2001); Norian—Rhaetian of England (Hallam & El Shaarawy, 1982; Hallam, 2002); Rhaetian of Italy (Sirna, 1968), Iran (Hautmann, 2001b; Repin, 2001), Spain (Márquez-Aliaga, Plasencia, & Ros, 2005), China (J. Yin, Enay, & Wan, 1999), Austria (Tomášových, 2006a, 2006b); Early Jurassic: Hettangian of China (J. Yin, Enay, & Wan, 1999); Hettangian—Sinemurian of England (Liu, 1995); Sinemurian of Turkey (M. A. Conti & Monari, 1991).

Circumpacific domain: Late Triassic: Carnian of Mexico (Alencaster de Cserna, 1961), Peru (Jaworski, 1922; Cox, 1949); Norian of Nevada (Laws, 1982).

Boreal domain: Middle Triassic: northern Siberia (Dagys & Kurushin, 1985), Primorie (Kiparisova, 1972); Late Triassic: Carnian of Primorie (Kiparisova, 1972); Triassic-Jurassic: northeastern Asia (Kurushin, 1990). Holocene species have a wide distribution in the boreal domain and in cold-temperate regions.

Austral domain: Late Triassic: Carnian of New Zealand (Marwick, 1953), Carnian—Norian of New Guinea (Skwarko, 1967); Rhaetian of New Zealand (Grant-Mackie, 1960).

Paleoautoecology.—B, D, Is, FM; Sb. Holocene species of this genus are very fast burrowers (Gordillo & Aitken, 2000), moving in the surface of the sediment, with a detritivorous trophic regime (Damborenea, 1987a; M. A. Conti & Monari, 1991; Holzapfel, 1998; Hautmann, 2001b).

Mineralogy.—Aragonitic (Carter, 1990b, p. 311–312, for Recent species). All shell layers: aragonite (homogeneous).

Type species.—Leda inflatiformis Chernyshev, 1939, p. 116.

Remarks.—We regard Polidevcia Chernyshev, 1951, p. 25, as a subgenus of Phestia (see discusion for Polidevcia in Genera not Included, p. 168).

The generic name was first proposed in Chernyshev, 1943, p. 35, but no type species was designated, and it remained a nomen nudem until the type was designated by this author in 1951.

Stratigraphic range.—Middle Ordovician (lower Llanvirn)—Upper Triassic (Carnian) (Carter, 1990a; Z. Fang & Cope, 2004). Cox and others (1969) assigned this genus a Devonian—Lower Triassic range, and Sepkoski (2002), considered it was present from the Devonian (Givetian) to Lower Triassic (data taken from Skelton & Benton, 1993), but the range is extended in this paper. The first occurrence of the genus was Middle Ordovician (Llanvirnian [=overlaps with Darriwilian stage]), according to Z. Fang and Cope (2004), although doubtfully because the figured specimen is an external mold, and the internal features are unknown. Thus, although reference to Phestia seems justified, the same authors note that it externally resembles Glyptoleda (regarded in this paper as a subgenus of Veteranella). Carnian is used here as the upper limit, based on data provided by Carter (1990a, p. 153). This author considered that “Nuculana“‘ sulcellata, from the Italian Carnian, would be better located within Phestia, since its form, ligament structure, and nacreous interior are typical of this genus. Nakazawa and Newell (1968) included Nuculana (Dacryomya) sp., figured by Nakazawa (1961, p. 270, pl. 14,5–7), in Phestia, and thus extended the range of this genus to the Triassic of southwestern Japan. Hautmann and others (2005) mentioned Phestia? cf. perlonga (Mansuy) from the upper Rhaetian of southern Tibet, but this is the type species of Mesoneilo Vu Khuc, 1977a, p. 676, to which the authors did not refer in their paper. This very doubtful record will not be taken into account here.

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 2). Cox and others (1969) regarded Phestia as a cosmopolitan genus, but, although it was very widespread during the Paleozoic, during the studied time interval, it was only present in the Tethys, the Boreal, and the Circumpacific domains.

Tethys domain: late Permian: Iran (Teichert, Kummel, & Sweet, 1973), Tunisia and India (Boyd & Newell, 1979), southern China (L. Li, 1995; Clapham & Bottjer, 2007), Oman (Dickins, 1999); Late Triassic: Carnian of Italy (Carter, 1990a).

Circumpacific domain: late Permian: Japan (Nakazawa & Newell, 1968; Murata & Bando, 1975; Hayami & Kase, 1977); Early Triassic: Japan (Nakazawa & Newell, 1968).

Boreal domain: late Permian: northeastern Russia (Biakov, 1998, 2002, 2006, 2007; Klets & others, 2006).

Paleoautoecology.—B, D, Is, FM; Sb. Phestia most probably had a mode of life similar to the living Nuculana, but it lacked a pallial sinus, so it possibly did not have true siphons (as Nuculana has). Instead, it may have had pseudosiphons created by ciliary connections between the undulations of the mantle (see Bradshaw, 1999, p. 75–76). The genus was regarded as a superficial burrowing detritivore that used the palp proboscis to collect food particles (Hoare, Heaney, & Mapes, 1989; Bradshaw, 1999). R. Zhang and Yan (1993) agreed with this and provided a reconstruction of its mode of life, showing the similarity to Palaeoneilo. The elongated anterior part and the anterior pedal muscle scars, which can be observed in some specimens, suggest it had a large foot that would allow it to burrow effectively (Mángano & others, 1998). These authors associated the ichnofossil Lockeia ornata with Phestia, from which they concluded that Phestia was a vagrant detritivorous capable of moving subhorizontally in the sediment.

Mineralogy.—Aragonitic (Carter, 1990a, p. 154–155). Outer shell layer: aragonite (prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Nuculana (Veteranella) strenua Patte, 1926, p. 158.

Stratigraphic range.—lower Permian (Artinskian)—Upper Triassic (Norian) (Kutassy, 1931; Waterhouse, 1964). The stratigraphic range is here extended with respect to Sepkoski (2002), because we include Glyptoleda and Nucundata as subgenera of Veteranella, according to Cox and others (1969) (see discussion for Glyptoleda and Nucundata in Genera not Included, p. 161, 166).

Cox and others (1969) assigned a Permian—Triassic range to Veteranella; Sepkoski (2002) considered Nucundata to be present in the Permian following Cox and others (1969), Glyptoleda in the late Guadalupian following Waterhouse (1987), and a Norian range for Veteranella following Hallam (1981). J. Chen, Liu, and Lan (1983) mentioned Glyptoleda and other genera attributed to their new subfamily Veteranellinae from Devonian to Permian, but none of these genera was listed as being present before the Carboniferous (Z. Fang & Cope, 2004).

The oldest record of the genus (referred to Nucundata and Glyptoleda) is lower Permian (Artinskian—Kunguarian) of New Zealand (Waterhouse, 1964). The genus was also mentioned from Lower Jurassic age; e.g., Kurushin (1990) quoted Veteranella from the Triassic—Jurassic boundary, confirming its presence in lower Hettangian beds, and Zhakarov and others (2006) mentioned Glyptoleda from the Pliensbachian, but none of them justified the presence of this genus in the Lower Jurassic, because they neither figured the specimens nor included the original source of their data. The youngest record is Upper Triassic: Veteranella (Ledoides) Chen, Wen, & Lan in Wen & others, 1976, from Carnian—Norian of Tibet (Kobayashi & Tamura, 1983a), from Carnian of China (Wen & others, 1976), and from Norian of eastern Tethys (Hallam, 1981).

Paleogeographic distribution.—Tethys (Fig. 2). Veteranella had a wide distribution in Boreal and Austral domains during the early and middle Permian (Waterhouse, 1964, 1983; Biakov, 1998, 2006), but it was not found there during the late Permian.

Tethys domain: late Permian: Changhsingian of Nepal (Waterhouse & Chen, 2006); Late Triassic: China (Kutassy, 1931); Carnian of China (Wen & others, 1976); Carnian and Norian of southern Tibet (Kobayashi & Tamura, 1983a); Norian of Xizang (Tibet) (Z. Fang & others 2009).

Paleoautoecology.—B, D, Is, FM; Sb. Veteranella reidi (Fletcher, 1945) (Permian) is the oldest species with oblique chevron-type ornamentation, which became common among bivalves during the Cenozoic, and is interpreted as an adaptation to rapid escape from potential predators and for minimizing shell damage during burrowing (Checa & Jiménez-Jiménez, 2003a). Numerous studies demonstrated that this type of ornamentation facilitates excavation (S. M. Stanley, 1969, 1970; Seilacher, 1972), so this genus is regarded as a fast burrower.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998). Data provided for subclass Protobranchia. All shell layers: aragonite. Inner shell layer: usually nacreous.

Type species.—Eleganuculana nyeruensis J. Chen & Yang, 1983, p. 356.

Stratigraphic range.—Upper Triassic (Norian) (J. Chen & Yang, 1983). J. Chen and Yang (1983) described Eleganuculana including only the type species from Norian of Knagmar region in Xizang province (southern China). J. Chen, Liu, and Lan (1983) mentioned the same species from the Norian of Tibet.

Paleogeographic distribution.—Eastern Tethys (Fig. 2).

Tethys domain: Late Triassic: Norian of southern China (J. Chen & Yang, 1983), Tibet (J. Chen, Liu, & Lan, 1983).

Paleoautoecology.—B, D, Is, FM; Sb. Similar to Nuculana.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998). No data are available for Eleganuculana. Protobranchia shell mineralogy is fully aragonitic (Carter, Barrera, & Tevesz, 1998).

Type species.—Reticulana elegansa Li & Li in R. Zhang, Wang, & Zhou, 1977, p. 9.

Stratigraphic range.—Upper Triassic. Xiaoshuiculana was described by J. Chen (in J. Chen, Liu, & Lan, 1983) from Upper Triassic of China (Guangdong province), including only the type species. McRoberts (1997a) described a new species: X. tozeri McRoberts, 1997a, from the lower Rhaetian Antimonio Formation of Sonora (Mexico).

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 2).

Tethys domain: Late Triassic: China (J. Chen, Liu, & Lan, 1983). Circumpacific domain: Late Triassic: Rhaetian of Mexico (McRoberts, 1997a).

Paleoautoecology.—B, D, Is, FM; Sb. Xiaoshuiculana is externally similar to Nuculana, but its rostrum is more elongated, and the shell bears oblique ribs (McRoberts, 1997a). These ribs would primarily strengthen the shell and probably also favored efficient excavation (Checa & Jiménez-Jiménez, 2003a).

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998). Data provided for subclass Protobranchia.

Type species.—Phaenodesmia klipsteiniana Bittner, 1894, p. 188.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Rhaetian) (Hallam, 1981; F. Stiller, personal communication, 2008). Cox and others (1969) assigned a Triassic range in Europe to this genus. Sepkoski (2002), allegedly based on data provided by Hallam (1981), assigned it an Anisian—Norian range. However, Hallam (1981) considered that Phaenodesmia Was present in Carnian and Norian (including Rhaetian) deposits. The oldest record is from Anisian beds of the Alps (Diener, 1923) and southwestern China (F. Stiller, personal communication, 2008).

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 3).

Tethys domain; Middle Triassic: Anisian of southwestern China (F. Stiller, personal communication, 2008), southern Alps (Diener, 1923); Late Triassic: Carnian of southern Alps (Diener, 1923).

Circumpacific domain; Late Triassic; South America (Hallam, 1981), Peru (Jaworski, 1922; Körner, 1937); Carnian of Chile (Nielsen, 2005).

Paleoautoecology.—B, D, Is, FM; Sb. We assign to this genus the same mode of life as other nuculids.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998). Data provided for subclass Protobranchia.

Type species.—Nucula lineata Goldfuss, 1837 in 1833–1841, p. 153.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Carnian) (Fürsich & Wendt, 1977; Komatsu, Huyen, & Huu, 2010). Cox and others (1969) considered that Prosoleptus was present in the European Triassic. Sepkoski (2002) assigned it a Middle Triassic(?)—Carnian range following Hallam (1981), who mentioned Prosoleptus from Ladinian and Carnian deposits of western Tethys.

Fürsich and Wendt (1977) found P. lineata (Goldfuss, 1837 in 1833–1841) in the Cassian Formation of the southern Alps. This formation is regarded as upper Ladinian—Carnian in age, and probably for this reason, Hallam (1981) mentioned it from the Ladinian. Although Fürsich (in PBDB, 2005) confirmed that P. lineata occurs only in Carnian beds, it was recently reported from Anisian beds of northern Vietnam (Komatsu, Huyen, & Huu, 2010).

Paleogeographic distribution.—Tethys and ?Boreal (Fig. 3). Prosoleptus was present in the Tethys domain and probably also in northern Siberia (Carnian) (Kurushin, 1984).

Tethys domain; Middle Triassic; Anisian—Ladinian of northern Vietnam (Komatsu, Huyen, & Huu, 2010); Late Triassic; Carnian of Italy (south of the Alps) (Fürsich & Wendt, 1977), Germany (Goldfuss, 1863).

Paleoautoecology.—B, D, Is, FM; Sb. We assign the same mode of life as other nuculids.

Mineralogy.—Aragonitic (Carter, 1990a, p. 159–160; Carter, Lawrence, & Sanders, 1990, p. 315–316). All layers; aragonite (homogeneous).

The original spelling was Palaeaneilo Hall & Whitfield, 1869, p. 6, see McAlester, 1968, p. 41. For the authorship of the paper where this genus was named, see McAlester, 1968, p. 62.

Type species.—Nuculites constricta Conrad, 1842, p. 249.

Remarks.—There is some confusion in the literature among the genera Palaeoneilo, Praesaccella Cox, 1940, and Mesosaccella Chavan, 1947, p. 197 (see discussion in Damborenea, 1987a, p. 54). The problem stems from the fact that there are both Paleozoic and Mesozoic records of this genus and in the presence or absence of resilifer in different species referred to it. Some authors (cf. Damborenea, 1987a, p. 54; Aberhan, 1998a, p. 67) referred Paleozoic species to Palaeoneilo and Mesozoic species to Mesosaccella, but Cox (1937a) stated that there is no reason to separate the Paleozoic and Mesozoic species in different genera; this last criterion is followed here (but see Duff, 1978). Hodges (2000) regarded Palaeoneilo as a morphologically conservative genus that changed very little in general external shape through time.

Stratigraphic range.—Lower Ordovician (Tremadocian)—Lower Jurassic (Toarcian) (Gahr, 2002; Sánchez, 2002). Cox and others (1969) mentioned the range of this genus as Ordovician to the end of the Mesozoic, with a cosmopolitan distribution. Later, Sepkoski (2002) assigned it an Ordovician (upper Arenigian)—Jurassic (?upper Pliensbachian) range, following Pojeta (1971).

The first appearance is from the Lower Ordovician of Argentina (Sánchez, 2002). However, there are some problems with its last appearance. We accept Gahr's youngest record (2002) from the Toarcian; other younger records will not be taken into account, since almost all have some descriptive problems. For instance, Sha and Fürsich (1993) mentioned Palaeoneilo sp. from the Upper Jurassic and Lower Cretaceous of China, but they did not figure or systematically describe it. Later (Sha & Fürsich, 1994; Sha & others, 1998), they studied specimens from the same area and referred them to several species of Nuculana (Praesaccella) and Mesosaccella, but none to Palaeoneilo, although they discussed the problems of differentiating Palaeoneilo and Mesosaccella, and they even gave a series of guidelines to distinguish them. Hu, Jansa, and Wang (2008) also mentioned the genus from the Upper Jurassic—Lower Cretaceous interval, but not only did they not figure it, but they listed it as an ammonoid.

Paleogeographic distribution.—Cosmopolitan (Fig. 3). Palaeoneilo was a cosmopolitan genus during part of Paleozoic and Mesozoic, at least during the study interval considered.

Tethys domain; late Permian; southern China (L. Li, 1995; Y. Wang & others, 2006; Y. Yin & others, 2006; He, Feng, & others, 2007); Early Triassic; China (Z. Yang & Yin, 1979; L. Li, 1995; Sha & Grant-Mackie, 1996); Middle Triassic; Tethys (Hallam, 1981); Muschelkalk and Buntsandstein of Poland (Senkowiczowa, 1985); Anisian of southern China (Komatsu, Chen, & others, 2004); Anisian—Norian of Malaysia and Thailand (Tamura & others, 1975); Ladinian of Afghanistan (Farsan, 1975); Late Triassic; Tethys (Hallam, 1981); Carnian of China (Sha & Grant-Mackie, 1996), southern Alps (Diener, 1923; Kutassy, 1931; Fürsich & Wendt, 1977); Carnian—Norian of China (Wen & others, 1976; Lu & Chen, 1986; Gou, 1993); Norian of southwestern China (Lu, 1981), Singapore (Kobayashi & Tamura, 1968a); Rhaetian of Burma (Diener, 1923); Early Jurassic; Hettangian—Sinemurian of southwestern England (Hodges, 2000); Sinemurian—Pliensbachian of Europe (Hallam, 1987).

Circumpacific domain; late Permian; Japan (Nakazawa & Newell, 1968; Hayami & Kase, 1977); Late Triassic; Mexico, Chile, and Peru (see references in Damborenea, 1987a); Carnian of Mexico (Diener, 1923), Japan (Hayami, 1975); Carnian—Norian of Japan (Onoue & Tanaka, 2005); Early Jurassic; Sinemurian of Chile (Covacevich, Pérez, & Escobar, 1991).

Boreal domain; late Permian; northeastern Russia (Biakov, 1998, 2007); Late Triassic; northeastern Russia (Polubotko & Repin, 1990).

Austral domain; Late Triassic; New Zealand (see references in Damborenea, 1987a), Rhaetian of New Zealand (MacFarlan, 1998) and Argentina (Damborenea & Manceñido, 2012); Early Jurassic; Pliensbachian of New Zealand (MacFarlan, 1998).

Paleoautoecology.—B, D, Is, FM; Sb. Palaeoneilo is regarded as a detritivorous bivalve, a superficial burrower living completely buried, very close to the sediment surface, like some living species of Yoldia (Damborenea, 1987a). It used a palp proboscis to feed on organic particles dispersed in the sediment (Hodges, 2000). Since in some species (e.g., P. elliptica) there is a shallow pallial sinus, presumably it had short siphons. Life position within the substrate most probably was with the posterior end up near the surface of the sediment, as interpreted for Phestia (see R. Zhang & Yan, 1993, p. 854, fig. 2). According to Hodges (2000), shell morphology indicates that Palaeoneilo was a quick burrower, and the foot could help to increase excavation speed.

Mineralogy.—Aragonitic (Carter & Tevesz, 1978; Carter, 1990a, p. 159–161; Carter, Lawrence, & Sanders, 1990, p. 315; Zhu & others, 1990). Outer shell layer: aragonite (homogeneous + fibrous prismatic). Middle and inner shell layers; aragonite (homogeneous).

Type species.—Lapteviella prontchistshevi Kurushin in Dagys & Kurushin, 1985, p. 47.

Stratigraphic range.—Middle Triassic (Anisian) (Dagys & Kurushin, 1985). Lapteviella is a monospecific genus described by Kurushin (in Dagys & Kurushin, 1985) from the Anisian of northern Central Siberia. It is similar to Mesoneilo Vu Khuc, 1977a, but it differs by having a palliai sinus, prosogyrous beaks, and the anterior part of hinge shorter than the posterior. It is also comparable to Palaeoneilo (both have prosogyrous beaks, a similar arrangement of hinge teeth, shallow pallial sinus, concentric ornamentation, adductor muscle scars of similar shape, size, and position) (see fig. 6 and 10 in Dagys & Kurushin, 1985, and fig. 31 in Hodges, 2000). On the other hand, Lapteviella figures in Dagys and Kurushin (1985) show neither an internal septum nor the typical radial groove of Palaeoneilo.

Paleogeographic distribution.—Boreal (Fig. 3).

Boreal domain; Middle Triassic; Anisian of Siberia (Dagys & Kurushin, 1985; Klets, 2006) and northeastern Russia (Konstantinov, Sobolev, & Yadernkin, 2007).

Paleoautoecology.—B, D, Is, FM; Sb. Dagys and Kurushin (1985) indicated the presence of a smooth palliai sinus, from which the presence of short siphons could be inferred. We assign a mode of life similar to other members of the family Malletiidae, i.e., detritivorous, feeding from the substrate surface, and constantly moving to find new food sources.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998), data provided for the subclass Protobranchia.

Type species.—Dianucula sulcata Guo, 1988, p. 113.

Remarks.—Guo (1988) included Dianucula in the family Malletiidae and we follow him, although Z. Fang and others (2009) included it in the family Afghanodesmatidae Scarlato & Starobogatov, 1979.

Stratigraphic range.—Upper Triassic (Norian) (Guo, 1988). Guo (1988) proposed Dianucula from upper Upper Triassic beds, and included two new species, the type and Dianucula ovata Guo, 1988. The genus was recorded from Dapingzhang formation, which is Norian in age (Feng & others, 2005). Sepkoski (2002) did not consider it in his compendium.

Paleogeographic distribution.—Eastern Tethys (Fig. 3). Tethys domain: Late Triassic: Norian of southwestern China (Yunan province) (Guo, 1988).

Paleoautoecology.—B, D, Is, FM; Sb. We assign a mode of life similar to other members of the family Malletiidae, i.e., detritivorous, feeding from the substrate surface, and constantly moving to find new food sources.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998), data provided for subclass Protobranchia.

Type species.—Ningliconcha ningliensis J. Chen & Stiller, 2008, p. 365.

Stratigraphic range.—Upper Triassic (lower Norian) (J. Chen & Stiller, 2008). J. Chen and Stiller (2008) proposed the monospecific genus Ningliconcha and reported it from upper lower Norian of China (Yunnan province).

Paleogeographic distribution.—Eastern Tethys (Fig. 3).

Tethys domain: Late Triassic: Norian of southwestern China (Yunnan province) (J. Chen & Stiller, 2008).

Paleoautoecology.—B, D, Is, FM; Sb. We assign this genus a mode of life similar to the rest of nuculids. The cancellate shell sculpture, characteristic of Ningliconcha (J. Chen & Stiller, 2008), probably aided in burrowing, as it does in other nuculids. The palliai line is integripalliate, and it either did not have siphons or they were short.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998), data provided for subclass Protobranchia.

Type species.—Palaeoneilo cuneata Chen in Ma & others, 1976, p. 195.

Stratigraphic range.—Upper Triassic (middle Norian) (J. Chen & Stiller, 2008). J. Chen and Stiller (2008) proposed Yongshengia based on P. cuneata Chen in Ma & others, 1976 (lower middle Norian of Yunnan) and tentatively included Palaeoneilo mundeni Fleming (in Fleming, Munden, & Suggate, 1954) from the Norian of New Zealand.

Paleogeographic distribution.—Eastern Tethys (Fig. 3).

Tethys domain: Late Triassic: Norian of southwestern China (Yunan province) (Ma & others, 1976; Guo, 1985; Zhu & others, 1990; J. Chen & Stiller, 2008).

Austral domain: Late Triassic: Norian of New Zealand (Fleming, Munden, & Suggate, 1954).

Paleoautoecology.—B, D, Is, FM; Sb. Similar to Palaeoneilo. Yong-shengia is one of the largest nuculanoids and had a large posterior pedal muscle scar (J. Chen & Stiller, 2008). Its large size was probably inconvenient to fast burrowing, but this could be compensated for by a large foot (inferred by the pedal muscle scar).

Mineralogy.—Aragonitic. Zhu and others (1990) studied the shell microstructure of “Palaeoneilo“ cuneata, and they described a probable aragonitic outer shell layer of homogeneous microstructure and aragonitic inner layers.

Type species.—Nucula palmae J. de C. Sowerby, 1824, p. 117.

Remarks.—Cox and others (1969) and other workers (Liu, 1995; Gahr, 2002) considered Rollieria as a subgenus of Nuculana Link, 1807, but here we regard it as a separate genus, following Hodges (2000, p. 36), who remarked that Rollieria lacks some of the characters of Nuculana: “... it does not possess the characteristic elongated posterior, lacks an escutcheon and is suboval in outline.” The name Rollieria also was used for an ammonoid genus, Rollieria Jeannet, 1951, p. 98, but Rollieria Cossman, 1920, has priority.

Stratigraphic range.—Lower Jurassic (Hettangian)—Lower Cretaceous (Hodges, 2000; Jingeng Sha, personal communication, 2008). Cox and others (1969) assigned it a Jurassic range, as did Sepkoski (2002), based on data from Hallam (1977). The oldest record is Hettangian (Hallam, 1972, 1976, 1977, 1987, 1990; Hodges, 2000). Sowerby described the type species from sediments of Carboniferous age, but Hodges (2000, p. 35–36) doubted the presence of Rollieria at that time, based on the fact that the genus was never found again in sediments older than Jurassic.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 4). Tethys domain: Early Jurassic: Hettangian—Sinemurian of southwestern Britain (Hodges, 2000; Mander, Twitchett, & Benton, 2008; Hallam & Wignall, 2000), Europe (Hallam, 1976, 1977, 1987).

Circumpacific domain: Early Jurassic: South America (Damborenea, 2002b).

Paleoautoecology.—B, D, Is, FM; Sb. We assign a mode of life similar to other nuculanoids. General morphology of the species of this genus suggests that it was a quick burrower (Hodges, 2000). Rollieria had a shallow palliai sinus, and thus probably had short siphons. We assume that the Rollieria mode of life was similar to Palaeoneilo.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998), data provided for subclass Protobranchia.

Type species.—Leda renevieri Oppel, 1856 in 1856—1858, p. 215.

Remarks.—Although several authors include Ryderia as a subgenus of Nuculana, it is considered here as an independent genus, following Cox and others (1969). However, we regard Teinonuculana Zhang in Zhang, Wang, & Zhou, 1977, p. 9, as a synonym of Ryderia (see discussion of Teinonuculana in Genera not Included, p. 171).

Stratigraphic range.—Upper Triassic (Rhaetian)—Lower Jurassic (Toarcian) (Liu, 1995; J. Yin & McRoberts, 2006). Cox and others (1969) indicated that this genus was present in Europe during the Jurassic. Sepkoski (2002) restricted its range to the Lower Jurassic (lower Hettangian—upper Pliensbachian), following Hallam (1977, 1987). The oldest record we accept here is Rhaetian, according to Ivimey-Cook and others (1999) and J. Yin and McRoberts (2006). Hodges (2000) considered that the genus was present from Carboniferous to Early Jurassic times, but we did not find any mention older than Rhaetian nor any paper quoting this genus before the Late Triassic. Hodges did not provide references to his statement, and thus it will not be taken into account here. The youngest record is from Toarcian beds (Liu, 1995; Fürsich & others, 2001).

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 4). Tethys domain; Late Triassic; Rhaetian of Tibet (China) (J. Yin & McRoberts, 2006), northeastern England (Ivimey-Cook & others, 1999), southwestern United Kingdom (Mander, Twitchett, & Benton, 2008), southern Germany (Hodges, 2000); Early Jurassic; Germany and China (Hodges, 2000); Hettangian and Sinemurian of Europe (Hallam, 1976, 1977, 1987), eastern Asia and Australasia—Indonesia (Hallam, 1977), southwestern England (Hodges, 2000), southern England (Liu, 1995); Sinemurian of Portugal (Liu, 1995).

Circumpacific domain; Early Jurassic; Canada (Aberhan, 1998a), South America (Hodges, 2000), western Japan (Hodges, 2000).

Paleoautoecology.—B, D, Is, FM; Sb. According to Hodges (2000), Ryderia was a fast burrower. Puri in Cox and others (1969) mentioned a wide and shallow pallial sinus, but Hodges remarked that he did not observe such a feature in any of the specimens he studied, after making a thorough revision of the genus. Moreover, Hodges (2000, p. 45) indicated that “The lack of a pallial sinus and the extremely elongated rostrum suggest that the exposed siphons were short and that the tip of the rostrum lay just below the sediment surface.” Like other nuculanids, it was probably detritivorous.

Mineralogy.—Aragonitic (Carter, Lawrence, & Sanders, 1990, p. 313; Carter, Barrera, & Tevesz, 1998). Outer and middle shell layers; aragonite (?). Middle shell layer: aragonite (?).

Type species.—Nucula lacryma J. de C. Sowerby, 1824, p. 119. Remarks.—Dacryomya is a particularly problematical genus for several reasons. For a long time this genus has been (and still is) regarded as a subgenus of Nuculana. Externally, it is very similar to other nuculanoids, such as Ryderia, Nuculana, or Phestia, and the differences between these genera and Dacryomya are often subjective when internal structures are not seen. For example, the four genera have a rostrate posterior, but in different degree: Ryderia has the longest rostrum, while Dacryomya has the shortest. Hodges (2000, p. 21) pointed out that Dacryomya is very similar to Ryderia and Nuculana and they can be confused, but Dacryomya “is distinguishable from Ryderia by its much greater inflation and shorter rostrum and from Nuculana by its much shorter rostrum and lack of marked ridges bordering the escutcheon.” Moreover, in Cox and others (1969, p. 239), Phestia was described as “Like Nuculana, but with prominent internal ridges,” but Dacryomya and Ryderia also have internal ridges. A thorough review of this genus is needed.

Furthermore, there is no consensus about the family affiliation of this genus: it was referred to Nuculanidae (Cox & others, 1969; Hayami, 1975), Nuculidae (Ivimey-Cook & others, 1999; Hodges, 2000) or Polidevciidae (Carter, 1990a; Delvene, 2000), where we provisionally include it.

Stratigraphic range.—Upper Triassic (Norian)—Upper Jurassic (Kimmeridgian) (Okuneva, 1985; Delvene, 2000). There are some Lower Triassic records of this genus (Nakazawa, 1961; Hayami, 1975), but they will not be taken into account here because Puri in Cox and others (1969) ignored them and assigned it a Middle Jurassic range. Carter (1990a) and Hodges (2000) regarded the first appearance as Lower Jurassic, but Ivimey-Cook and others (1999) reported it from the Rhaetian and Okuneva (1985) from Norian beds. Sepkoski (2002) assigned it a Lower Triassic—Lower Jurassic range, following Hayami (1975), but these data will not be taken into account due to the descriptive issues already mentioned. The youngest age accepted is Upper Jurassic, according to Delvene (2000).

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 4).

Tethys domain: Late Triassic: Rhaetian of England (Ivimey-Cook & others, 1999). Early Jurassic: England (Watson, 1982); Sinemurian of Europe (Hallam, 1976, 1977, 1987), England and Portugal (Liu, 1995), England, Germany, Switzerland, France, and Portugal (Hodges, 2000); Hettangian of China (Hodges, 2000).

Circumpacific domain: Early Jurassic: Japan (Goto, 1983). Boreal domain: Late Triassic: Norian of Transbaykal region (Siberia) (Okuneva, 1985). Early Jurassic: northern Siberia and Arctic region (Zakharov & others, 2006).

Paleoautoecology.—B, D, Is, FM; Sb. Similar to Palaeonucula. Mineralogy.—Aragonitic (Carter, 1990a, p. 153–156). Outer shell layer: aragonite (prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Leda perlonga Mansuy, 1914, p. 82.

Remarks.—Vu Khuc (1977a) included this new genus in the family Ctenodontidae because it possesses a continuous hinge; in other words, the hinge is not interrupted below the umbo. He distinguished Mesoneilo from Phaenodesmia or Palaeoneilo because the first has opisthogyrous beaks and more teeth in the anterior part of the hinge. However, other authors included the type species of Mesoneilo in Nuculana (Gou, 1993; Hautmann, 2001b, p. 30) or in Phestia (Hautmann and others, 2005), but none of them mentioned Mesoneilo. A review of this species is needed to solve this question. Furthermore, some authors suggested that the family Ctenodontidae was exclusively Paleozoic and it is not well defined (Carter, 1990a); all these provide strong arguments to revise the familial affiliation of this genus.

Stratigraphic range.—Upper Triassic (Norian—Rhaetian) (Vu Khuc, 1977a). The genus was reported from Norian of northern Vietnam but a Norian to Rhaetian (Upper Triassic) range was given (Vu Khuc, 1977a). Later Okuneva (1985) referred a specimen from Norian beds of Siberia (Transbaykal region) to Mesoneilo perlonga, but she did not see its hinge and assigned it on the basis of its external shape alone. We think this assignation is very uncertain due to the external similarity with other nuculanoid genera.

Paleogeographic distribution.—Tethys and ?Boreal (Fig. 5).

Tethys domain: Late Triassic: China (Gou, 1993); Norian—Rhaetian of northern Vietnam, Laos, Burma, and southern China (Vu Khuc, 1977a; Vu Khuc & Huyen, 1998), Iran (Hautmann, 2001b).

?Boreal domain: Late Triassic: Norian of Transbaykal region (northern Siberia) (Okuneva, 1985).

Paleoautoecology.—B, D, Is, FM; Sb. Similar to Nuculana.

Mineralogy.—Aragonitic (Carter, Barrera, & Tevesz, 1998). Data about the shell mineralogy of the genus and the family are not available. We assign an aragonitic mineralogy following Carter, Barrera, and Tevesz (1998) for subclass Protobranchia.

Type species.—Pleurodon ovalis Wood, 1840, p. 230.

Stratigraphic range.—Lower Jurassic (Hettangian)—Holocene (Vokes, 1956; McRoberts, Newton, & Allasinaz, 1995). The oldest record of Nucinella is N. liasina (Bistram, 1903) from Hettangian beds of the border between Switzerland and Italy (near lake Lucano) (Vokes, 1956). McRoberts, Newton, and Allasinaz (1995) mentioned the same species from Hettangian beds of the Lombardian basin (Alps). Cox and others (1969), as well as Skelton and Benton (1993) and Sepkoski (2002), agreed with the same time range.

Paleogeographic distribution.—Eastern Tethys (Fig. 5). The genus is now widely distributed geographically (see Cox & others, 1969, p. 269), as it was during older times (e.g., Cretaceous of Georgia [Pojeta, 1988] or Japan [Amano, Jenkins, & Hikida, 2007]). Nevertheless, during the study interval, the genus was only reported from Italy. During the Toarcian, it was also reported from Germany and England (Aberhan, 1993; Harries & Little, 1999).

Tethys domain; Early Jurassic; Hettangian of Italy (Vokes, 1956; McRoberts, Newton, & Allasinaz, 1995).

Paleoautoecology.—B, D-Ch, Is, FM; Sb. Nucinella was a nonsiphonate, active burrower, as indicated by the lack of pallial sinus. It was most probably detritivorous, and it possibly had chemosymbiotic bacteria. According to Allen and Sanders (1969), at least the living species possesses large gills and tiny palps, similar to Solemya, which is not considered as detritivorous (S. M. Stanley, 1970). This suggests that Nucinella may have had a similar feeding habit, but the wide bathymetric range of the living species (between 9 and 900 m, though most live at approximately 400 m) challenges this assumption. The possibility that they have symbiotic relations with chemosynthetic bacteria is strongly supported by the fact that some living species do not even possess palps or intestine (e.g., N. viridula Kuznetzov & Schileyko, 1984, N. maxima (Thiele & Jaeckel, 1931) (Beesley, Ross, & Wells, 1998).

Mineralogy.—Aragonitic (Carter, 1990a, p. 178). Outer shell layer: aragonite (prismatic). Middle and shell layers; aragonite (homogeneous).

Type species.—Solemya mediterranea Lamarck, 1818, p. 488.

Remarks.—Cox and others (1969) regarded Janeia King, 1850, p. 177, as a subgenus of Solemya, but Pojeta (1988, p. 214–215) advised not to use that name since the generic concept lacks meaning. The genus Acharax Dall, 1908a, p. 2, is not included in the study interval, because no records from Triassic or Lower Jurassic deposits were found (see discussion in Genera not Included, p. 156).

Stratigraphic range.—Carboniferous (Upper Pennsylvanian)—Holocene (Pojeta, 1988). Cox and others (1969) assigned Solemya a Devonian—Holocene range, but Pojeta (1988) made an exhaustive revision of Paleozoic solemyoids and concluded that this genus extended from Pennsylvanian to Recent. We follow Pojeta, although other authors (Cope, 1997) extended its range back to the Devonian (Cope did not discuss this matter further), while others considered that the Paleozoic records are doubtful and regard the Jurassic as the first certain appearance (Imhoff & others, 2003; Little & Vrijenhoek, 2003). Ciriacks (1963) mentioned Solemya sp. from upper Permian deposits, but his assignation was only based on external shape. Seilacher (1990) described a new ichnofossil, Solemyatuba, that might be produced by Solemya or other related genera that live in a similar way. This ichnogenus has a wide distribution from Ordovician to Holocene (see Seilacher, 1990, p. 306–309). The only solemyoid genera known during Permian and Triassic times are Solemya and supposedly Acharax, and both have Recent representatives that are able to build Y-shaped tubes (S. M. Stanley, 1970; K. A. Campbell, Nesbitt, & Bourgeois, 2006); therefore, both are good candidates for Solemyatuba builders.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 5). During the time range of this review, Solemya was only reported from the Tethys, whereas it is mentioned from a wider geographic range at other moments of geologic time. Nevertheless, there is certain evidence (ichnogenus Solemyatuba) of its possible presence in Rhaetian beds of Germany and the Permian of Russia (Seilacher, 1990). During the middle Permian, it was reported from Russia and Siberia (Biakov, 2006; Ganelin & Biakov, 2006; Klets & others, 2006) and also from Middle and Late Jurassic from the Tethys (Fürsich, 1982; Komatsu, Saito, & Fürsich, 1993; Sha & Fürsich, 1994) and Austral domains (N. Hudson, 2003). There is a doubtful reference from the Late Triassic of Argentina (Damborenea & Manceñido, 2012).

Tethys domain; late Permian; Changhsingian of China (Teichert, 1990; M. Lin & Yin, 1991); Middle Triassic; Anisian of Hungary (Vörös & Pálfy, 2002); Early Jurassic; Germany (Seilacher, 1990).

Circumpacific domain; late Permian; Wyoming (United States) (Ciriacks, 1963).

Paleoautoecology.—B, Id, S-Ch, FM; Db. Solemya species have elongated and cylindrical shells with which they burrow deep Y-shaped tunnels (S. M. Stanley, 1970). Although their feeding behavior is not fully understood, and many strategies have been proposed: detritivorous (Cope, 1997), filter feeder (S. M. Stanley, 1970; Fürsich, 1982), or the use of both strategies (Liljedahl, 1984), it is clear that most of their food requirements are provided by chemosynthetic symbiotic bacteria (Cavanaugh, 1983). Many Holocene species have very small gut and palp proboscides (Reid, 1998) but have disproportionately large gills where they lodge the chemosymbiotic bacteria (Stewart & Cavanaugh, 2006). They live most of their life inside the Y-shaped tunnels and have a well-developed foot used for burrowing and swimming (Reid, 1998). In addition to the typical Y- or U-shaped galleries (described for Solemya), other types of burrows, such as I- and J-shaped, were attributed to Acharax (Campbell, Nesbitt, & Bourgeois, 2006). Even though they can swim, this is not their main mode of life; and the foot may also be functional to move inside their galleries (S. M. Stanley, 1970). The known species usually live in shallow water areas and are almost always associated with low-oxygen environments rich in sulfur and organic matter (S. M. Stanley, 1970; Pojeta, 1988; Seilacher, 1990). This habitat provides a barrier against oxygen-dependent predators (A. G. Fischer & Bottjer, 1995).

Mineralogy.—Aragonitic (Carter, 1990a, p. 174). Outer shell layer: aragonite (prismatic). Middle and inner shell layers: aragonite (homogeneous).

Type species.—Mytilus modiolus Linnaeus, 1758, p. 706.

Stratigraphic range.—Upper Devonian (Famennian)—Holocene (Cox & others, 1969). Modiolus is a long-ranging genus: having its origin in the Devonian, it is one of the oldest mussel genera with a good living representation (Cox & others, 1969). However, some authors believe that only Cenozoic to Holocene species should be referred to Modiolus (see Hodges, 2000).

Paleogeographic Distribution.—Cosmopolitan.

Paleoautoecology.—B, Se, S, Endo, Sed; By. As suggested by comparison with living Modiolus species, most fossil species are thought to have been semi-infaunal and endobyssate (S. M. Stanley, 1970, 1972). There are many examples of fossil Modiolus found in life position that confirm that they were gregarious and lived semiburied and fixed by their byssus to pebbles and other hard objects buried in the sediment (Fürsich, 1980, 1982). The byssus emerges from the anterior part of the shell. They tend to inhabit intertidal and subtidal, high-energy environments (S. M. Stanley, 1970; Hodges, 2000). Seilacher (1984, p. 228–229), in his own terminology, qualified this genus as a “mud-sticker.”

Mineralogy.—Bimineralic (Hayami, Maeda, & Ruiz-Fuller, 1977; Carter, 1990a, p. 283). Outer shell layer: calcite (prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Promytilus annosus Newell, 1942, p. 38.

Stratigraphic range.—Carboniferous (Mississippian)—Lower Triassic (Induan) (Newell, 1942; Waller & Stanley, 2005). Cox and others (1969) assigned Promytilus a Carboniferous (Mississippian)—Permian range; Sepkoski (2002) assigned it to the Carboniferous (Mississippian)—Permian (upper Guadalupian), following Hayami and Kase (1977). But these last authors mentioned several Promytilus species reported by Nakazawa and Newell (1968) from middle and upper Permian (Changhsingian) of Japan (Tenjinnoki and Gujo formations), although Hayami and Kase (1977, p. 86) only indicate upper Permian (stage unknown). Boyd and Newell (1997) considered Gujo Formation to be of upper Permian age. The presence of Promytilus in Lower Triassic deposits was mentioned by Waller (in Waller & Stanley, 2005) based on P. borealis Kurushin, the original reference is Kurushin (in Dagys & others, 1989). In his original proposal of the genus, Newell (1942) noted that some Triassic and Jurassic specimens attributed to Modiolus could belong to Promytilus instead.

Paleogeographic distribution.—Boreal (Fig. 6). Promytilus had a cosmopolitan distribution during Carboniferous and early Permian times, and lived in the Tethys domain in the late Permian (Wuchiapingian of China: Clapham, & Bottjer, 2007; Malaysia; Nakazawa, 1973), but during the study interval, we only found references from the Boreal domain.

Boreal domain: Early Triassic: Taimyr Peninsula (Russia) (Kurushin in Dagys & others, 1989).

Paleoautoecology.—B, E, S, Epi, Sed; By. According to S. M. Stanley (1972), Promytilus represents an intermediate stage between Mytilus and Modiolus and most probably lived attached by its byssus to hard substrates in the intertidal zone, by analogy with the extant species “Modiolus” pulex (Lamarck, 1819), with which it has a great similarity (see fig. 8 and 9 in S. M. Stanley, 1972). As described by Newell (1942), Promytilus had a well-defined byssal sinus. According to Waller (in Waller & Stanley, 2005), Promytilus is mytiliform in most shell features but possesses an anterior lobe that is smaller and less developed than in Modiolus species.

Mineralogy.—Bimineralic (Newell, 1942; Nakazawa & Newell, 1968). Newell (1942) and Nakazawa and Newell (1968) indicated the presence of a calcitic outer shell layer with prismatic microstructure, but Carter (1990a) doubts that this was the original mineralogy. Outer shell layer: ?calcite (prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Modiolus (Inoperna) carolinensis Conrad in Kerr, 1875, p. 5.

Stratigraphic range.—Upper Triassic (Rhaetian)—Upper Cretaceous (Maastrichtian) (Abdel-Gawad, 1986; Repin, 1996). Cox and others (1969) assigned it a Lower Jurassic (upper Liassic)—Upper Cretaceous range. However, findings referred to the subgenus Triasoperna Repin, 1996, p. 367 [7], indicate that the stratigraphic range of this genus should be extended back to the Upper Triassic (Repin, 1996; Hautmann, 2001b).

Paleogeographic distribution.—Tethys and ?Austral (Fig. 6). Although Inoperna was not widely distributed during our study interval, from Pliensbachian times and throughout all the Jurassic and Cretaceous, it had a cosmopolitan distribution (Freneix, 1965; Vörös, 1971; Hayami, 1975; Wen, 1982; Abdel-Gawad, 1986; Damborenea, 1987a; Liu, 1995; Holzapfel, 1998; Sha & others, 1998; Fürsich & others, 2001; Gahr, 2002; Delvene, 2003; Valls, Comas-Rengifo, & Goy, 2004).

Tethys domain: Late Triassic: Rhaetian of Iran (Repin, 1996; Hautmann, 2001b), northern Caucasus (Repin, 1996), Austria (Tomašových, 2006a, 2006b; Siblík & others, 2010); Early Jurassic: Hettangian of southwestern Great Britain (Hodges, 2000); Sinemurian of Portugal (Liu, 1995).

Austral domain: Early Jurassic: Hettangian—Sinemurian of Argentina (Damborenea, 1996a; Damborenea & Manceñido, 2005b).

Paleoautoecology.—B, Se, S, Endo, Sed; ?Bo. because Inoperna was referred to the subfamily Lithophaginae, several authors suggested the possibility that it was a borer (Damborenea, 1987a; Hodges, 2000; Hautmann, 2001b). However, Pojeta and Palmer (1976) warned that although its morphology is similar to the current Lithophaga, which has a borer mode of life, this particular life habit cannot be certain unless we find the specimens within their holes. In addition, one of those authors found Inoperna plicata J. Sowerby (Middle Jurassic of England) in life position that indicates a semi-infaunal habit. Hodges (2000, p. 64) compared Inoperna with members of the living genus Adula H. Adams & A. Adams, 1857 in 1854—1858, and he suggested that, like them, Inoperna could be a mechanical borer, boring into the substrate with its anterior part and then fixed inside it by the byssus. Most authors regard Inoperna as semi-infaunal endobyssate (Fürsich & others, 1995, 2001; Hautmann, 2001b; Gahr, 2002; Delvene, 2003).

Mineralogy.—Bimineralic (Carter, 1990a, p. 185). There is no information about Inoperna shell mineralogy. We use the data provided for the subfamily Lithophaginae.

Outer shell layer: calcite (homogeneous-prismatic). Middle shell layer: aragonite (nacreous). Inner shell layer: aragonite (nacreousprismatic).

Type species.—Mytilus suprajurensis Cox, 1925, p. 142.

Stratigraphic range.—Upper Triassic (Carnian)—Upper Jurassic (Tithonian) (Kelly, 1984). Cox and others (1969) assigned it a Jurassic range, regardless of previous records that reported the genus from the Upper Triassic of Japan (Kobayashi & Ichikawa, 1950; Nakazawa, 1956; Hayami, 1958a). The latest undoubted record accepted here dates from Tithonian times (Kelly, 1984). Other authors, such as J. D. Taylor, Cleevely, and Morris (1983), mentioned Falcimytilus lanceolatus Sowerby from Lower Cretaceous (Albian), but they neither figured nor described the specimens, they just included them in a list of bivalve shells perforated by gastropods.

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 6). During the study interval, the genus was known from the eastern Tethys, and later in the Jurassic, it was reported also from western Tethys (Hallam, 1976, 1996). The genus is often recorded from this area from Middle and Upper Jurassic beds (Fürsich, 1982; Kelly, 1984; Jaitly, 1988; Liu, 1995, 1999; Holzapfel, 1998; Sha & others, 1998).

Tethys domain: Late Triassic: Carnian—Norian of China (J. Chen, 1982a).

Circumpacific domain: Late Triassic: Carnian of Japan (Kobayashi & Ichikawa, 1950; Nakazawa, 1956; Hayami, 1975); Early Jurassic: Mexico (Damborenea in Damborenea & Gonzalez-León, 1997); Hettangian of Japan (Hayami, 1958a); Hettangian—Sinemurian of ?South America (Damborenea, 1996a).

Boreal domain: Late Triassic: northern Siberia (Dagys & Kurushin, 1985) and eastern Siberia (Kobayashi & Tamura, 1983b); Carnian of Primorie (Kiparisova, 1972); Norian of Russia (Zabaykal region) (Okuneva, 1985).

Paleoautoecology.—B, E, S, Epi, Sed; By. As indicated by its mytiliform outline and its triangular cross section, Falcimytilus probably lived as epibyssate on hard substrates, as living Mytilus species do (Fürsich, 1982; Damborenea, 1987a).

Mineralogy.—Unknown (Carter, 1990a, p. 283; 1990b, p. 400). Outer shell layer: calcite and/or aragonite (?). Middle shell layer: aragonite (nacreous). Inner shell layer: aragonite (nacreous-prismatic).

Type species.—Mytilus lunularis Lycett, 1857, p. 128.

Stratigraphic range.—Lower Jurassic (Sinemurian)—Upper Cretaceous (Maastrichtian) (Cox & others, 1969; Damborenea, 1996a). Cox (1937c) proposed Lycettia and reported it from the Jurassic. Cox and others (1969) considered it was present in the Jurassic and Upper Cretaceous. This discontinuous range is due to the fact that Cuneolus Stephenson, 1941, p. 156, is regarded as a synonym of Lycettia in Cox and others (1969). The type species of Cuneolus (Dreissena tippana Conrad, 1858, p. 328) is typical from Upper Cretaceous beds (Carter, 1990a). Since then, the genus was also reported from Lower Cretaceous deposits (Hayami, 1975; Villamil, Kauffman, & Leanza, 1998; Komatsu & Maeda, 2005).

Paleogeographic distribution.—Austral (Fig. 6). During the earliest Jurassic, Lycettia was only present in the Austral Domain, but during the rest of the Jurassic, it was also reported from the Tethys (Damborenea, 1987a; Liu, 1995; Fürsich & others, 2001; Gahr, 2002).

Austral domain: Early Jurassic: Sinemurian of Argentina (Damborenea, 1996a; Damborenea & Manceñido, 2005b; Damborenea & Lanés, 2007).

Paleoautoecology.—B, E, S, Epi, Sed; By. Lycettia presents some characters that indicate an epibyssate mode of life: external shape triangular in lateral view, the absence of anterior lobe and triangular cross section (S. M. Stanley, 1972). These features are taken to the extreme in this genus, which most probably lived fixed by the byssus to hard substrates in high-energy environments (Damborenea, 1987a). These hard substrates may be other bivalve shells, as Myoconcha from Middle Jurassic (Damborenea, 1987a), or Steinmanella quintucoensis (Weaver) from the Lower Cretaceous (Villamil, Kauffman, & Leanza, 1998).

Mineralogy.—Aragonitic (Carter, 1990b, p. 395–396). Outer shell layer: aragonite (prismatic). Middle shell layer: aragonite (nacreous). Inner shell layer: aragonite (prismatic-nacreous).

Type species.—Mytilus lithophagus Linnaeus, 1758, p. 705.

Stratigraphic range.—Upper Triassic (Norian)—Holocene (Kleemann, 1994). Cox and others (1969) considered the reports of this genus from Carboniferous age to be doubtful, and thus they attributed it a continuous range from Miocene to Recent. These doubtful data are surely from Newell (1942), who pointed out that, although Lithophaga was not very common in the Paleozoic, several species were described from Carboniferous and Permian beds around the world. However, Kleemann (1990) argued that the specimens attributed to Lithophaga from Carboniferous and Triassic age are indeed more than doubtful: they are externally similar to Lithophaga, but they probably did not have an endolithic mode of life. Kleemann (1994) and Carter and Stanley (2004) found specimens of Lithophaga in life position in holes bored inside Upper Triassic corals (as happens in many living species). Since the presence of Lithophaga in pre-Upper Triassic sediments cannot be assured, we will consider that the genus ranges from Upper Triassic to the present. Linck (1972) reported Lithophaga sp. cf. vermiculata Linck from Carnian beds, but he only assigned his specimen to Lithophaga on the basis of its external features, and he did not find it in life position, so we cannot really be sure that it was Lithophaga. Ivimey-Cook and others (1999) found borings that could belong to Lithophaga in Rhaetian deposits from England.

Paleogeographic distribution.—Tethys (Fig. 6). If finding specimens within their borings is a prerequisite to refer them to Lithophaga, then it is very difficult to know what the actual distribution of the genus was. In our study interval, it was reported from Tethys, but at other times (and also Recent), it had a cosmopolitan distribution (Cox & others, 1969).

Tethys domain: Late Triassic: Norian of Germany (Carter & Stanley, 2004); Rhaetian of Austria (Kleemann, 1994; Carter & Stanley, 2004), Iran (Hautmann, 2001b).

Paleoautoecology.—B, Is, S, By, Sed; Bo. Living Lithophaga species are borers in hard substrates, especially in dead and live coral skeletons (Kleemann, 1994; Scott, 1988). They are regarded as chemical borers, because they disaggregate the substrate with the aid of special chemical substances, although it appears that in some species, like Lithophaga nigra (d'Orbigny, 1853), this is supplemented by mechanical boring (L. Fang & Shen, 1988). Regarding fossil species, Lithophaga shells are reported in coral boreholes (Kleemann, 1994; Waller & Stanley, 2005), so the same mode of life is assumed for them. Savazzi (2001) mentioned a possible macrosymbiotic relationship between Lithophaga species burrowing into live corals and the corals themselves, as the coral provides protection and reduces competition with other borers that only bore on nonliving substrates. There is no evidence that the bivalve uses the coral as a food source.

Mineralogy.—Bimineralic (Carter, 1990a, p. 285). Outer shell layer: calcite (homogeneous-prismatic). Middle shell layer: aragonite (nacreous). Inner shell layer: aragonite (nacreous-prismatic).

Although Hautmann (2008) proposed that this family should be included in the superfamily Ambonychioidea, we follow Cox and others (1969), Carter (1990a), Amler (1999), Amler, Fischer, and Rogalla (2000), Waller and Stanley (2005), and Bouchet and Rocroi (2010) to refer it to the Mytiloidea (see discussions in Hautmann, 2001b, 2008; Waller & Stanley, 2005). Some disagreement has arisen in recent years about which genera should be included in this family, and this is summarized below.

Cox (1964) proposed the family and included within it Protopis Kittl, 1904, p. 718 (=Joannina Waagen, 1907, p. 94) and two new genera, Mysidiella Cox, 1964, p. 44 (pro Mysidia Bittner, 1891, p. 113, non Westwood, 1840) and Tommasina Cox, 1964, p. 44 (nom. nov. for Mytiliconcha Tommasi, 1911, non Mytiloconcha Conrad, 1862). Waller (in Waller & Stanley, 2005) proposed the synonymy Protopis (= Tommasina) and advised the exclusion of Protopis and its synonyms (Joannina and Tommasina) from the family Mysidiellidae, but he did not suggest a new allocation. Waller (in Waller & Stanley, 2005) proposed the inclusion of Botulopsis Reis, 1926 (emended by him) and his new genus Promysidiella Waller in Waller & Stanley, 2005. Stiller and Chen (2006), following Cox but without mentioning Waller's paper (in Waller & Stanley, 2005), added to the genera in the family (Protopis, Mytiliconcha, and Mysidiella), their three new genera from the Anisian of China: Leidapoconcha Stiller & Chen, Waijiaoella Stiller & Chen, and Qingyaniola Stiller & Chen. These authors regarded the name Mytiliconcha as valid, and, since Conrad's and Tommasi's names differ in one letter, we agree with Vokes (1980) in regarding Tommasina as an unnecessary name.

On the other hand, Hautmann (2008) proposed the new family Healeyidae, which includes Healeya Hautmann, 2001b, Joannina (which he regarded as valid for substantial differences with Protopis), and, with some hesitation, Protopis and the three genera created by Stiller and Chen (2006): Leidapoconcha, Waijiaoella, and Qingyaniola. In turn, he suggested that Mysidiella, Promysidiella, and Botulopsis should remain in Mysidiellidae, following Waller (in Waller & Stanley, 2005), but including this family within the Ambonychiodea. Hautmann (2008) based these conclusions on the study of the microstructure of one of his specimens of Mysidiella imago Hautmann, 2001b, where he found that the outer shell layer was subdivided into several sublayers (from outside to inside); prismatic, foliar, and coarsely prismatic. He argued that the foliar sublayer and the size of the prisms of the outer sublayer support an origin from myalinids rather than from mytilids. Nevertheless, although no microstructure studies are known for Promysidiella cordillerana (Newton), Newton (in Newton & others, 1987, fig. 13, p. 16) proposed that “abraded specimens exhibit an inner, very fine radial structure, representing silica replacement of primary fibrous prismatic microstructure, homologous to that occurring in outer ostracum of modern Mytilus, as well as Permian mytiloids (Newell, 1942).”

Waller (in Waller & Stanley, 2005) differentiated Mysidiellidae from Myalinidae, because they had different microstructure in the outer shell layers (fibrous prismatic and columnar prismatic, respectively) and different types of ligament (opisthodetic and duplivincular, respectively). But he did not study the microstructural shell details under the electronic microscope, and based his assumption on; “it superficially appears very similar to the microstructure of the outer shell layer of many modern mytilids” (Waller in Waller & Stanley, 2005, p. 8). Hautmann's (2008) proposal seems more solidly supported because it is based on microstructural studies and also on the revision of holotypes and several collections but, in our view, a lot of work is still needed to clarify this question. It is evident that the problems of this family are far from settled, and we therefore include all related genera in this family without further systematic discussions.

We follow Waller and Stanley (2005) and Stiller and Chen (2006) in the allocation of their genera into Mysidiellidae, and we also maintain the inclusion of Protopis and its synonyms. Meanwhile, in the absence of new studies, we believe it is still risky to accept the new family proposed by Hautmann (2008) with its original generic composition. We regard Joannina as a valid genus, following Hautmann (2008).

nom. nov. pro Mysidia Bittner, 1891, non Westwood, 1840, p. 83

Type species.—Mysidia orientalis Bittner, 1891, p. 113.

Stratigraphic range.—Upper Triassic (Carnian—Rhaetian). Cox and others (1969) assigned this genus a Ladinian—Rhaetian range, as did also Sepkoski (2002) and Stiller and Chen (2006). The Ladinian record surely refers to Mysidia taramellii De Toni, 1913, because it is the only one from that stage (data from Diener, 1923); but Waller (in Waller & Stanley, 2005), in his revision of family Mysidiellidae and based on the illustrations provided by De Toni, assigned this species to Botulopsis Reis, 1926, p. 124. Moreover, they also considered that Mysidiella cordillerana Newton in Newton and others, 1987, p. 16, and Mysidiella americana (Körner, 1937) should belong to Promysidiella Waller in Waller & Stanley, 2005, p. 10. They renamed the specimens described by Newton (in Newton & others, 1987) as Krumbeckiella sp. cf. timorensis (Krumbeck, 1924) as their new species Mysidiella newtonae Waller & Stanley, 2005. Szente and Vörös in Budai and others (2003) reported ?Mysidiella sp. from Anisian beds, but this will not be taken into account because the material was not figured.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 7).

Tethys domain: Late Triassic: Carnian of Greece (Diener, 1923), China (Wen & others, 1976); Norian of Turkey (Diener, 1923), China (Kobayashi & Tamura, 1983a); Norian—Rhaetian of Iran (Hautmann, 2001b).

Circumpacific domain: Late Triassic: Carnian of British Columbia (Waller & Stanley, 2005), of Japan (Nakazawa, 1994); Norian of Oregon, United States (Wallowa Terrane) (Waller & Stanley, 2005).

Paleoautoecology.—B, E, S, Epi, Sed; By. The deep byssal notch (see diagnosis in Waller & Stanley, 2005) present in species attributed to this genus indicates an epibyssate mode of life. Their external morphology is similar to mytilid shells, and thus they probably lived in high-energy environments (Newton in Newton & others, 1987). The anterior part of the valves is flat, suggesting the animal lived orthothetically rested, i.e., with the commissure at a nearly right angle to the substrate surface (Hautmann, 2001b, 2008).

Mineralogy.—Bimineralic (Hautmann, 2008). According to Hautmann (2001b), the outer shell layer consists of foliated calcite, but Waller (in Waller & Stanley, 2005) did not find evidence of this type of microstructure in their specimens referred to Mysidiella species. Hautmann (2008), following a suggestion by Waller (in Waller & Stanley, 2005), studied the microstructure in tangential section (rather than in radial section, as he had done previously: Hautmann, 2001b) and found that the outer shell layer of Mysidiella imago Hautmann, 2001b, had several sublayers with prismatic, foliar, and coarsely prismatic microstructure (from outer to inner sublayers). Outer shell layer: calcite (prismatic). Middle and inner shell layers: aragonite (?).

Type species.—Botulopsis reisi Waller in Waller & Stanley, 2005, p. 13 [=Botulopsis cassiana Reis, 1926, non Botulopsis cassiana (Bittner, 1895)].

Remarks.—We include Botulopsis in Mysidiellidae following Waller (in Waller & Stanley, 2005).

Stratigraphic range.—Middle Triassic (Ladinian)—Upper Triassic (Carnian) (Waller & Stanley, 2005). Cox and others (1969) assigned this genus an Upper Triassic range; Sepkoski (2002) considered Botulopsis present in Lanidian and Carnian times, based on data provided by Hallam (1981). Waller (in Waller & Stanley, 2005) emended the generic diagnosis and renamed the type species Botulopsis cassiana Reis, 1926, as Botulopsis reisi Waller in Waller & Stanley, 2005, present in Ladinian beds. Furthermore, Waller (in Waller & Stanley, 2005) included other two species within the genus: Botula? cassiana Bittner, 1895 (Carnian) and Mysidia taramellii De Toni, 1913 (Ladinian). Hautmann (2008) pointed out that Botulopsis was reported from Rhaetian deposits of Germany, and if that reference is correct, the range for this genus should be extended. Stiller (2001) mentioned Botulopsis cassiana from the Anisian of China, but this assignation is wrong (Stiller, personal comnunication, 2008).

Paleogeographic distribution.—western Tethys (Fig. 7).

Tethys domain: Middle Triassic: Ladinian of Austria (Kutassy, 1931), Italy (Reis, 1926; Waller & Stanley, 2005); Late Triassic: Carnian of the Alps (Bittner, 1895; Diener, 1923; Waller & Stanley, 2005).

Paleoautoecology.—B, E, S, Epi, Sed; By. Botulopsis was probably an epibyssate bivalve, on account of its external shell shape, which is quite inflated, and its shallow byssal gape, but possibly it did not inhabit high-energy environments, as Mysidiella did.

Mineralogy.—Bimineralic (Waller & Stanley, 2005). Botulopsis shell microstructure is not known; data used here are taken from the diagnosis of the family Mysidiellidae in Waller and Stanley (2005). Outer shell layer: calcite (fibrous prismatic). Middle and inner shell layers: aragonite (?).

Type species.—Mysidiella cordillerana Newton in Newton & others, 1987, p. 16.

Stratigraphic range.—Middle Triassic (lower Anisian)—Upper Triassic (lower Norian) (Waller in Waller & Stanley, 2005; Newton in Newton & others, 1987). The type species comes from lower Norian beds, but Waller (in Waller & Stanley, 2005) included also the following species: Mysidia americana Körner, 1937, Mytilus eduliformis Schlotheim, 1820, Mytilus otiosus McLearn, 1947, and two new species: Promysidiella planirecta Waller in Waller & Stanley, 2005, and P. desatoyensis Waller in Waller & Stanley, 2005. Waller (in Waller & Stanley, 2005) also pointed out that some species attributed to Mytilus Linnaeus, 1758, from the European Muschelkalk could be included in Promysidiella. In the same paper (Waller in Waller & Stanley, 2005, p. 10), he assigned it a Lower Triassic (Spathian)—Upper Triassic (Norian) range, but this is probably an error, because in the discussion he said, “… the oldest known Promysidiella, P. eduliformis (Schlotheim, 1820) from the lower Middle Triassic.” Hautmann (2008) stated that eduliformis did not appear until early Anisian. There is, however, a Lower Triassic record of this species, although its systematic affiliation needs confirmation: Z. Yang & Yin (1979) mentioned Mytilus eduliformis from the upper Scythian Shihchienfeng Group of Shaanxi province (northern China), and Hautmann and others (2011) mentioned Promysidiella? sp. from southern China.

Paleogeographic distribution.—Tethys, Circumpacific, and ?Boreal (Fig. 7).

Tethys domain: Middle Triassic: Anisian—Ladinian of Spain (Mallada, 1880; Schmidt, 1935; Virgilli, 1958; Márquez-Aliaga, 1983, 1985; Budurov & others, 1991), Italy (Posenato, 2002; Posenato & others, 2002), Germany (Urlichs, 1992), Jordan (Hautmann, 2008); Late Triassic: China (Gou, 1993), Germany (Warth, 1990).

Circumpacific domain: Middle Triassic: Ladinian of Nevada (United States) (Waller & Stanley, 2005); Late Triassic: Carnian of Peru (Körner, 1937), British Columbia (Canada) (Waller & Stanley, 2005); early Norian of Oregon (United States) (Newton, 1986; Newton & others, 1987).

?Boreal domain: Middle Triassic: Anisian of northern Siberia (Dagys & Kurushin, 1985), although we should check if this is taxonomically correct.

Paleoautoecology.—B, E, S, Epi, Sed; By. Newton (in Newton & others, 1987) suggested that the type species was epibyssate with a life style similar to Recent mytilids; based on its external shape, she inferred that it probably lived on hard substrates in high-energy open environments. Some species, such as P. desatoyensis, probably lived gregariously as the living Mytilus edulis Linnaeus does, according to taphonomic analysis of several individuals found in proximity to each other (Waller in Waller & Stanley, 2005). Waller (in Waller & Stanley, 2005) also argued that this species could have had a pendent mode of life, because some features (broad and flat anterior part, anterior margin concave, deep byssal invagination, and byssal notch) indicate that it was strongly attached by the byssus. However, he also suggested an epibyssate mode of life on hard substrates, but solitary (i.e., not forming clusters) for another species, P. planirecta.

Mineralogy.—Bimineralic (Newton in Newton & others, 1987, p. 16; Carter, 1990a, p. 286; Waller & Stanley, 2005, p. 10; but see Hautmann, 2008, p. 556). Outer shell layer: calcite (fibrous prismatic). Middle and shell layers: aragonite (?).

Type species.—Opis (Protopis) triptycha Kittl, 1904, p. 718.

Remarks.—We regard Mytiliconcha Tommasi, 1911 (=Tommasina Cox, 1964) as a synonym of Protopis following Waller (in Waller & Stanley, 2005) (see discussion for Tommasina in Genera not Included, p. 171). Waller (in Waller & Stanley, 2005, p. 9) removed Protopis from the Mysidiellidae and this was further discussed by Hautmann (2008, p. 559), who reillustrated the original specimens of the type species and placed Protopis within the Modiomorphoidea (p. 562).

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Carnian) (Waller & Stanley, 2005; Hautmann, 2008). Hautmann (2008) reviewed the genus Protopis and included there only the type species. Some species traditionally placed within this genus were transferred to Joannina by the author (see discussion for Joannina below). Therefore he assigned the genus to the Anisian. However, he did not refer to other species, as Protopis qinghaiensis Wen, from Carnian—Norian of Qinghai (data provided by Stiller & Chen, 2006). These authors suggested that this species might be included in Waijiaoella Stiller & Chen, 2006, based on its overall shape, but they noted a revision was needed. Waller (in Waller & Stanley, 2005) included Tommasina Cox, 1964 (see discussion in Genera not Included, p. 171) as a synonym of Protopis. Tommasina, or more correctly Mytiliconcha Tommasi, 1911, p. 35 (see Vokes, 1980), is also monospecific, including only the type, Mytiliconcha orobica Tommasi, 1911, from Carnian beds (Cox, 1964; Cox & others, 1969; Stiller & Chen, 2006). Waller (in Waller & Stanley, 2005) indicated its presence in Ladinian times, but this is most probably an error, because the only data source is Tommasi, 1911. Skelton and Benton (1993, p. 243) mentioned as first appearance of the family Mysidiellidae Protopis triptycha Kittl, 1904, from Scythian of the Werfen layers in the Austrian Alps, but it is not possible to verify this record because the authors did not indicate the original source.

Paleogeographic distribution.—Tethys (Fig. 7).

Tethys domain: Middle Triassic: Anisian of the Balkans (Hautmann, 2008); Late Triassic; Carnian of the Alps (Italy) (Cox, 1964; Cox & others, 1969; Stiller & Chen, 2006), China (Stiller & Chen, 2006) .

Paleoautoecology.—B, E, S, Epi, Sed; By. We assign this genus an epibyssate mode of life, like most mysidiellids. The species here recognized within Protopis are Opis (Protopis) triptycha Kittl, 1904 (type species of Protopis) and Mytiliconcha orobica Tommasi, 1911 (type species of Tommasina, considered synonym of Protopis). These species lack the typical anterior lobe of Joannina species and show morphological features similar to other Mysidiellidae, so we suggest they had the same mode of life.

Mineralogy.—Bimineralic(?). There are no data about shell mineralogy and microstructure of this genus. Provisionally, we assign it bimineralic mineralogy.

Type species.—Joannina joannae Waagen, 1907, p. 94.

Remarks.—Krumbeck (1924) included Joannina as a synonym of Protopis and Cox (1964) and Cox and others (1969), among others, accepted this situation, which Waagen (1907) already suspected (Hautmann, 2008). However, Hautmann (2008, p. 559–560) revised the holotypes of the type species of Joannina and Protopis, and he found differences that justify the separation of both genera. This author included within Joannina its type species and tentatively Protopis timorensis Krumbeck, 1924, from the Lower Triassic of Timor, Joannina waageni Schnetzer, 1934, and Joannina aberrans Schnetzer, 1934, both from the Anisian of Austria.

Stratigraphic range.—Lower Triassic (?Induan)—Upper Triassic (Carnian) (Krumbeck, 1924; Stiller & Chen, 2006). The oldest record is from the Lower Triassic (Krumbeck, 1924), and the youngest, Protopis joannae, from Carnian beds (Waagen, 1907; Stiller & Chen, 2006). This species was also mentioned by Hautmann (2008) from Ladinian [data provided by Waagen, 1907], and although Kochanová, Mello, and Siblík (1975, pl. 8,5) mentioned Protopis sp. cf. joannae from the Carnian of the Carpathians, the figured material is only a very poorly preserved fragment, not enough to ascertain if it really belongs to this species. Sha, Chen, and Qi (1990) also mentioned Protopis? sp. cf. P. timorensis Krumbeck, but according to Stiller and Chen (2006), this specimen is badly preserved and thus of doubtful relationship.

Paleogeographic distribution.—Tethys (Fig. 7).

Tethys domain; Early Triassic: ?Induan of Timor (Krumbeck, 1924); Middle Triassic: Anisian of Austrian Alps (Hautmann, 2008), China (Komatsu, Chen, & others, 2004), Hungary (Szente & Vörös in Budai & others, 2003); Ladinian of the Alps (Hautmann, 2008); Late Triassic: Carnian of the Alps (Stiller & Chen, 2006).

Paleoautoecology.—B, Se, S, Endo, Sed; By. According to Hautmann (2008, fig. 5), one of the main differences between Joannina and Protopis is that the former has a distinct anterior lobe. Furthermore, he pointed out that Joannina is modioliform, and thus he suggested an endobyssate mode of life, with the byssus emerging “between this anterior shell lobe and the main body of the shell, a faint radial shell fold creates a gape between both valves for the passage of the byssus” (Hautmann, 2008, p. 559, and see his fig. 5.1). Joannina is externally similar to Leidapoconcha, which probably had also an endobyssate mode of life.

Mineralogy.—Bimineralic(?). Joannina shell mineralogy or microstructure has not been studied. Due to the taxonomic problems already discussed, we cannot refer to the predominant mineralogy in the family (see explanation in Mineralogy of Leidapoconcha below). We provisionally assign it bimineralic mineralogy.

Type species.—Leidapoconcha gigantea Stiller & Chen, 2006, p. 216.

Stratigraphic range.—Middle Triassic (Anisian) (Stiller & Chen, 2006). Leidapoconcha has only been reported from sediments dated as lower upper Anisian (Stiller & Chen, 2006). It is a monotypic genus.

Paleogeographic distribution.—Eastern Tethys (Fig. 7).

Tethys domain: Middle Triassic: Anisian of southwestern China (Guizhou) (Stiller & Chen, 2006).

Paleoautoecology.—B, Se, S, Endo, Sed; By. According to the environment suggested for the deposits where Leidapoconcha, Waijiaoella, and Qingyaniola were found, they lived in fully marine, shallow water, and low-energy settings (Stiller & Chen, 2006). The authors also suggested an endobyssate or epibyssate mode of life for these genera, on the basis of their external morphology, since all of them have byssal gapes. Nevertheless, we think that a semi-infaunal, endobyssate, and sedentary mode of life is more feasible, similar to that proposed for Healeya by Hautmann (2001b).

Mineralogy.—Bimineralic(?). No data about the shell mineralogy and microstructure of this genus are available. Both Waller (in Waller & Stanley, 2005) and Hautmann (2008) agree that the family Mysidiellidae probably had a bimineralic shell, with calcitic outer shell layer and ar agonitic middle and inner layers, but they disagree about the outer shell layer microstructure. However, Hautmann (2008) included Leidapoconcha, Waijiaoella, and Qingyaniola in his new family Healeyidae. No microstructural studies have been done on its type genus (Healeya), but an original aragonitic mineralogy is suggested by the fact that the shell is often found completely recrystallized (Hautmann, 2008). Stiller and Chen (2006) indicated the presence of recrystallized calcite in the shell of the specimens they studied.

Type species.—Waijiaoella elegans Stiller & Chen, 2006, p. 219.

Stratigraphic range.—Middle Triassic (Anisian) (Stiller & Chen, 2006). Waijiaoella was only reported from sediments dated as lower upper Anisian (Stiller & Chen, 2006). The genus includes two species, the type and Waijiaoella speciosa Stiller & Chen, 2006.

Paleogeographic distribution.—Eastern Tethys (Fig. 7). See Leidapoconcha (p. 26).

Paleoautoecology.—B, Se, S, Endo, Se. See Leidapoconcha (p. 26).

Mineralogy.—Bimineralic(?). See Leidapoconcha (p. 26).

Type species.—Qingyaniola mirabilis Stiller & Chen, 2006, p. 223.

Stratigraphic range.—Middle Triassic (Anisian) (Stiller & Chen, 2006). See Leidapoconcha (p. 26).

Paleogeographic distribution.—Eastern Tethys (Fig. 7). See Leidapoconcha (p. 26).

Paleoautoecology.—B, Se, S, Endo, Se. See Leidapoconcha (p. 26).

Mineralogy.—?Bimineralic. See Leidapoconcha (p. 26).

Newell in Cox and others (1969, p. 256) pointed out that the phylogeny of this group is not well known, and several decades later, the problems to distinguish their genera still persist, although many authors have recently discussed this topic (see e.g., Damborenea, 1987a; Amler, 1989; Carter, 1990a; Stiller, 2006). The trouble is mainly focused on Parallelodon Meek & Worthen, 1866, Grammatodon Meek & Hayden, 1860, and Cosmetodon Branson, 1942. The general shell shape, the teeth (especially their arrangement), and ornamentation are features that were commonly used as criteria to distinguish these taxa (Manceñido, González, & Damborenea, 1976). Although it seems that the orientation of hinge teeth is a good criterion, it is not enough, since, as has been shown, in some Parallelodon species, the teeth may change their orientation during ontogeny (Newton in Newton & others, 1987; Hautmann, 2001b). In this regard, Stiller (2006, p. 12) concluded that “the convergence direction of the long posterior pseudolaterals appears to be taxonomically more reliable than the direction of the short anterior cardinals; the anterior ends of the posterior teeth intersect the dorsal shell margin in the Parallelodontinae and the ventral margin of the hinge plate in the Grammatodontinae.” The difficulty of applying these criteria is that hinge teeth are not observed in most specimens. A thorough review of this family is needed, but it is beyond the scope of this paper.

Type species.—Macrodontella lamellosa Assmann, 1916, p. 616.

Remarks.—Although Assmann (1916) included Macrodontella in the family Arcidae, we follow Newell in Cox and others (1969) and later authors (e.g., Sha, Chen, & Qi, 1990) and refer it to the Parallelodontidae.

Stratigraphic range.—Middle Triassic (Anisian). Assmann (1916) described this monotypic genus from lower Muschelkalk (probably Anisian) from the Erzführender Dolomit Formation in Silesia (Poland). Cox and others (1969) assigned it a Middle Triassic range. Macrodontella was reported from middle Anisian beds from Poland (Malinowskiej, 1979). The genus was also doubtfully recorded from Chinese Anisian deposits (Sha, Chen, & Qi, 1990).

Paleogeographic distribution.—Tethys (Fig. 8).

Tethys domain: Middle Triassic: Poland (Assmann, 1916; Cox & others, 1969), Anisian of Poland (Malinowskiej, 1979), China (?Qinghai province) (Sha, Chen, & Qi, 1990).

Paleoautoecology.—B, E-Se, S, Epi-Endo, Sed; By. Sha, Chen, and Qi (1990) suggested an epibyssate and suspensivorous mode of life; however, Aberhan and others (2004) assigned it a semi-infaunal mode of life. Because it is a monotypic genus with reduced distribution, it is difficult to obtain good illustrations to help settle this question.

Mineralogy.—Aragonitic (Carter, 1990a, p. 189). No data about shell mineralogy-microstructure of Macrodontella are available. Data provided for the family Parallelodontidae (Carter, 1990a).

Type species.—Gramatodon (Catella) laticlava Healey, 1908, p. 13.

Stratigraphic range.—Upper Triassic (Carnian)—Lower Paleogene (Danian) (Wen & others, 1976; Heinberg, 1999). Healey (1908) described Catella as a subgenus of Grammatodon from the Rhaetian of Burma. Cox and others (1969) assigned it an Upper Triassic—Jurassic range, and Sepkoski (2002) assigned a Triassic (Norian)—Paleocene (Thanetian) range, and presumably got his data from Heinberg (1978), but in this last paper, the figure with the ranges of genera seems to indicate Danian, not Thanetian. The youngest record is Paleocene (Danian) (Heinberg, 1999), because we were not able to corroborate the range offered by Sepkoski (2002). The oldest record considered for almost all authors for Catella is Norian (Wen & others, 1976; Hallam, 1981; J. Zhang, 1983; Hautmann, 2001b). Nevertheless, Guo (1988) proposed a new subgenus, Catella (Oceanopieris), from the Carnian of Yunnan (China), which was considered a junior synomym of Catella by Z. Fang and others (2009). Catella shows a seemingly discontinuous distribution through time. Although it was widely mentioned from the Upper Triassic (see next section), it is not reported again until the Upper Jurassic (X. Li, 1990; Monari, 1994) and later in the Upper Cretaceous (Heinberg, 1999).

Paleogeographic ditribution.—Eastern Tethys (Fig. 8).

Tethys domain: Late Triassic: Carnian of Yunnan (China) (Guo, 1988); Norian of Yunnan (China) (J. Zhang, 1983), Himalaya (southern Tibet) (Wen & others, 1976; J. Yin & Enay, 2000; Hautmann, 2001b); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Burma (Healey, 1908), Indochina (Kutassy, 1931).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Several aspects of the shell shape, such as the reduced anterior part of the shell, absence of ventral flattening, external modioliform appearance, and presence of byssal sinus, suggest that Catella was probably an endobyssate semi-infaunal bivalve (Heinberg, 1999; Hautmann, 2001b).

Mineralogy.—Aragonitic (Carter, 1990a, p. 184–185). There are no data about Catella shell mineralogy or microstructure. Data provided for superfamily Arcoidea.

Type species.—Macrodon rugosus Buckman in Murchison, Buckman, & Strickland, 1844, p. 99.

Stratigraphic range.—Middle Devonian—Upper Cretaceous (Amler & Winkler Prins, 1999). Traditionally, all Paleozoic members of the family Parallelodontidae were referred to Parallelodon (Newell in Cox & others, 1969); however, Manceñido, González, and Damborenea (1976) and Yancey (1985) noticed that many of these species should be referred to Grammatodon (Cosmetodon) instead. The same happens with some Mesozoic species referred to Parallelodon, which would better be allocated in Grammatodon (Grammatodon) (Damborenea, 1987a). Many Paleozoic species were described based on poorly preserved material or with little morphological discussion (Amler, 1989; Anelli, Rocha-Campos, & Simões, 2006). In practice, it is hard to distinguish between Parallelodon and Grammatodon (Boyd & Newell, 1979). For this reason, the range assigned here is provisional for these two genera, awaiting revision of Paleozoic material.

Paleogeographic distribution.—Cosmopolitan.

Paleoautoecology.—B, E, S, Epi, Sed; By. There are endobenthic and epibenthic species within this genus (S. M. Stanley, 1972). Those with a modioliform appearance are presumably endobyssate. Others are quadrangular and morphologically very similar to epifaunal Recent arcids. Some species, such as P. monobensis Nakazawa, 1955, have a large ventral sinus indicating an epibyssate mode of life. Other species, such as P. groeberi Damborenea, 1987a, and P. riccardii Damborenea, 1987a, were also epifaunal and probably attached to hard substrates with a strong byssus, as living Area species do (S. M. Stanley, 1970; Damborenea, 1987a). Parallelodon riccardii might even have been a nestler (Damborenea, 1987a), as suggested by its elongated and laterally compressed shell (Thomas, 1978). However, P. tenuistriatus (Meek & Worthen, 1866) and P. hirsonensis (Archiac, 1843) were probably endobyssate (Quiroz-Barroso & Perrilliat, 1998; Fürsich & others, 2001). They are often found associated with corals and sponges (Damborenea, 1987a; Newton in Newton & others, 1987). But they could also live attached on rocks in open substrates (Newton in Newton & others, 1987). J. Yin and McRoberts (2006) suggested that representatives of the genus had an epibyssate and suspensivorous mode of life. We assign Parallelodon the predominant mode of life of species attributed to this genus.

Mineralogy.—Aragonitic (Carter, 1990a, p. 189–190). Outer shell layer: aragonite (prismatic). Middle shell layer: aragonite (cross-lamellar). Inner shell layer: aragonite (complex cross-lamellar).

Type species.—Arca (Cucullaea) inornata Meek & Hayden, 1859, p. 51.

Remarks.—We regard Cosmetodon Branson, 1942, p. 248, as a subgenus of Grammatodon, following most authors (Fürsich, 1982; Kelly, 1984; Yancey, 1985; Damborenea, 1987a; Gardner & Campbell, 1997; Ivimey-Cook & others, 1999; Hautmann, 2001b; Nakazawa, 2002; Delvene, 2003). Some authors (Tashiro, 1986; Stiller, 2006) argued that Cosmetodon is a separate genus. Two other subgenera are included in our study range: Grammatodon and Indogrammatodon Cox, 1937b.

Stratigraphic range.—lower Permian (Artinskian)—Upper Cretaceous (Maastrichtian) (Yancey, 1985; Carter, 1990a). Newell in Cox and others (1969) included all Paleozoic members of the family Parallelodontidae within Parallelodon, but as stated above, there are certain specimens that should be attributed to Grammatodon instead (Manceñido, González, & Damborenea, 1976; Yancey, 1985). In the absence of a good review of Paleozoic members of this family, the first appearance is from the Permian Pacific margin (Manceñido, González, & Damborenea, 1976; Yancey, 1985) and the last appearance is from Upper Cretaceous age (Carter, 1990a). Sepkoski (2002) assigned it a Jurassic (Hettangian)—Cretaceous (?Cenomanian) range, following Cox and others (1969) and Hallam (1977).

Paleogeographic distribution.—Cosmopolitan (Fig. 8).

Tethys domain; late Permian: Malaysia (Nakazawa, 2002), Greece (Clapham & Bottjer, 2007); Middle Triassic: Anisian of Malaysia (Tamura & others, 1975); Late Triassic; Carnian of Malaysia (Tamura & others, 1975); Norian of Iran (Repin, 2001); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Burma (Healey, 1908), northeastern England (Penarth Group) (Ivimey-Cook & others, 1999), Tibet (Hautmann & others, 2005), Austria (Tomašových, 2006a); Early Jurassic: Tibet (Gou, 2003); Hettangian of Tibet (Hautmann & others, 2005); Sinemurian of Vietnam (Hayami, 1964; Sato & Westermann, 1991), Portugal and southern England (Liu, 1995), China (Stiller, 2006).

Circumpacific domain: Early Jurassic: western United States (Oregon) (Fraser, Bottjer, & Fischer, 2004); Hettangian of Japan (Hayami, 1958d); Hettangian—Sinemurian of Japan (Hayami, 1975); Sinemurian of Chile (Aberhan, 1994a) and Canada (Aberhan, 1998a).

Austral domain: Middle Triassic: Ladinian of New Zealand (Marwick, 1953); Early Jurassic: Argentina (Damborenea, 1987a; Damborenea & Lanés, 2007); Hettangian—Sinemurian of Neuquén Basin (Damborenea & Manceñido, 2005b).

Boreal domain: late Permian: Norway (Nakazawa, 1999); Early Jurassic: Hettangian of Greenland (Liu, 1995).

Paleoautoecology.—B, E, S, Epi, Sed; By. The assignation of one specific mode of life to this genus is difficult. Duff (1978) and Damborenea (1987a) found several inconsistencies, depending on which features of the shell were observed. According to authors and species, Grammatodon was interpreted as epibyssate (Fürsich, 1982; Fürsich & others, 2001; Hautmann, 2001b; Delvene, 2003; J. Yin & Grant-Mackie, 2005; Aberhan, Kiessling & Fürsich, 2006; Stiller, 2006; Tomašových, 2006a), semi-infaunal (Fürsich, 1982; Pugaczewska, 1986; Delvene, 2003) or infaunal (Duff, 1978; Damborenea, 1987a; Gardner & Campbell, 1997; Harries & Little, 1999). According to S. M. Stanley (1972), the members of the subfamily Grammatodontinae would be rather epibyssate as suggested by their elongated shell by comparison with living species. However, in the same genus, we find species (such as G. toyorensis Hayami, 1959) with dorsally inflated shells and no evidence of byssal gape, which could be interpreted as shallow burrowers (Damborenea, 1987a); others [such as G. (Cosmetodon) mediodepressum (Krumbeck, 1913)] with an elongated ventral margin, which were probably epibyssate (Hautmann, 2001b), and finally, others [such as G. (Cosmetodon) keyserlingii (d'Orbigny, 1850) or G. (C.) marshallensis (Winchell, 1862)] showing a modioliform shape with an expanded posterior part, which are interpreted as semi-infaunal (S. M. Stanley, 1972; Fürsich, 1982). Having said that, we assign the prevailing inferred mode of life, i.e., epibyssate, to the genus.

Mineralogy.—Aragonitic (Carter, 1990b, p. 326). Outer shell layer: aragonite (cross-lamellar). Middle shell layer: aragonite (?). Inner shell layer: aragonite (cross-lamellar).

Type species.—Bapristodia serrata Guo, 1988, p. 116.

Stratigraphic range.—Upper Triassic (Norian) (Guo, 1988). Guo (1988) proposed Bapristodia, a monospecific genus, from the Maichuqing formation dated as Norian (H. Yao & others, 2007).

Paleogeographic distribution.—Eastern Tethys (Fig. 8).

Tethys domain: Late Triassic: Norian of southwestern China (Yunan) (Guo, 1988).

Paleoautoecology.—B, E, S, Epi, Sed; By. We assign it the most common mode of life in the family Parallelodontidae. The external morphology of B. serrata is similar to some epibyssate species of Grammatodon, although no evidence of byssal gape is mentioned in the diagnosis offered by Guo (1988) [translated English version in Z. Fang & others, 2009].

Mineralogy.—Aragonitic (Carter, 1990a, p. 184–185). There are no data about the shell mineralogy or microstructure of Bapristodia. Data provided for superfamily Arcoidea (Carter, 1990a).

Type species.—Cucullaea auriculifera Lamarck, 1801, p. 116.

Remarks.—One of the subgenera of Cucullaea lived during the study interval: Idonearca Conrad, 1862, p. 289 (type species, Cucullaea tippana Conrad, 1858, p. 328).

Stratigraphic range.—Lower Jurassic (Hettangian)—Holocene (Hayami, 1958d; Beesley, Ross, & Wells, 1998). Cucullaea had its origin during the Early Jurassic and reached its greatest diversity during the Late Cretaceous, followed by a gradual decline until the present. Although Cox and others (1969) assigned it a discontinuous range [Jurassic (Liassic)—Cretaceous, Holocene], Cucullaea was present during the Cenozoic (Griffin, 1991; Griffin & Nielsen, 2008). The oldest record is from the Hettangian (Hayami, 1958d, 1975). It is currently represented by a single species, C. labiata (Lightfoot, 1786), with an Indo-Pacific distribution (Beesley, Ross, & Wells, 1998).

Paleogeographic distribution.—Circumpacific (Fig. 9). Although during other times this genus was widely distributed, during the Early Jurassic (Hettangian and Sinemurian), it was only found in northwestern Pacific. During the Pliensbachian and Toarcian, it was distributed in the Arctic region (Zakharov & others, 2006), South America (A. F. Leanza, 1940, 1942; Damborenea, 1987a; Aberhan, 1994a), and Europe (Fürsich & others, 2001; Gahr, 2002).

Circumpacific domain: Early Jurassic; Hettangian of Japan (Hayami, 1958d, 1975).

Paleoautoecology.—B, Is-Se, S, SM; Sb. The species referred to Cucullaea have a very inflated quadrangular shell, with a truncated posterior end, indicative of a slow shallow-burrowing mode of life, as in modern species of Anadara (S. M. Stanley, 1970). The only extant species, C. labiata, lives at depths down to 200 m, buried in sand, with the anterior part downward (Beesley, Ross, & Wells, 1998). Damborenea (1987a) noted that shells of C. jaworskii A. F. Leanza and C. rothi A. F. Leanza (Lower Jurassic) lack epizoan organisms, whereas other epifaunal invertebrates from the same beds bear abundant epifauna. Thus we regard Cucullaea as a shallow infaunal or even semi-infaunal bivalve (see Damborenea, 1987a, p. 75).

Mineralogy.—Aragonitic (Carter, 1990b, p. 326). Outer shell layer: aragonite (prismatic or cross-lamellar). Middle shell layer: aragonite (cross-lamellar). Inner shell layer: aragonite (complex cross-lamellar).

Type species.—Eophilobryoidella sinoanisica Stiller & Chen, 2004, p. 414.

Stratigraphic range.—Middle Triassic (upper Anisian) (Stiller & Chen, 2004). Eophilobryoidella is particularly abundant in the middle part of the Leidapo Member of Qingyan formation. Up to now, the family Philobryidae was believed to range from the Eocene to the present time, but this finding extends its stratigraphic range back to the Middle Triassic. Therefore, the idea that this family evolved from the family Limopsidae, which has a Cretaceous origin, is invalidated (Stiller & Chen, 2004; Oliver & Holmes, 2006).

Paleogeographic distribution.—Eastern Tethys (Fig. 9).

Tethys domain: Middle Triassic: late Anisian of southwestern China (Guizhou province) (Stiller & Chen, 2004).

Paleoautoecology.—B, E, S, Epi, Sed; By. Living members of family Philobryidae are suspensivorous and live at depths that can exceed 1000 m, almost always attached (epibyssate) to other organisms (Beesley, Ross, & Wells, 1998). Stiller and Chen (2004) interpreted that Eophilobryoidella had a similar mode of life, although a byssal notch is not observed. These authors suggested that species of this genus were epibyssate, because they found epizoan organisms attached to the shells while the bivalve was alive. According to the environment in which these organisms lived, they concluded the species of Eophilobryoidella preferred shallow, low energy and normal salinity waters.

Mineralogy.—Aragonitic (Carter, 1990a, p. 195; Carter, 1990b, p. 328). There is no information about Eophilobryoidella shell mineralogy or microstructure. Data from Recent Philobryidae specimens are used. Outer shell layer: aragonite (?). Middle shell layer: aragonite (cross-lamellar). Inner shell layer: aragonite (complex cross-lamellar).

Type species.—Lucina duplicata Münster, 1841, in Goldfuss, 1833–1841, p. 227.

Stratigraphic range.—Upper Triassic (Carnian). There are some Hoferia records from the Ladinian (Hallam, 1981; Kobayashi & Tamura, 1983a; Sepkoski, 2002), but none of these figure or indicate the original source of the data, and all of them are referred to the Alps. Hoferia was listed from the Cassian Formation in the southern Alps; according to Fürsich and Wendt (1977, fig. 2), this unit is upper Anisian to the lower part of the upper Carnian in age. Nevertheless, Fürsich (in PBDB, 2005) provided data from this paper, and he clearly assigned a Carnian age to Hoferia specimens. In addition, Kobayashi and Tamura (1983a) also mentioned Hoferia from the Norian of Yunnan, but they did not provide any bibliographic reference. The only quotation of this genus from Yunnan is Cowper-Reed (1927), but from the Carnian. The last author only had a badly preserved internal mold of a right valve, and he included the specimen in Hoferia, because it shows a characteristic anterior lobe. We assign here a Carnian range to Hoferia.

Paleogeographic distribution.—Tethys (Fig. 10).

Tethys domain: Late Triassic: Carnian of the Italian Alps (Leonardi, 1943; Fürsich & Wendt, 1977), Yunnan (China) (Cowper-Reed, 1927).

Paleoautoecology.—B, Is, S, Endo, SM; Sb. The family Pichleriidae includes members of both shallow burrowers and those with epibyssate attached. Hoferia presents a byssal groove (see diagnosis in Cox & others, 1969, p. 265), and thus it must have been byssate. The globose shell suggests it was an endobyssate shallow burrower that lived near the surface or even semi-infaunally.

Mineralogy.—Aragonitic (Carter, 1990a, p. 196). There are no specific data for Hoferia, but we provisionally use those provided by Carter (1990a) for the family Pichleriidae, provided by the analysis of Pichleria, a genus closely related to Hoferia (see above).

Type species.—Cucullaea auingeri Laube, 1865, p. 62.

Stratigraphic range.—Upper Triassic (Carnian) (Cox & others, 1969). Cox and others (1969) assigned Pichleria to the Upper Triassic, and Sepkoski (2002) to the Triassic (upper Ladinian—Carnian), following Hallam (1981) (see discussion for Hoferia). Wen and others (1976) mentioned Pichleria from the Norian of China, but the figured specimens (pl. 7,6–13) are members of family Limidae.

Paleogeographic distribution.—Tethys (Fig. 10).

Tethys domain: Late Triassic: Carnian of southern Alps (Italy) (Bittner, 1894, 1895; Diener, 1923; Leonardi, 1943; Corazzari & Lucchi-Garavello, 1980), southern Tunisia (Desio, Rossi Ronchetti, & Vigano, 1960).

Paleoautoecology.—B, Is-Se, S, Sed; ?. The shell morphology indicates that Pichleria probably lived semi-infaunally or infaunally near the substrate surface. Byssal notch and sinus appear to be absent.

Mineralogy.—Aragonitic (Carter, 1990a, p. 196). Outer shell layer: aragonite (prismatic). Middle shell layer: aragonite (nacreous). Inner shell layer: aragonite (prismatic).

Type species.—Arcoptera elegantula Bittner, 1895, p. 126.

Remarks.—Cox and others (1969) regarded Elegantarca (nom. nov. pro Arcoptera Bittner, 1895, p. 126, non Heilprin, 1887, p. 98) as a synonym of Hoferia, but Stiller (personal communication, 2005) argued to maintain them as separate genera, due to differences in orientation, number, and shape of the hinge teeth and other morphological disparities. In his own words: “Elegantarca shows some distinct morphological differences to Hoferia. Outer shell shape: Elegantarca has a large posterodorsal wing separated from the body of shell by a distinct but generally blunt posterior umbonal ridge (this diagonal ridge is lacking in Hoferia); Elegantarca in many cases is distinctly produced posteroventrally, Hoferia generally is shorter and more rounded. However, more important are differences in the hinge structure: Hoferia has a hinge with at least 10 short, taxodont teeth, which are radially arranged in two groups (Bittner, 1895; Broili, 1904; Cox & others, 1969); Elegantarca has very few, strong, radial teeth below the umbo, and one anterior and one posterior elongated tooth (about parallel to the hinge margin) (Broili 1904). The Chinese Elegantarca subareata Chen, Ma, & Zhang, 1974 has a hinge like the bivalves figured by Broili (1904, Arcoptera).”

Vokes (1980) regarded Bittnerella Dall, 1898, p. 613 (nom. nov. pro Arcoptera Bittner, 1895) as a valid name with priority over Elegantarca, but Bittnerella was included in the synonymy of Hoferia by Cox and others (1969), and now the name Bittnerella Dagys, 1974, p. 77, is used for a brachiopod genus.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Carnian) (Bittner, 1895; Komatsu, Chen, & others, 2004). The oldest known record of Elegantarca dates from Anisian times (Komatsu, Chen, & others, 2004; Stiller, personal communication, 2005) and the youngest from the Carnian (Bittner, 1895).

Paleogeographic distribution.—Tethys (Fig. 10).

Tethys domain: Middle Triassic: Anisian of southern China (Anonymous, 1974; Komatsu, Chen, & others, 2004; Stiller, personal communication, 2005), Bosnia (Diener, 1923); Ladinian of southern Alps (Italy) (Diener, 1923); Late Triassic: Carnian of southern Alps (Italy) (Bittner, 1895; Broili, 1904; Waagen, 1907).

Paleoautoecology.—B, Se, S, Endo, Sed; By. See Hoferia. Komatsu, Chen, and others (2004) regarded it as endobyssate semi-infaunal.

Mineralogy.—Aragonitic (Carter, 1990a, p. 196). See Hoferia.

Type species.—Myalina goldfussiana de Koninck, 1842 in 1841– 1844, p. 126.

Stratigraphic range.—Carboniferous (lower Mississippian)—upper Permian, ?Lower Triassic (McRoberts, personal communication, 2005). Both Cox and others (1969) and Sepkoski (2002) assigned a Carboniferous (Lower Mississippian)—upper Permian range to this genus, but previously and subsequently, several authors mentioned Myalina from the Lower Triassic (e.g., Kiparisova, 1938; Newell & Kummel, 1942; Ciriacks, 1963; Dagys & Kurushin, 1985; Schubert, 1993; Schubert & Bottjer, 1995; McRoberts & Newell, 2005). All these references are better regarded as belonging to Promyalina, Myalinella, or even Promytilus (McRoberts, personal communication, 2005; McRoberts, 2005). So we leave the Triassic record of this genus as doubtful pending a good review of the problem. According to McRoberts (personal communication, 2005), no myalinid reached the Middle Triassic, since the only genus mentioned for that age (Aviculomyalina) should in fact be included in the Pteriidae or Malleidae.

Paleogeographic distribution.—Circumpacific (Fig. 11). Myalina had a cosmopolitan distribution, but from the late Permian, we only find records from the Tethys and Circumpacific domains. The family Myalinidae had significant diversity and abundance during the Carboniferous and Permian, but at the Permian—Triassic extinction, this family was decimated, later to disappear by the end of the Early Triassic (McRoberts, 2005). The doubtful Early Triassic records belong to the Circumpacific and Boreal domains.

Circumpacific domain: late Permian: western United States (Newell, 1942; Walter, 1953; McRoberts & Newell, 2005), Japan (Nakazawa & Newell, 1968; Hayami & Kase, 1977).

Paleoautoecology.—B, E, S, Epi, Sed; By. Species attributed to this genus have different morphologies and, consequently, their mode of life can be semi-infaunal (endobyssate) to epifaunal (epibyssate) (S. M. Stanley, 1972, fig. 12). Upper Permian specimens have reduced anterior lobes and, in some cases, bear a byssal sinus (M. lamellosa McRoberts & Newell, 2005; M. plicata McRoberts & Newell, 2005; M. copei Whitfield, 1902; see diagnosis in McRoberts & Newell, 2005), characters that indicate a byssate mode of life. Nevertheless, their thick and heavy shells were probably not functional for byssus attachment, and they were not active (Newell, 1942). According to McRoberts and Newell (2005), M. lamellosa probably lived lying on its anterior side, with an almost vertical commissure, lightly resting on its left valve. The species had a gregarious mode of life and is found in groups, as are many Recent mussels (Newell, 1942). Substrate type should also be taken into account: in soft substrates, they commonly adopt an endobyssate mode of life to become stable, while on hard substrates, they were frequently epibyssate.

Mineralogy.—Bimineralic (Newell, 1942, p. 33–34; Carter, 1990b, p. 331). Outer shell layer: calcite (prismatic-homogeneous). Inner shell layer: aragonite (nacreous).

Type species.—Myalina meeki Dunbar, 1924, p. 201.

Remarks.—Newell (1942) described Myalinella as a subgenus of Myalina, pointing out the differences between Myalinella and other myalinids, such as Myalina (Myalina). Later, the same author (in Cox & others, 1969), raised Myalinella to genus level.

Stratigraphic range.—Carboniferous (Visean)—Lower Triassic (upper Olenekian) (R. Zhang & Pojeta, 1986; Fraiser & Bottjer, 2007a). Newell in Cox and others (1969) assigned a Carboniferous (Pennsylvanian)—Lower Triassic range to this genus and recorded it from Europe, United States, India, and Greenland. However, R. Zhang and Pojeta (1986) reported the first record of Myalinella from the Visean of China. The youngest record is Olenekian (Newell, 1942; Schubert, 1993; Schubert & Bottjer, 1995; Fraiser & Bottjer, 2007a).

Paleogeographic distribution.—Tethys, Boreal, and Circumpacific (Fig. 11). Myalinella had a wide distribution, but, during the late Permian, it seems restricted to few records; for instance, it was extensively mentioned from the western coast of the United States from the Permian until Guadalupian times (e.g., Newell, 1942; Ciriacks, 1963), but, from then on, it is only recorded from the Lower Triassic (e.g., Schubert, 1993), possibly due to lack of upper Permian deposits in this area. Even though during the early Permian it was present in the Tethys (e.g., Zheng, 1993), it seems to have been absent from this domain during the late Permian. However, it was recently reported from the Lower Triassic (Hautmann & others, 2011). Fraiser and Bottjer (2007a) studied several Lower Triassic sections from Japan and Italy, and they did not report Myalinella, but they did find another genus of the same family (Promyalina).

Tethys domain: Early Triassic: Induan of southern China (Hautmann & others, 2011).

Boreal domain: Early Triassic: Greenland (Newell, 1942).

Circumpacific domain: Early Triassic: United States (Schubert, 1993; Schubert & Bottjer, 1995; Fraiser & Bottjer, 2007a).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Specimens of this genus are usually found with closed valves, suggesting that they lived in low energy areas and/or were buried (Newell, 1942). They tolerated a wide salinity range (Newell, 1942), and they were found in fully marine (Kues, 2004) to estuarine environments (Mack & others, 2003). The shell shows some features indicative of a probable endobyssate and semi-infaunal mode of life: they have an anterior lobe and a byssal sinus, and their shells are small and fragile (Newell, 1942; McRoberts & Newell, 2005).

Mineralogy.—Bimineralic (Newell, 1942, p. 33–34). There are no available data about Myalinella shell microstructure. Newell (1942) indicated that, unlike most myalinids, Myalinella exhibits the same structure in both valves. We assign the type present in members of the family Myalinidae.

Type species.—Promyalina hindi Kittl, 1904, p. 690.

Stratigraphic range.—upper Permian (upper Changhsingian)—Lower Triassic (upper Olenekian) (Fraiser & Bottjer, 2007a; He, Feng, & others, 2007). Cox and others (1969) assigned a Lower Triassic range to this genus, and they also doubtfully considered its presence in upper Permian beds. Although some authors (Sepkoski, 2002; McRoberts, 2005; McRoberts & Newell, 2005) only took into account the Lower Triassic records, others (Farabegoli, Perri, & Posenato, 2007, fig. 7; He, Feng, & others, 2007, fig. 5.18) accepted the late Permian records (late Changhsingian) from the Tethys domain. Promyalina showed a maximum abundance at the beginning of the Early Triassic, and it went extinct at the end of the same epoch.

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 11).

Tethys domain: late Permian: Italy (Farabegoli, Perri, & Posenato, 2007), Changhsingian of southern China (He, Feng, & others, 2007); Early Triassic: China (Z. Yang & Yin, 1979; C. Chen, 1982; F. Wu, 1985; Lu & Chen, 1986; Ling, 1988; Komatsu, Huyen, & Chen, 2006, 2007), northern Vietnam (Komatsu, Huyen, & Chen, 2006, 2007); Induan of Oman (Krystyn & others, 2003; Twitchett & others, 2004), south of China (Hautmann & others, 2011); Induan—early Olenekian of Italy (Broglio-Loriga & others, 1990; Fraiser & Bottjer, 2005a, 2007a; Posenato, 2008a).

Circumpacific domain: Early Triassic: early Olenekian of Japan (Nakazawa, 1961; Hayami, 1975; Fraiser & Bottjer, 2007a); Olenekian of western United States (Ciriacks, 1963; Boyd, Nice, & Newell, 1999; Boyer, Bottjer, & Droser, 2004; Fraiser & Bottjer, 2007a).

Boreal domain: Early Triassic: northern Siberia (Dagys & Kurushin, 1985); Induan of Greenland (Wignall, Morante, & Newton, 1998; Wignall & Twitchett, 2002).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Promyalina was one of the more widely distributed genera during the Early Triassic worldwide. Together with Eumorphotis and Unionites, it dominated the bivalve fauna of the seas at the beginning of the Triassic (Fraiser & Bottjer, 2005b, 2007a). It showed a typical opportunistic behavior, being more abundant when conditions were adverse but disappearing as soon as environmental conditions were restored, probably by competition with more specialized taxa. Morphological characteristics indicate a probable semi-infaunal and endobyssate mode of life, similar to Myalina (Schubert, 1993). Posenato (2008a) suggested an epibyssate mode of life.

Mineralogy.—Bimineralic (McRoberts & Newell, 2005). No data are available for shell mineralogy or microstructure of the species of this genus. We use data for the family Myalinidae (see McRoberts & Newell, 2005). Outer shell layer: calcite (prismatic-homogeneous). Inner shell layer: aragonite (nacreous).

Type species.—Aviculomyalina lata Assmann, 1916, p. 608.

Remarks.—Both McRoberts (2005) and Waller (in Waller & Stanley, 2005) pointed out that Aviculomyalina could be better located within the Pteriidae or Malleidae. We keep it in Myalinidae until this matter is adequately discussed.

Stratigraphic range.—Middle Triassic (Anisian) (Cox & others, 1969). Assmann (1916) described the genus from the Lower Muschelkalk (probably Anisian), in the “Erzführender Dolomit” Formation of Silesia. Other authors also reported it from Anisian beds (Malinowskiej, 1979; Sepkoski, 2002). The range of this genus could be extended to Carnian and Norian if Aviculomyalina? williamsi (McLearn, 1941) were considered to belong to this genus, as proposed by Waller (in Waller & Stanley, 2005), rather than to Mysidioptera as proposed by Newton (in Newton & others, 1987).

Paleogeographic distribution.—Tethys (Fig. 11).

Tethys domain: Middle Triassic: Anisian of Poland (Assmann, 1916; Malinowskiej, 1979), Alps (?Switzerland) (Zorn, 1971).

Paleoautoecology.—B, E, S, Epi, Sed; By. An epibyssate mode of life is suggested by some shell features, such as the external shell morphology, the presence of byssal gape, and the flattened anterior margin (Newton in Newton & others, 1987).

Mineralogy.—Bimineralic. There is no information about Aviculomyalina shell mineralogy or microstructure, but we regard it equivalent to Promyalina.

The family Inoceramidae is especially problematic, due partly to its great morphological variability, and partly to the lack of consensus among specialists about the taxonomically significant characters. It is often difficult to discern between the different genera assigned to this family because, if internal characters are not shown, the external shape is extremely variable, even within species (Crame, 1982). This is the consequence of convergent evolution resulting from functional and ecological constraints, the presence of few easily distinguishable characters, the great variability within species, and also the high evolutionary rates they exhibit. As a result, the group has a rich fossil record with a long history but with the serious drawback of a wide disparity of concepts used by successive specialists (Harries & Crampton, 1998).

ex Voronetz, 1936, p. 23, 34, nom. nud.

Type species.—Parainoceramus bulkuriensis Voronetz, 1936, p. 24, 34.

Remarks.—The generic name Parainoceramus was proposed by Voronetz (1936, p. 23, 34) on the basis of badly preserved specimens from sediments then dated as Carnian from northern Siberia. The author included four species in this new genus, but he did not designate a type, and thus this name was not available. Years later, Cox (1954) completed the requirements for the validity of the name by designating P. bulkurensis Voronetz as the type (ICZN, 1999, Art. 13B, 50). He did not see Voronetz's material, but, nevertheless, he included within Parainoceramus two other species that are widely distributed in the European Jurassic: “Crenatula“ ventricosa J. de C. Sowerby, 1823, and Inoceramus substriatus Münster, 1835, in Goldfuss, 1833–1841. On the basis of his knowledge of these last species, he emended Voronetz's original diagnosis to include an anterior auricle and anterior teeth on some species. Cox's (1954) concept of the genus Parainoceramus was followed by nearly all later authors dealing with Jurassic material (e.g., Hayami, 1960; Speden, 1970; Duff, 1978; Damborenea, 1987b; J. Chen, 1988; M. A. Conti & Monari, 1991; Monari, 1994), who added more Jurassic species from around the world. Nevertheless, it is all too evident that this was reluctantly done in many instances, in the absence of a better alternative. Another point overlooked in the Treatise (Cox & others, 1969, p. 320) and by later authors is that Emel'yantsev and others (1960; see also Muromtseva, 1979; and Astafieva, 1986) had redated the beds where Voronetz's original material was found to be upper Permian (Wuchiapingian and Changhsingian), and thus the stratigraphic range of Parainoceramus sensu Cox (1954) should be upper Permian (Siberia), Hettangian to Tithonian (cosmopolitan), with no record during the Triassic. A breakthrough was provided by Astafieva (1986, 1993), who revised Voronetz's original material and concluded that the type species should be referred to the Paleozoic genus Kolymia Licharew in Licharew & Einor, 1941. Thus, several widely distributed and common Jurassic species (Parainoceramus sensu Cox non Voronetz) remain without a genus to be referred to. We will provisionally use here the name “Parainoceramus” in this sense, until a proper solution is developed (Ros, Damborenea, & Márquez-Aliaga, 2009), and we record its first appearance in the earliest Jurassic. When the material is not well preserved, it is difficult to distinguish between Parainoceramus in this sense and Pseudomytiloides Koschelkina, 1963 (Aberhan, 1998a; Stiller, 2006).

Stratigraphic range.—Lower Jurassic (Hettangian)—Upper Jurassic (Tithonian) (Escobar, 1980; Kelly, 1984). Both Cox and others (1969) and Sepkoski (2002) regarded the first appearance of “Parainoceramus“ to be Upper Triassic following Voronetz (1936), ignoring that Emel'yantsev, Kravtsova, and Puk (1960) had already corrected the dating of the beds from which Voronetz described his specimens from Carnian to upper Permian. We assign the Lower Jurassic (Hettangian) as the oldest record (Escobar, 1980; Damborenea, 1996a), taking into account only the species assigned to this genus sensu Cox (1954). The youngest record is from the Tithonian (Kelly, 1984; Fozy, Kázmér, & Szente, 1994; Liu, 1995).

Paleogeographic distribution.—Tethys, Boreal, and Circumpacific (Fig. 12). “Parainoceramus” was cosmopolitan during the Early Jurassic (especially during the Pliensbachian), but during the Middle and Late Jurassic, it appears to have had a bipolar distribution (possibly Boreal and Austral domains) (Damborenea, 1996b). For further information, see Damborenea (1987b, p. 142–146).

Tethys domain: Early Jurassic: Tibet (Gou, 1985), China (J. Chen, 1982a, 1988); Hettangian of Vietnam (Hayami, 1964); Hettangian—Sinemurian of China (Stiller, 2006); Sinemurian of southern England (Liu, 1995), Turkey (M. A. Conti & Monari, 1991), China (Y. Wang & Smith, 1986).

Boreal domain: Early Jurassic: Sinemurian of northern Siberia (Hallam, 1977).

Circumpacific domain: Early Jurassic: Japan (Hayami, 1960); Hettangian—Sinemurian of Canada (Aberhan, 1998a); Hettangian of Chile (Escobar, 1980).

Paleoautoecology.—B, E, S, Epi, Sed; By. The shell morphology of species attributed to “Parainoceramus“ is variable, and it largely depends on the type of environment. Some species, such as “P.” jinjiensis Chen, 1988, or “P” subtilis (Lahusen), are mytiliform, and they were probably epibyssate (Duff, 1978; Stiller, 2006), but other species, such as “P.” apollo (A. F. Leanza, 1942), are modioliform with a well-developed anterior lobe, and they possibly had an endobenthic mode of life (Damborenea, 1987b). Other genera of the same family, such as Pseudomytiloides, were interpreted as pseudoplanktonic, at least in the early stages (Hayami, 1969a; Etter, 1996). “Parainoceramus” species are found in a wide array of facies types, since they could inhabit different environments, but they are especially abundant in anoxic facies (black shales) (Damborenea 1987b; Harries & others, 1996).

Mineralogy.—Bimineralic (Carter, 1990a, p. 200; Carter, 1990b, p. 330). Outer shell layer: calcite (prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Mytiloides marchaensis Petrova, 1947, p. 130.

Stratigraphic range.—Lower Jurassic (Hettangian)—Middle Jurassic (Aalenian) (Etter, 1996; Stiller, 2006). Cox and others (1969) assigned a Jurassic range to this genus. The oldest record is from Hettangian deposits (Stiller, 2006) and the youngest from Aalenian beds (Etter, 1996). The genus was also mentioned from the Upper Triassic (Norian—Rhaetian) of northeastern Asia (Kurushin, 1990; Polubotko & Repin, 1990), but without indication of the original sources and with no illustrations, so these records remain doubtful.

Paleogeographic distribution.—Tethys (Fig. 12). This genus was especially abundant during the Toarcian. During the earliest Jurassic, it was only reported from the Tethys; but it was also recorded from the Boreal domain by Pliensbachian and Toarcian times (Zakharov & others, 2006). Poulton (1991) reported Pseudomytiloides (?) sp. from ?Hettangian beds of Canada, but it was only one specimen questionably referred to this genus.

Tethys domain: Early Jurassic: Hettangian—Sinemurian of China (Stiller, 2006); Sinemurian of southwestern France (Liu, 1995).

Paleoautoecology.—B-Ps, E, S, Epi, Sed-FaM; By. Pseudomytiloides dubius (J. de C. Sowerby, 1823) is particularly linked to the black shale facies, associated with anoxic conditions, since its abundance decreases as soon as the normal environmental conditions are restored after the early Toarcian extinction event (Harries & Little, 1999; Fürsich & others, 2001; Caswell, Coe, & Cohen, 2009). A pseudoplanktonic mode of life was proposed for this species and P. matsumotoi (Hayami, 1960) (Hayami, 1969a; Tanabe 1983; Seilacher, 1990). This was based on many forms of evidence: they are often found in anoxic facies (Hayami, 1969a), attached to pieces of wood (Hayami, 1969a; Tanabe 1983; Seilacher, 1990), and to ammonoid shells and other bivalves (Tanabe, 1983). However, some authors (e.g., Wignall & Simms, 1990; Etter, 1996) suggested that this interpretation is inadequate since the species abundance is too high to be derived only from floating logs. They proposed that P. dubius had a benthic epibyssate mode of life instead, but it could occasionally live as facultative pseudoplanktonic, with the capacity to attach to various substrates, such as floating objects, and tolerate low oxygen environments (see also Caswell, Coe, & Cohen, 2009). Some authors proposed that certain species of Pseudomytiloides might contain chemosymbionts that would help them live in these inhospitable settings (Harries & Crampton, 1998). Other species, such as P. yinhangensis Chen, 1988, were found in well-oxygenated, quiet, and near-shore environments (Stiller, 2006). The epibyssate mode of life is clearly suggested by their mytiliform shells and their long and flat anteroventral margin (Tanabe, 1983).

Mineralogy.—Bimineralic (Carter, 1990a, p. 200). There are no specific data for Pseudomytiloides. Data used here provided by Carter (1990a) for family Inoceramidae. Outer shell layer: calcite (prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Pseudomytiloides rassochaensis Polubotko, 1968b, p. 61.

Stratigraphic range.—Lower Jurassic (Sinemurian—?Toarcian) (Aberhan, 1998a). The genus was described by Polubotko (1992). It was reported from the Sinemurian of northeastern Russia, and it includes the following species besides the type: A. sinuosus (Polubotko, 1968b), A. kelimiarensis Polubotko, 1992, and A. (?) turomtchensis Polubotko, 1992. Subsequently, Aberhan (1998a) doubtfully reported it from Toarcian beds.

Paleogeographic distribution.—Boreal and Circumpacific (Fig. 12).

Boreal domain: Early Jurassic: Sinemurian of northeastern Russia (Polubotko, 1968b, 1992).

Circumpacific domain: Early Jurassic: Sinemurian—Toarcian of ?Canada (Aberhan, 1998a).

Paleoautoecology.—B, E, S, Epi, Sed; By. Its mytiliform shell indicates an epibyssate mode of life, similar to some living species of the family Mytilidae.

Mineralogy.—Bimineralic (Carter, 1990a, p. 200). No data about Arctomytiloides shell mineralogy and microstructure are available. Data provided for the family Inoceramidae (see any genera in this family).

Type species.—Mytilus hirundo Linnaeus, 1758, p. 706.

Remarks.—Pteroperna Morris & Lycett, 1853 in 1851–1855, is a subgenus, and Rhynchopterus Gabb, 1864, is a junior synonym of Pteria s.l. (see discussion for Pteroperna and Rhynchopterus in Genera not Included, p. 169 and 170).

Stratigraphic range.—Lower Triassic (Olenekian)—Holocene (Hayami, 1975; Beesley, Ross, & Wells, 1998). Pteria ranges from Triassic to Holocene times (Cox & others, 1969; Sepkoski, 2002). The earliest record found is P. ussurica (Kiparisova, 1938) from the Induan (Hayami, 1975). There are some pre-Triassic records (see PBDB, on-line), but most of them were published before Cox and others (1969). M. Wang (1993) described Pteria? yonganensis M. Wang, 1993, from upper Permian beds, but the generic assignment was only tentative, since he had few specimens and their differences with Pteria were important. Tëmkin (2006) doubted the origin of Pteria in the Early Triassic because many so-called winged shells that probably belong to other families (even Bakevelliidae or Isognomonidae) were referred to this genus.

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 13). In the past, Pteria was a widespread genus; today it is common in warm seas (Cox & others, 1969; Beesley, Ross, & Wells, 1998), and was apparently not known from the Austral domain.

Tethys domain: Early Triassic: China (Z. Yang & Yin, 1979; S. Yang, Wang, & Hao, 1986; Ling, 1988; L. Li, 1995; Shen, He, & Shi, 1995; Tong & others, 2006; Komatsu, Huyen, & Chen, 2007); Middle Triassic: Anisian of the Alps (Switzerland) (Zorn, 1971), southern China (Komatsu, Chen, & others, 2004; Komatsu, Akasaki, & others, 2004); Anisian—Ladinian of northern Vietnam (Komatsu, Huyen, & Huu, 2010); Late Triassic: Carnian of Italy (Allasinaz, 1966; Fürsich & Wendt, 1977; Corazzari & Lucchi-Garavello, 1980), Germany (Linck, 1972); Norian of China (Lu, 1981); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Italy (Allasinaz, 1962; Gelati & Allasinaz, 1964; Gaetani, 1970); Early Jurassic: Hettangian of Italy (Allasinaz, 1962), China (J. Yin & McRoberts, 2006); Hettangian—Sinemurian of Italy (Gaetani, 1970); Sinemurian of eastern Asia (Hallam, 1977), Portugal (Liu, 1995).

Circumpacific domain: Early Triassic: Japan (Nakazawa, 1971; Hayami, 1975; Kashiyama & Oji, 2004); Late Triassic: Norian of Japan (Nakazawa, 1964); Early Jurassic: Hettangian of Japan (Hayami, 1975; Kondo & others, 2006; Fraiser & Bottjer, 2007a), ?Chile (Aberhan, 1994a).

Boreal domain: Late Triassic: Carnian of Primorie (Kiparisova, 1972).

Paleoautoecology.—B, E, S, Epi, Sed; By. Extant Pteria species often live attached to corals, usually by a strong byssus (S. M. Stanley, 1970, 1972). In many fossil specimens, the byssal notch is present (e.g., Damborenea, 1987b, Pteroperna sp.) and the shell morphology is similar enough to living species shells to assume they had a similar mode of life. They are often found forming groups of several individuals, probably as the result of a gregarious mode of life, as happens in modern species (S. M. Stanley, 1970).

Mineralogy.—Bimineralic (Carter, 1990b, p. 336, for living species). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Avicula arcuata Münster in Goldfuss, 1835 in 1833–1841, p. 128.

Stratigraphic range.—Lower Triassic (lower Olenekian)—Upper Triassic (?Rhaetian) (Sha & Grant-Mackie, 1996; Newton in Newton & others, 1987). Although many authors assigned it a Middle Triassic (Ladinian)—Upper Triassic (Carnian) range (Cox & others, 1969; Hallam, 1981; Sepkoski, 2002; Tëmkin, 2006), Arcavicula was also mentioned from the Lower Triassic (Sha & Grant-Mackie, 1996) and with some uncertainty from the Norian (Newton in Newton & others, 1987). Newton (in Newton & others, 1987) provisionally referred her specimens to Arcavicula sp. due to the hinge details, but she related them to Rhaetavicula on account of their external similarity. It is also evident that some species were attributed to Pteria regardless of their internal characters. Newton (1988) later confirmed this reference. Laws (1982) mentioned but did not figure Arcavicula sp. from Upper Triassic (upper Norian = Rhaetian, according to Dagys & Dagys, 1994) from Nevada. There are no specific Middle Triassic Arcavicula records, although several authors (e.g., Cox & others, 1969; Hallam, 1981; Sepkoski, 2002; Tëmkin, 2006) mentioned this genus among their materials.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 13).

Tethys domain: Early Triassic: early Olenekian of China (Sha & Grant-Mackie, 1996); Late Triassic: Carnian of southern Alps and Apennines (Italy) (Broglio-Loriga, Ietto, & Posenato, 1993), Alps and Sicily (Diener, 1923; Kutassy, 1931), early Carnian of Lombardy (Italy) (Allasinaz, 1966), southern Alps (Italy) (Bittner, 1895); Norian of ?China (Kobayashi & Tamura, 1983a).

Circumpacific domain: Late Triassic: Norian of Oregon (United States) (Newton & others, 1987; Newton, 1988); Rhaetian of ?Nevada (United States) (Laws, 1982).

Paleoautoecology.—B, E, S, Epi, Sed; By. The presence of anterior auricle and byssal sinus in some specimens, and their external morphology, indicate that species of this genus most likely lived epibyssate or shallowly buried in the sediment in the adult stage, by comparison with living Pterioida (Newton in Newton & others, 1987).

Mineralogy.—Bimineralic (Carter, 1990b, p. 335). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Avicula contorta Portlock, 1843, p. 126.

Remarks.—Cox (1962) pointed out the similarities between Rhaetavicula and Oxytoma, and he proposed that Rhaetavicula could even be a member of the family Oxytomidae, but Rhaetavicula lacks the deep byssal groove located under the right anterior auricle, which is typical of that family. Based on the information provided by the shell mineralogy of Rhaetavicula (calcitic outer layer and alleged aragonitic inner layer), it is probably referable to Pteriidae. Nevertheless, if further studies confirm an inner calcitic layer, it should be referred to the Oxytomidae instead (Cox, 1962). There are no studies on this subject (Carter, 1990a). Previous to 1962, when Cox described this genus, the type species of Rhaetavicula was assigned to different genera: Avicula, Pseudomonotis, Cassianella, and Pteria.

Stratigraphic range.—Upper Triassic (Rhaetian). Rhaetavicula contorta is a Rhaetian guide fossil (see references in paleogeographic distribution). During that stage, it was widely distributed, especially in the Tethys domain.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 13). Though Rhaetavicula was reported from the Austral domain (New Zealand), Cox (1962, p. 594) referred this record to Oxytoma. Although Hallam (1981, 1990) also listed it from Austral regions, the record will not be taken into account here because this information could not be confirmed.

Tethys domain: Late Triassic: Rhaetian of England (Cox, 1962; Castell & Cox, 1975; Warrington & Ivimey-Cook, 1990; Ivimey-Cook & others, 1999; Wignall & Bond, 2008), Italy (Allasinaz, 1962; Sirna, 1968; Bice & others, 1992; McRoberts, 1994), Hungary (Vörös, 1981), Burma (Vu Khuc & Huyen, 1998), southern Tibet (Hallam & others, 2000; J. Yin & Enay, 2000), Iran (Hautmann, 2001b), western Carpathians (Slovakia) (Tomašových, 2004; Michalík & others, 2007), Alps (Austria) (Tomašových, 2006a, 2006b; McRoberts, 2010), Spain (Goy & Márquez-Aliaga, 1998).

Circumpacific domain: Late Triassic: Rhaetian of Nevada (United States) (Cox & others, 1969; Hallam & Wignall, 2000).

Paleoautoecology.—B, E, S, Epi-Un, Sed; By-R. According to Cox (1962), Rhaetavicula lacked a byssal notch, and he assumed that the byssus emerged between the two valves by a narrow gape. Since the shell is strongly inequivalve (convex left valve and flat right valve) and by similarities to living Pterioida, it probably had an epibyssate mode of life. Another possibility is that the byssus was atrophied in adults (and thus the byssal notch is absent), and then it would live reclined on its left valve, similar to members of the family Cassianellidae (Hautmann, 2001b).

Mineralogy.—Bimineralic (Carter, 1990a, p. 206). Outer shell layer: calcite (prismatic). Middle and inner shell layers: aragonite (?).

Type species.—Gervilleia? ogilviae Bittner, 1895, p. 88.

Remarks.—Stefaninia was named by Venzo (1934), but his description did not fulfill the nomenclatorial rules (ICZN Code, 1999), since no type species was assigned and no diagnostic features were given (Stenzel, 1971, p. 1215). Cox in Cox and others (1969, p. 306) designated the type species and provided its diagnosis.

Stratigraphic range.—Middle Triassic (upper Ladinian)—Upper Triassic (Carnian). Bittner (1895) described the type species from the Saint Cassian Formation, regarded as Carnian in age (Fürsich & Wendt, 1977). Cox and others (1969) assigned a Ladinian age, probably on the basis of Venzo's paper (1934; see above).

Paleogeographic distribution.—western Tethys (Fig. 13).

Tethys domain: Middle Triassic: late Ladinian of Italy (Cox & others, 1969); Late Triassic: Carnian of Italy (Bittner, 1895).

Paleoautoecology.—B, E, S, Epi, Sed; By. Its external morphology and the presence of byssal notch indicate a probable byssate mode of life. Possibly, like other members of the family, it spent the early stages of development fixed by the byssus, but adults could have lived partially buried in the sediment. There is no information about the type of sediment in which it was found.

Mineralogy.—Bimineralic (Carter, 1990a, p. 206). There is no information about Stefaninia shell mineralogy or microstructure. We use data provided for the family Pteriidae. Outer shell layer: calcite (simple prismatic). Middle and inner shell layer: aragonite (nacreous).

Neave (1939, p. 385) lists “Miller, 1877, p. 185, pro Bakewellia King, 1848” as author of the genus. Nevertheless, Miller (1877, p. 185) did not indicate he was proposing either an emendation or a replacement name, and already in 1850 King (p. 166–171, 255) spelled it consistently as Bakevellia, although he stated (p. 166, footnote) that the name was dedicated to Mr. Bakewell.

Type species.—Avicula antiqua Münster in Goldfuss, 1835 in 1833–1841, p. 126, non Defrance, 1816.

Remarks.—Several subgenera were proposed within Bakevellia (see Damborenea, 1987b, p. 125–126), but Muster (1995) regarded almost all to be synonyms, considering only two of them to be valid, as also did Cox and others (1969): B. (Bakevellia) King, 1848, and B. (Bakevelloides) Tokuyama, 1959a. The subgenera described for our study interval were Neobakevellia Nakazawa, 1959, Integribakevellia Farsan, 1972, Costibakevellia Farsan, 1972, and Spia Skwarko, 1981 (see list of synonyms for both subgenera in Muster, 1995, p. 29, 42).

Stratigraphic range.—upper Permian—Upper Cretaceous. Cox and others (1969) assigned it a Permian—Upper Cretaceous range. Muster (1995) maintained this range, noting that the first record of the genus is dated as upper Permian. Sepkoski (2002) considered the oldest record to be Carboniferous, but we will not take this into account, since it is based on a personal communication by Yancey to Sepkoski (indicated in Sepkoski, 2002), which has not been published.

Paleogeographic distribution.—Cosmopolitan.

Paleoautoecology.—B, Se, S, Endo, Sed; By. The mode of life of bakevelliids is difficult to identify as that they do not have living representatives to compare with, and the study of the morphology alone does not always provide good results, because morphology traits are sometimes contradictory. It is also helpful to interpret the paleoecology of the environments in which the specimens are found. Most species assigned to Bakevellia are almost equivalve, they have a shallow byssal sinus and an anterior lobe, features that indicate an endobyssate way of life, living with the sagittal plane almost vertical (S. M. Stanley, 1972). This interpretation was proposed by Damborenea (1987b) for Bakevellia (Neobakevellia?) pintadae Damborenea, 1987b, and by Aberhan and Muster (1997) for Bakevellia (Bakevellia) waltoni (Lycett, 1863). However, Seilacher (1984) interpreted Bakevellia subcostata (Goldfuss, 1835 in 1833–1841) as reclined and partially buried in the sediment, resting on its left valve, with the commissure plane being almost horizontal.

Mineralogy.—Bimineralic (Márquez-Aliaga & Martínez, 1990a; Carter, 1990b). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Perna aviculoides J. Sowerby, 1814, p. 147.

Remarks.—Fürsich and Werner (1988, p. 112) argued that there are no substantial differences between Gervillia Defrance, 1820, and Gervillella to consider them as independent taxa, and they included Gervillella as a subgenus of Gervillia. We follow Freneix (1965) and Muster (1995) in treating them as separated genera.

Stratigraphic range.—Lower Jurassic (Hettangian)—Upper Cretaceous (?) (Aberhan, 1998a; Muster, 1995). Several authors extended the range back to the Triassic (e.g., Gillet, 1924; Hayami, 1957a; Freneix 1965; Cox & others, 1969; Geyer, 1973; Lazo, 2003), but none of them justified this statement, and they did not figure any Triassic specimens. All except Geyer (1973) simply listed the stratigraphic range of several genera. Geyer mentioned the presence of Gervillella sp. from the Norian Payandé Formation in Colombia, but he did not figure it. It is possible that some Triassic species assigned to Gervillia should be referred to Gervillella instead, but there is no published reference of their presence in this period. The oldest confirmed record dates from the Hettangian (Aberhan, 1998a), and the youngest from the Upper Cretaceous (Muster, 1995). Sepkoski (2002) assigned the last appearance to the Maastrichtian, but it was not possible to see the original data source. Muster (1995) did not specify the stage, and there is no further information about this topic. However, it is not uncommon to find the genus mentioned from the Lower Cretaceous (Lazo, 2003, 2007a).

Paleogeographic distribution.—western Tethys, Austral, and Circumpacific (Fig. 14). The genus had a particularly wide distribution mainly during the Middle and Late Jurassic (Vörös, 1971; Fürsich & Werner, 1988; Liu, 1995; Muster, 1995; Sha & Grant-Mackie, 1996; Delvene, 2003; Sha, Johnson, & Fürsich, 2004).

Tethys domain: Early Jurassic: Hettangian—Sinemurian of England and Morocco (Liu, 1995).

Austral domain: Early Jurassic: Hettangian—Sinemurian of Southern Andes (Damborenea, 1996a; Damborenea & Lanes, 2007).

Circumpacific domain: Early Jurassic: Hettangian—Sinemurian of Canada (Aberhan & Muster, 1997; Aberhan, 1998a); Sinemurian of Chile (Aberhan, 1994a).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Like most bakevelliids, Gervillella presents features that indicate a semi-infaunal endobyssate mode of life (S. M. Stanley, 1972; Aberhan & Muster, 1997) or so-called mud-sticker (Seilacher, 1984). All species assigned to this genus are almost equivalve, they possess an anterior auricle, and their external morphology is elongate spear-shaped. Thanks to its elongated shape, Gervillella could probably bury deeper than other bakevelliids (S. M. Stanley, 1972; Aberhan & Muster, 1997), similar to members of the family Pinnidae (S. M. Stanley, 1972). Although neither Damborenea (1987b) nor Aberhan and Muster (1997) found evidence in their specimens of a byssal notch, according to Cox (1940), one of the characters that defines the genus is that the anterior auricle extends anteroventrally and is limited in the left valve by a deep groove, which indicates the position of the byssus.

Mineralogy.—Bimineralic (Carter, 1990a, p. 207; Carter, 1990b, p. 336). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Gervillia solenoidea Defrance, 1824a, p. 316.

Stratigraphic range.—Middle Triassic (Ladinian)—Upper Cretaceous (Maastrichtian) (Lerman, 1960; Abdel-Gawad, 1986). Both Cox and others (1969) and Muster (1995) indicated its range as beginning at the Upper Triassic, but there are Middle Triassic records of Gervillia, referred to the species G. joleaudi (Schmidt, 1935) from the Anisian of Israel (Lerman, 1960) and Ladinian of Spain (Márquez-Aliaga, 1985). These were not included in Musters monograph (1995), but Waller and Stanley (2005) indicated that the generic assignation of this species requires revision. However, these authors based their opinion, exposed in the discussion of their new subgenus Gervillaria (Baryvellia), in data from Schmidt (1935), who compared G. joleaudi with Gervillia alberti Credner, 1851. According to Márquez-Aliaga (1985), this last species is a true Bakevellia; therefore, Gervillia joleaudi should be considered as a representative of Gervillia from the Sephardic province of the Tethys domain. With regard to the uppermost stratigraphic occurrence, all agreed that the genus disappeared in the Upper Cretaceous. Within our study interval, we will only consider the subgenus Cultriopsis Cossmann, 1904. Boyd and Newell (1979) doubtfully assigned some of their specimens from the Permian of Tunisia to this subgenus.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 14). Although Escobar (1980) reported Gervillia from Hettangian—Sinemurian beds of Chile, only one of the specimens could be attributed with doubt to this genus (Damborenea, 1987b), so it will not be taken into account in the Austral domain in this temporal range. If the genus is present in this domain, it has occurred since the Pliensbachian.

Tethys domain; Middle Triassic; Anisian of Israel (Lerman, 1960); Ladinian of Spain (Márquez-Aliaga, 1983, 1985; Márquez-Aliaga, Hirsch, & López-Garrido, 1986; Márquez-Aliaga & Martínez, 1990a, 1996; Budurov & others, 1991; Márquez-Aliaga & Montoya, 1991; Martinez & Márquez-Aliaga, 1994; Niemeyer, 2002; Márquez-Aliaga & Ros, 2003); Late Triassic; China (Muster, 1995); Carnian of Italy (Fürsich & Wendt, 1977; Muster, 1995), Spain (Martín-Algarra & others, 1993), Slovenia (Jurkovsek, 1978), China (Wen & others, 1976); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Austria (Tanner, Lucas, & Chapman, 2004); Early Jurassic; early Hettangian of Tibet (China) (J. Yin & McRoberts, 2006); Hettangian—Sinemurian of Vietnam (Sato & Westermann, 1991).

Circumpacific domain; Late Triassic; Japan (Muster, 1995); Carnian of Japan (Tamura & others, 1978); Norian of Oregon (Newton, 1986; Newton & others, 1987); Early Jurassic; Hettangian of Japan (Hayami, 1957a, 1964, 1975; Muster, 1995).

Paleoautoecology.—B-Ps, Se-E, S, Endo-Epi, Sed; By. Some species of Gervillia are morphologically similar to species of Gervillella and Gervillancea (see discussion on their mode of life, p. 40, 44). These two genera are interpreted as having a semi-infaunal endobyssate mode of life (Waller & Stanley, 2005). Formerly, Muster (1995) regarded this mode of life to be unlikely for Gervillia, since it had a very short ligament area that would not be enough to maintain the shell stability. Seilacher (1984) suggested a pseudoplanktonic mode of life for some species of Gervillia, as epibyssate on ammonoids. He called these forms pendent forms. However, other species of Gervillia were interpreted as semi-infaunal endobyssate or mud-stickers (Seilacher, Matyja, & Wierzbowski, 1985). These interpretations are based on the external shell morphology and on the ecological analysis of the depositional environment in which the specimens were found (see Seilacher, 1984; Seilacher, Matyja, & Wierzbowski, 1985). In the Muschelkalk of the Iberian Range (Spain), specimens recorded in marls are common, and they are usually found in semi-infaunal life position. Newton (in Newton & others, 1987) and Damborenea (1987b) interpreted their specimens as epibyssate, but they noted that the shells also had features indicative of a semi-infaunal habit. These are usually found associated with corals.

Mineralogy.—Bimineralic (De Renzi & Márquez-Aliaga, 1980; Carter, 1990a; Márquez-Aliaga & Martínez, 1990a; Martínez & Márquez-Aliaga, 1994). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers; aragonite (nacreous).

Type species.—Mytulites sodalis Schlotheim, 1823 in 1822–1823, p. 112.

Stratigraphic range.—Lower Triassic (Olenekian)—Upper Triassic (Rhaetian) (Hallam, 1981; Dagys & Kurushin, 1985). Cox and others (1969) indicated a Triassic—Middle Jurassic range, although some authors believed Hoernesia disappeared in the Rhaetian (Hallam, 1981, 1990; Hallam & others, 2000). However, Muster (1995, p. 89) extended its range to the Middle Jurassic, because she included Gervillia radians Morris & Lycett, 1853 in 1851—1885, in the synonymy list of Hoernesia sodalis (Schlotheim, 1823 in 1822–1823); besides, she did not consider Hoernesia to be present in the Early Triassic. The first record of Hoernesia dates from the Early Triassic (Dagys & Kurushin, 1985; Posenato, 2008a).

Paleogeographic distribution.—Tethys and Boreal (Fig. 14).

Tethys domain; Early Triassic: Italy (Neri & Posenato, 1985), Yunnan (China) (Guo, 1985); Middle Triassic; Bulgaria (Stefanov, 1942; Encheva, 1969), Spain (Via, Villalta, & Esteban, 1977; Márquez-Aliaga, 1983, 1985; Márquez-Aliaga & Martínez, 1996; Márquez-Aliaga & others, 2001, 2002, 2004; Márquez-Aliaga & Ros, 2002), Italy (Posenato, 2002; Posenato & others, 2002), Germany (Fuchs & Mader, 1980; Hagdorn, 1982; Hagdorn & Simon, 1983, 1991), Poland (Senkowiczowa, 1985; Kaim, 1997), Hungary (Szente, 1997); Anisian of China (Sha, Chen, & Qi, 1990); Anisian—Ladinian of northern Vietnam (Komatsu, Huyen, & Huu, 2010); Ladinian of the Alps (Austria and Italy) (Arthaber, 1908), Germany (Ürlichs, 1978); Late Triassic; China (Cowper-Reed, 1927), Malaysia (Tamura & others, 1975); Carnian of Italy (Laube, 1865), Slovenia (Jurkovsek, 1978); Norian of China (Lu, 1981); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Burma (Healey, 1908), Iran (Repin, 2001), Tibet (J. Yin & Enay, 2000).

Boreal domain: Early Triassic: Olenekian of northern Siberia (Dagys & Kurushin, 1985).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Hoernesia is, characterized by a strongly inequivalve shell and twisted valves, and thus it was interpreted as a so-called twisted recliner by Seilacher (1984). It also has an umbonal shell thickening, so its life position consisted of this area being introduced into the sediment, with the posterior part of the valves sticking out (Savazzi, 1984; Seilacher, 1990; Muster, 1995). The inferred life position is similar to that of Gervillaria alaeformis (J. Sowerby, 1819) (see discussion about the mode of life of this species, below). Seilacher (1990) suggested chemosymbiosis as a functional explanation for this curious life position.

Mineralogy.—Bimineralic (Carter, 1990b, p. 337). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Gervilleia (Cultriopsis) elongata Mansuy, 1919, p. 7.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Carnian) (Diener, 1923; Komatsu, Huyen, & Huu, 2010). Cox and others (1969) referred this genus to the Triassic without further explanation and indicated it is monospecific. According to Diener (1923), the type species was described by Mansuy from the Carnian of Tonkin, which today covers most of Vietnamese northern regions. Later, Vu Khuc and Huyen (1998) mentioned L. elongata (Mansuy, 1919) as being typical from Ladinian beds in the same area, and, recently, Komatsu, Huyen, and Huu (2010) reported it from the Anisian and Ladinian of northern Vietnam.

Paleogeographic distribution.—Eastern Tethys (Fig. 14).

Tethys domain: Middle Triassic: Anisian—Ladinian of northern Vietnam (Komatsu, Huyen, & Huu, 2010); Ladinian of Tonkin (north of Vietnam) (Vu Khuc & Huyen, 1998); Late Triassic: Carnian of Tonkin (Vietnam) (Diener, 1923).

Paleoautoecology.—B, Se, S, Endo, Sed; By. We did not find any figures of the genus; therefore, it is difficult for us to refer it to a particular mode of life, but according to its description in Cox and others (1969), we consider it to be similar to Hoernesia.

Mineralogy.—Bimineralic (Carter, 1990a, p. 206—207). There are no data on Langsonella shell structure. We used data provided for the family Bakevelliidae. Outer shell layer: calcite (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

Type species.—Gervillia hagenowii Dunker, 1846, p. 37.

Remarks.—Cox (1954) described Cuneigervillia and included Edentula Waagen, 1907, p. 96 (non Nitzch, 1820, p. 189) as its synonym. Later, in Cox and others (1969), he regarded Edentula [= Waagenorperna Tokuyama, 1959a, p. 151] as a separate genus and included it into the Isognomonidae. In turn, Tokuyama (1959a) proposed the name Waagenoperna to replace Edentula Waagen, 1907. He pointed to significant differences between the Cuneigervillia type species designated by Cox (1954) (Gervillia hagenowii Dunker, 1846) and some species attributed to Edentula (E. lateplanata Waagen, 1907, and E. triangularis Kobayashi & Ichikawa, 1952). He designated Edentula lateplanata as the type species of Waagenoperna, maintaining the two genera as distinct taxa, relating G. hagenowii to the Bakevelliidae and E. lateplanata and E. triangularis to the Isognomonidae. Muster (1995) decided to include Cuneigervillia with the Isognomonidae, believing that although Cuneigervillia externally seems to be a bakevelliid, it possesses certain characteristics that are typical of the Isognomonidae, such as terminal or sub terminal beaks and a toothless adult hinge. It is difficult to decide because both families share many characteristics, but the lack of teeth in the adult stage is not a critical feature because it also occurs in certain bakevelliids; for example, in some species of Bakevellia (Bakevellia) the dentition is obsolete in adults (Cox & others, 1969, p. 306). The Treatise diagnosis states “hinge teeth present at least in lower growth stages ….” Regarding the beaks, they can either be subterminal (e.g., Aguilerella) or terminal (e.g., Gervillia). Furthermore, Cuneigervillia presents the typical teeth of Bakevellia in juvenile stages. Therefore, according to Cox and others (1969), we include Cuneigervillia in the Bakevelliidae.

Stratigraphic range.—Lower Jurassic (Hettangian)—Lower Cretaceous (?) (Cox & others, 1969). Cox and others (1969) assigned it a lower Liassic to Lower Cretaceous range, since Tokuyama (1959a) referred several Carnian species to Waagenoperna that were initially assigned by Cox (1954) to Cuneigervillia.

Paleogeographic distribution.—western Tethys (Fig. 14).

Tethys domain: Early Jurassic: Europe and northern Africa (Cox & others, 1969); Hettangian of France (Freneix & Cubaynes, 1984), south of England (Warrington & Ivimey-Cook, 1990), Spain (Gómez, Goy, & Márquez-Aliaga, 2005; Márquez-Aliaga, Damborenea, & Goy, 2008a, 2008b; Márquez-Aliaga & others, 2010); Hettangian—Pliensbachian of northwestern Europe (Hallam, 1987); Sinemurian of Portugal (Liu, 1995).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Cuneigervillia was interpreted as a semi-infaunal endobyssate bivalve (S. M. Stanley, 1972), as were most members of Bakevelliidae.

Mineralogy.—Bimineralic (Carter, 1990a, p. 206–207). There are no data on Cuneigervillia mineralogy and shell microstructure. Data provided for the family Bakevelliidae are used here. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Modiola? alaeformis J. Sowerby, 1819, p. 93.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Cretaceous (Turonian) (Komatsu, Chen, & others, 2004; Muster, 1995). Cox and others (1969) assigned this genus a Jurassic–Cretaceous range in Europe, but, since then, new records have extended its stratigraphic range. The oldest record is Anisian (Komatsu, Chen, & others, 2004) and the youngest is Turonian (Muster, 1995).

Paleogeographic distribution.—Tethys, Austral, and Circumpacific (Fig. 14).

Tethys domain: Middle Triassic: Muschelkalk of Germany (Muster, 1995); Anisian of Qingyan (southern China) (Komatsu, Chen, & others, 2004); Late Triassic: southwestern China (Komatsu, Chen, & others, 2004); Rhaetian of Lombardy (Italy) (Muster, 1995), Italian Alps and Vietnam (Hautmann, 2001b), western Carpathians (Slovakia) (Tomašových, 2004), Tibet (China) (J. Yin & Grant-Mackie, 2005); Norian—Rhaetian of Iran (Hautmann, 2001b).

Austral domain: Early Jurassic: Sinemurian of the Andean Basin (Aberhan & Fürsich, 1997); Hettangian—Sinemurian of the Andean Basin (Damborenea & Manceñido, 2005b).

Circumpacific domain: Middle Triassic: Ladinian of western Nevada (Waller & Stanley, 2005); Late Triassic: Norian of southeastern Sonora (Mexico) (McRoberts, 1997a); Early Jurassic: Sinemurian of ?western Canada (Aberhan, 1998a), Chile (Aberhan, 1994a).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Some species, such as Gervillaria alaeformis (J. Sowerby, 1819) (Muster, 1995, fig. 37) and Gervillaria pallas (A. F. Leanza, 1942) (Damborenea, 1987b, fig. 7; Muster, 1995, fig. 43), have a strongly inequivalve and inequilateral shell, with the left valve being more convex than the right, twisted valves, and an elongated posterior auricle. These species were interpreted as having a semi-infaunal endobyssate mode of life, probably supplemented by byssal attachment (Damborenea, 1987b; Aberhan & Muster, 1997). Seilacher (1984, fig. 7) proposed an analogous interpretation for a similar species, Hoernesia tortuosa, including it as a twisted recliner. This category was also used by Aberhan and Muster (1997) for their specimens of G. pallas. Gervillaria (Baryvellia) ponderosa Waller in Waller & Stanley, 2005, was also considered semi-infaunal endobyssate, but this species had a peculiar external morphology, which probably means that its life position was also special (Waller & Stanley, 2005) (see discussion on Gervillancea mode of life, below). However, due to the mytiliform appearance of some species referred to Gervillaria, these were interpreted as epibyssate (S. M. Stanley, 1972). Gervillaria ashcrofiensis (Crickmay, 1930a) (see Muster, 1995, fig. 39) was also thought to be epibyssate, according to its nearly equivalve shell, umbonal thickening, and flat anteroventral area, among other characteristics (see Aberhan & Muster, 1997).

Mineralogy.—Bimineralic (Carter, 1990a, p. 206–207). There are no data on Gervillaria mineralogy or shell microstructure. Data provided for family Bakevelliidae are used here. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Gervillancea coxiella Skwarko, 1967, p. 54.

Stratigraphic range.—Upper Triassic (Carnian—Norian) (Skwarko, 1967). Gervillancea is a monospecific genus only known from Upper Triassic of New Guinea (Skwarko, 1967; Muster, 1995; Waller & Stanley, 2005). Although it was described before the publication of the Treatise (Cox & others, 1969), it was included neither there nor in Sepkoski (2002).

Paleogeographic distribution.—Southern Tethys (Fig. 14). Gervillancea was endemic in the Australian province (according to Damborenea, 2002b) of the Tethys domain. It was only reported from Papua New Guinea (Skwarko, 1967).

Paleoautoecology.—B, Se, S, Endo, Sed; By. One of the most striking features of this genus is its extremely long anterior auricle, which distinguishes it from almost all other genera of Bakevelliidae. According to Waller and Stanley (2005), there are two species, Gervillaria (Baryvellia) ponderosa Waller in Waller & Stanley, 2005, and Gervillia joleaudi (Schmidt, 1935), that also have this feature. These two species, together with Gervillancea coxiella, may be a good example of evolutionary convergence, but, in fact, Gervillia joleaudi lacks an anterior auricle. The external shape of Gervillancea is very asymmetric and inequivalve. None of the specimens figured by Skwarko (1967) bears a byssal notch, but if the species was byssate, like other bakevelliids, the byssus probably emerged from the shell under the anterior auricle. Taking into account that it probably lived anchored to the substrate with the anterior auricle, a strong byssus was not necessarily needed to maintain stability inside the substrate. Pedal and byssal muscle scars indicate that these muscles were strong and able to aid the shell to penetrate up to a third of its dorsal line into the sediment, since the convexity of the shell increases at this point and thus limits the burial depth (see Waller & Stanley, 2005, p. 27—29). The bivalve most probably introduced itself into the sediment during the juvenile stages, since the anterior auricle is comparatively thin and thus inadequate to penetrate the sediment in the adult stage.

Mineralogy.—Bimineralic (Carter, 1990a, p. 206—207). No data are available about the shell of Gervillancea, but it was probably bimineralic, as in other Bakevillidae (J. D. Taylor, Kennedy, & Hall, 1969). Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Songdaella graciosa Vu Khuc, 1977b, p. 51 [182].

Remarks.—Vu Khuc (1977b) assigned Songdaella to the Bakevelliidae, but he indicated that the genus had intermediate characters between this family and the Isognomonidae. Muster (1995) did not include it in her monograph about the family Bakevelliidae and did not comment about its systematic position. In the absence of more information, we include Songdaella in Bakevelliidae.

Stratigraphic range.—Upper Triassic (Norian) (Vu Khuc, 1977b). Songdaella was only recorded from Norian beds (Vu Khuc, 1977b; J. Chen, 1982a; Vu Khuc & Huyen, 1998).

Paleogeographic distribution.—Eastern Tethys (Fig. 14). Songdaella was endemic to southern East Asia (Vu Khuc & Huyen, 1998).

Tethys domain; Norian of northern Vietnam (Vu Khuc, 1977b) and southern China (J. Chen, 1982a).

Paleoautoecology.—B, E, S, Epi, Sed; By. Songdaella is characterized by a mytiliform shell, and some of the specimens figured by Vu Khuc (1977b) are similar to Mytilus. The author related his new genus to Aguilerella according to its external morphology, which was interpreted as epibyssate by S. M. Stanley (1972), due to its external similarity with Mytilus and Myalina.

Mineralogy.—Bimineralic (Carter, 1990a, p. 206—207). There are no data about the shell of Songdaella. We use the data predominant in the family Bakevelliidae. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Perna kobyi de Loriol, 1901, p. 99.

Stratigraphic range.—Upper Triassic (Rhaetian)—Lower Cretaceous (Hauterivian) (J. Yin & McRoberts, 2006; Kozai, Ishida, & Kondo, 2006).

Many authors restricted it to a Lower Jurassic—Upper Jurassic range (Cox & others, 1969; Muster, 1995; Sepkoski, 2002). This range was extended due to new records from the Rhaetian of Tibet (J. Yin & McRoberts, 2006) and from the Hauterivian (Kozai, Ishida, & Kondo, 2006).

Paleogeographic distribution.—Eastern Tethys and Circumpacific (Fig. 14). Although during the study interval it was only reported from eastern Tethys and Austral domains, from Toarcian times it extended also to western Tethys and Boreal regions (see Fürsich, 1982; Liu, 1995; Muster, 1995; J. Yin & Grant-Mackie, 2005; Zakharov & others, 2006).

Tethys domain; Late Triassic; Rhaetian of Tibet (China) (J. Yin, H. Yao, & Sha, 2004; J. Yin & McRoberts, 2006); Early Jurassic; Hettangian of China (J. Chen & Liu, 1981; J. Yin & McRoberts, 2006).

Circumpacific domain: Early Jurassic: Sinemurian of Chile (Aberhan, 1994a; Aberhan & Fürsich, 1997), Canada (Poulton, 1991); Hettangian—Sinemurian of South America (Damborenea, 1996a).

Paleoautoecology.—B, E, S, Epi, Sed; By. Due to its mytiliform aspect, it was thought to be epibyssate (S. M. Stanley, 1972). Aguilerella is one of the few bakevelliids, together with Songdaella, that are interpreted to be epibyssate due to their triangular form, without anterior lobe and with terminal beaks (Damborenea, 1987b). In some species, a gregarious behavior was observed (Fürsich, 1982; Damborenea, 1987b).

Mineralogy.—Bimineralic (Carter, 1990a, p. 206—207). There are no specific data about the shell of Aguilerella. Data provided for the family Bakevelliidae. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Towapteria nipponica Nakazawa & Newell, 1968, p. 59.

Stratigraphic range.—lower Permian (Sakmarian)—Lower Triassic (Induan) (Hayami & Kase, 1977; S. Yang, Wang, & Hao, 1986). Nakazawa and Newell (1968) proposed the genus Towapteria with material from the middle Permian of Japan. Cox and others (1969) did not take it into account in the Treatise, probably due to the proximity of publication. Hayami and Kase (1977) assigned it a Sakmarian—upper Permian range with some doubts. Towapteria was later reported from the Tethyan Early Triassic (see paleogeographic distribution below). Nevertheless, Muster (1995) assigned it an upper Permian, ?Upper Triassic, Middle Jurassic discontinuous range, due to the inclusion of some species previously assigned to Gervillia and Costigervillia (see synonymy list in Muster, 1995, p. 92). She did not see the material personally and the addition of most these species to the synonymy list was done doubtfully due to the lack of internal reliable characters for classification. Furthermore, Muster (1995) did not take into account some Tethyan, Early Triassic species, such as T. scythica (Wirth), among others.

Paleogeographic distribution.—Tethys and ?Circumpacific (Fig. 14).

Tethys domain: late Permian: Changhsingian of Italy (Farabegoli, Perri, & Posenato, 2007); Early Triassic: Induan of Italy (Broglio-Loriga, Neri, & Posenato, 1980, 1986; Broglio-Loriga, Masetti, & Neri, 1982; Neri, Pasini, & Posenato, 1986; Broglio-Loriga & others, 1988, 1990; Posenato, 1988, 2008a), China (S. Yang, Wang, & Hao, 1986; L. Li, 1995; Tong & Yin, 2002; Waller & Stanley, 2005; Komatsu, Huyen, & Chen, 2007).

Circumpacific domain: late Permian: ?Japan (Nakazawa & Newell, 1968; Hayami & Kase, 1977).

Paleoautoecology.—B, E, S, Epi, Sed; By. It is hard to assign a specific life habit to Towapteria, because there are some features indicative of an epibyssate and others of an endobyssate mode of life. Due to its external similarity to Costigervillia Cox & Arkell, 1948 in 1848—1850 (a genus not included here because it first appeared in the Middle Jurassic), we can assume that Towapteria was endobyssate, but its smooth and lob ate anterior auricle and radially ribbed shell indicate otherwise. We suggest it was byssate and probably lived with the anterior part introduced in the sediment. The ribs probably helped to stabilize the shell, as was postulated for Costigervilla by Seilacher (1984).

Mineralogy.—Bimineralic (Carter, 1990a, p. 206–207). No data are available about the shell of Towapteria. Data provided for family Bakevelliidae. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Virgellia coxi Freneix, 1965, p. 64.

Remarks.—Fürsich & Werner (1988) considered Virgellia as subgenus of Gervillia Defrance, 1820, since, in their opinion, it had intermediate features between Gervillia and Gervillella (which they also regarded as subgenus of Gervillia). Following Freneix (1965) and Muster (1995), we regard Virgellia as a separate genus. Freneix (1965) proposed Virgellia and originally included in it three species: V. coxi Freneix, 1965, V. fittoni (Sharpe, 1850), and V. sobralensis (Sharpe, 1850). Later, Muster (1995) added V. simbaiana (Skwarko, 1967) to V. coxi and V. sobralensis (see synonym list in Muster, 1995, p. 94–95).

Stratigraphic range.—Upper Triassic (Carnian)—Upper Jurassic (Kimmeridgian) (Muster, 1995). Cox and others (1969) and Sepkoski (2002) did not take Virgellia into account. The type species was originally described from Callovian sediments, and the original range assigned to the genus was Bajocian to Kimmeridgian (Freneix, 1965). Later, its range was extended by the inclusion of V. simbaiana by Muster (1995). The oldest record of Virgellia is from Carnian beds (Skwarko, 1967, 1981) and the youngest from Kimmeridgian beds (Freneix, 1965). It has not been recorded from the Lower Jurassic.

Paleogeographic distribution.—Southern Tethys (Fig. 14). Although during the interval of time under consideration it was only known from southern Tethys, during the Middle and Late Jurassic it was reported also from Tunisia (Freneix, 1965; Holzapel, 1998) and Portugal (Fürsich & Werner, 1988).

Tethys domain: Late Triassic: Carnian—Norian of Papua New Guinea (Skwarko, 1967, 1981; Muster, 1995).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Virgellia was externally similar to Gervillella and probably had the same mode of life, though slightly less buried into the substrate, as it lacked the Gervillella spear shape but had a more developed anterior lobe (Muster, 1995).

Mineralogy.—Bimineralic (Carter, 1990a, p. 206—207). No data about Virgellia shell mineralogy or microstructure are available. Data provided for the family Bakevelliidae. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Gervilleioperna timoriensis Krumbeck, 1923b, p. 76.

Remarks.—Although Cox and others (1969) and other authors included Gervilleioperna in the Isognomonidae, we assign it to the Bakevelliidae following Damborenea (1987b), noting that it had a pteriform shell and a strong radial carina.

Stratigraphic range.—Lower Jurassic (Sinemurian)—Middle Jurassic (Aalenian) (Aberhan, 1994a; Aberhan & Hillebrandt, 1996). The oldest record of Gervilleioperna is from Sinemurian beds (Aberhan, 1994a). During the Toarcian, its distribution became restricted to the Circumpacific domain (in Chile) (Aberhan & Hillebrandt, 1996).

Paleogeographic distribution.—Circumpacific (Fig. 14). Although Gervilleioperna was present beginning in Sinemurian times, it reached a diversity peak in the Pliensbachian and became extinct during the Aalenian. It is especially abundant in the Tethys domain during the Pliensbachian (Accorsi-Benini & Broglio-Loriga, 1975; Buser & Debeljak, 1994; Liu, 1995; Aberhan & Fiirsich, 1997; Fraser & Bottjer, 2001a, 2001b; Fraser, Bottjer, & Fischer, 2004), while during the Sinemurian, it was only found in the Circumpacific domain. It was also reported from the northern part of the Austral domain during the Pliensbachian (Damborenea, 1987b). Gervilleioperna was not recorded in high paleolatitudes, and it was therefore restricted to warm waters (Damborenea, 1996a). It had a pan-Tethyan distribution, ranging from the Pacific coast (South America) through southern Europe and northern Africa to the eastern Tethys (Timor).

Circumpacific domain; Early Jurassic; Sinemurian of Chile (Aberhan, 1994a; Aberhan & Muster, 1997).

Paleoautoecology.—B, Se, S, Endo, R, Sed; By. Along with Lithiotis, Lithioperna, Cochlearites, and Mytiloperna, Gervilleioperna was a reef builder, especially during Pliensbachian times, replacing the coral reefs of the Late Triassic (Fraser, Bottjer, & Fischer, 2004). Gervilleioperna was interpreted as being reclined, lying on its left valve (Seilacher, 1984; Damborenea 1987b; Fraser, Bottjer, & Fischer, 2004). Buser and Debeljak (1994) interpreted it as epifaunal epibyssate similarly to Recent Isognomon species, but we believe the semi-infaunal endobyssate option is more reasonable, because its left valve is much heavier than the right and it would have easily sunk into the soft sediment (Damborenea, 1987b). Seilacher (1984) interpreted it as a cup-shaped recliner in soft sediments, similar to Gryphaea. Fraser, Bottjer, and Fischer (2004, fig. 10A) agreed, but they classified it as epifaunal. Aberhan and Hillebrandt (1996) suggested that Gervilleioperna (Gervilleiognoma) aurita Aberhan & Hillebrandt was semiinfaunal endobyssate, lying on the umbonal region and the anterior part of its left valve, and with its commissural plane oblique to the substrate surface. Since a byssal notch is observed (Cox & others, 1969, p. 325), it most likely was endobyssate.

Mineralogy.—Aragonitic (Accorsi-Benini & Broglio-Loriga, 1975; Carter, 1990a; Carter, Barrera, & Tevesz, 1998). Accorsi-Benini and Broglio-Loriga (1975) studied the shell of their specimens of Gervilleioperna, but they did not check the mineralogical composition (aragonite or calcite) of the shell layers. Carter (1990a) noted that further analysis is needed to determine whether the outer layer contains prismatic calcite. Outer shell layer: aragonite-calcite (?). Inner shell layer: aragonite (?).

Type species.—Avicula gryphaeata Münster in Goldfuss, 1835 in 1833–1841, p. 127.

Stratigraphic range.—?Permian, Middle Triassic (Anisian)—Upper Triassic (Rhaetian). Cox and others (1969) assigned Cassianella a Triassic and probably Permian range. Ciriacks (1963) and Waterhouse (1987) mentioned Cassianella from the lower and middle Permian (up to Guadalupian), but specimens in both papers were referred to the genus by external morphology only, and in neither reference were internal characters described. Although Ciriacks (1963, p. 31) mentioned Cassianella from the Lower Triassic, we did not find any information about this, and he did not figure any specimens. Cassianella was common from the Anisian to Rhaetian (see paleogeographic distribution).

Paleogeographic distribution.—Cosmopolitan (Fig. 15).

Tethys domain: Middle Triassic: Anisian of southern China (Komatsu, Chen, & others, 2004); Anisian—Ladinian of Bulgaria (Stefanov, 1942), Italy (Posenato, 2008a); Ladinian of Spain (Márquez-Aliaga, 1983, 1985; Márquez-Aliaga, García-Forner, & Plasencia, 2002), Slovakia (Kochanová, Mello, & Siblík, 1975), Israel (Lerman, 1960), Italy (Rossi Ronchetti, 1959); Late Triassic: Sumatra (Krumbeck, 1914), Alps (Austria) (Tomašových, 2006a, 2006b), China (Cowper-Reed, 1927; J. Chen, 1982a; Gou, 1993); Carnian of the Italian Alps (Bittner, 1895; Leonardi, 1943; Fürsich & Wendt, 1977), Carpathians (Bittner, 1901a), Turkey (Bittner, 1891), Spain (Márquez-Aliaga & Martínez, 1996), Israel (Lerman, 1960); Norian of western Caucasus (Ruban, 2006a), China (Wen & others, 1976; J. Chen & Yang, 1983), Singapore (Kobayashi & Tamura, 1968a; Norian—Rhaetian of Iran (Hautmann, 2001b); late Rhaetian ofTibet (J. Yin & McRoberts, 2006), Pamira (Polubotko, Payevskaya, & Repin, 2001), Alps (Italy) (Desio, 1929; McRoberts, Newton, & Allasinaz, 1995), India (Healey, 1908).

Circumpacific domain: Late Triassic: Peru (Körner, 1937), Japan (Kobayashi & Ichikawa, 1949a; Tamura, 1990); Norian of Oregon (United States) (Newton, 1986, 1989; Newton & others, 1987), southwestern Alaska (McRoberts & Blodgett, 2000), Canada (Tozer, 1962, 1970); Rhaetian of Nevada (United States) (Silberling, 1961; Laws, 1982); Norian—Rhaetian of Chile (Chong & Hillebrandt, 1985).

Austral domain: Late Triassic: Carnian of New Zealand (Trechmann, 1918; Marwick, 1953); Norian—Rhaetian of Argentina (Riccardi & others, 1997, 2004; Damborenea & Manceñido, 2012).

Boreal domain: Late Triassic: northern Siberia (Kurushin, 1990; Polubotko & Repin, 1990); Carnian of Primorie (Kiparisova, 1972); Norian—Rhaetian of northeastern Russia (Kiparisova, Bychkov, & Polubotko, 1966).

Paleoautoecology.—B, E, S, Un, Sed; R. Cassianellids are generally interpreted as being reclining bivalves, lying on their left valve on the sediment (Fürsich & Wendt, 1977; Laws, 1982; Newton in Newton & others, 1987; Hautmann, 2001b). Some species, such as C. lingulata Gabb, 1870, and C. angusta Bittner, 1891, were thought by Laws (1982) and Newton (in Newton & others, 1987), respectively, to be byssate, although there is no byssal notch.

Mineralogy.—Aragonitic (Carter, 1990b, p. 338–339; Carter, Barrera, & Tevesz, 1998). Carter, Barrera, and Tevesz (1998) assigned an aragonitic mineralogy for all shell layers to the family Cassianellidae. Previously, Carter (1990b) noted that some species of Cassianella [e.g., C. beyrichi Bittner, 1895, or C. inaequiradiata (Schafhäutl, 1852)] have calcite in the outer shell layer. Cassianella is the only genus of this family for which there are studies of the mineralogy and shell microstructure. Outer shell layer: calcite or aragonite (prismatic). Inner shell layer: aragonite (prismatic).

Type species.—Cassianella (Burckhardtia) boesei Freeh, 1907, p. 334.

Remarks.—According to Alencaster de Cserna (1961), the type species was first referred to ?Pterinea by Burckhardt and Scalia (1905).

Frech (1907) argued that this species was better included in Cassianella on the basis of its characteristics, and he named the subgenus Burckhardtia. But Alencaster de Cserna (1961) suggested that this species is more related to Myophoria Bronn, 1835 in 1834—1838, than to Cassianella Beyrich, 1862, and she included it in the first genus. Following Cox and others (1969), we regard it as a separate genus within the family Cassianellidae due to the presence of obtuse wings, a feature not known among myophorids.

Stratigraphic range.—Upper Triassic (Carnian) (Freeh, 1907). Freeh (1907) described the genus from Carnian beds of Zacatecas (Mexico), and it appears to be endemic in this area and restricted to this age (Burckhardt & Scalia, 1905; Diener, 1923; Alencaster de Cserna, 1961; Cox & others, 1969, Hallam, 1981; Kobayashi & Tamura, 1983a; Barboza-Gudino, Tristán-González, & Torres-Hernández, 1990; Sepkoski, 2002).

Paleogeographic distribution.—Circumpacific (Fig. 15).

Circumpacific domain: Late Triassic: Carnian of Mexico (Burckhardt & Scalia, 1905; Freeh, 1907; Alencaster de Cserna, 1961; Barboza-Gudino, Tristán-González, & Torres-Hernández, 1990).

Paleoautoecology.—B, E, S, Un, Sed; R. Burckhardtia probably had a mode of life similar to Cassianella, but considering that it is almost subequivalve, a semi-infaunal mode of life, similar to Hoernesia, would perhaps be more likely.

Mineralogy.—Aragonitic (Carter, 1990a, p. 207; Carter, Barrera, & Tevesz, 1998). Data provided for family Cassianellidae. There are no studies on the shell of Burckhardtia (see Cassianella mineralogy, p. 46). Outer shell layer: calcite or aragonite (prismatic). Inner shell layer: aragonite (prismatic).

ex Gugenberger, 1935, p. 250

Type species.—Floernesiella horrida Gugenberger, 1935, p. 250.

Remarks.—Gugenberger did not designate a type species for his genus Hoernesiella. Ichikawa (1958, p. 195) designated Hoernesiella horrida as type species, and he claimed the generic authorship under Article 25 c 3 of ICZN (1999). Years later, Cox in Cox and others (1969, p. 312), surely without knowledge of Ichikawa's (1958) paper, noticed the lack of type species, and designated another type species for Hoernesiella: H. carinthiaca Gugenberger, 1935, p. 250, also claiming the generic name authorship (see Stenzel, 1971, p. 1215). Vokes (1980) attributed the authorship to Ichikawa (1958) by priority of type species designation, and this approach is followed here.

Stratigraphic range.—Upper Triassic (Carnian) (Cox & others, 1969). Cox and others (1969), Stenzel (1971), Hallam (1981), and Sepkoski (2002) assigned it a Carnian range. It was not possible to find more information about this genus.

Paleogeographic distribution.—western Tethys (Fig. 15).

Tethys domain: Late Triassic: Carnian of Carinthia (Austria) (Ichikawa, 1958; Cox & others, 1969).

Paleoautoecology.—B, E, S, Un, Sed; R. Similar to Cassianella.

Mineralogy.—Aragonitic (Carter, 1990a, p. 207; Carter, Barrera, & Tevesz, 1998). Data provided for family Cassianellidae. There are no specific studies on the shell of Hoernesiella (see Cassianella mineralogy, p. 46). Outer shell layer: calcite or aragonite (prismatic). Inner shell layer: aragonite (prismatic).

Type species.—Lilangina nobilis Diener, 1908, p. 62.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Carnian) (Cox & others, 1969; Komatsu, Huyen, & Huu, 2010). All sources checked assigned Lilangina to the Carnian (Diener, 1923; Cox & others, 1969; Hallam, 1981; Kobayashi & Tamura, 1983a). However, recently, Komatsu, Huyen, and Huu (2010) reported it from the Anisian and Ladinian.

Paleogeographic distribution.—Eastern Tethys (Fig. 15).

Tethys domain: Middle Triassic: Anisian—Ladinian of northern Vietnam (Komatsu, Huyen, & Huu, 2010); Late Triassic: Carnian of Kashmir (Diener, 1923; Cox & others, 1969; Kobayashi & Tamura, 1983a), China (Wen & others, 1976; Kobayashi & Tamura, 1983a; Sha, Chen, & Qi, 1990).

Paleoautoecology.—B, E, S, Un, Sed; R. Similar to Cassianella.

Mineralogy.—Aragonitic (Carter, 1990a, p. 207; Carter, Barrera, & Tevesz, 1998). Data provided for family Cassianellidae. There are no specific studies on the shell of Lilangina (see Cassianella mineralogy, p. 46). Outer shell layer: calcite or aragonite (prismatic). Inner shell layer: aragonite (prismatic).

Type species.—Reubenia hesbanensis Cox, 1924, p. 63.

Stratigraphic range.—Upper Triassic (Carnian) (Cox, 1924). Cox (1924) described Reubenia from the Carnian beds of Jordan, including two species, the type species and Reubenia attenuata Cox, 1924. All reviewed literature (Kutassy, 1931; Cox & others, 1969; Hallam, 1981; Sepkoski, 2002) assigned it the same stratigraphic range.

Paleogeographic distribution.—western Tethys (Fig. 15).

Tethys domain: Late Triassic: Carnian of Jordan (Cox, 1924).

Paleoautoecology.—B, E, S, Un, Sed; R. Similar to Cassianella.

Mineralogy.—Aragonitic (Carter, 1990a, p. 207; Carter, Barrera, & Tevesz, 1998). Data provided for family Cassianellidae. There are no specific studies on the shell of Reubenia (see Cassianella mineralogy, p. 46). Outer shell layer: calcite or aragonite (prismatic). Middle shell layer: aragonite (nacreous). Inner shell layer: aragonite (prismatic).

Type species.—Gervillia johannisaustriae Klipstein, 1845 in 1843–1845, p. 249.

Stratigraphic range.—Middle Triassic (Ladinian)—Upper Triassic (Carnian) (Allasinaz, 1966; Tamura, 1990). Cox and others (1969) assigned it a Triassic range, without further comments. Sepkoski (2002) assigned it a Triassic (lower Anisian—Carnian) range, allegedly using Hallam (1981) as data source, but Hallam only mentioned it from Ladinian and Carnian times. The published records indicate that the genus was only present in these two Triassic stages.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 15).

Tethys domain: Middle Triassic: Ladinian of Malaysia (Tamura & others, 1975); Late Triassic: Carnian of Italy (Allasinaz, 1966; Fürsich & Wendt, 1977), Spain (Martín-Algarra, Solé de Porta, & Márquez-Aliaga, 1995), Malaysia (Tamura & others, 1975).

Circumpacific domain: Middle Triassic: Ladinian of Japan (Tamura, 1990); Late Triassic: Carnian of Japan (Tamura, 1990).

Paleoautoecology.—B, E, S, Un, Sed; R. Similar to Cassianella.

Mineralogy.—Aragonitic (Carter, 1990a, p. 207; Carter, Barrera, & Tevesz, 1998). There are no studies on the shell of Septihoernesia (see Cassianella mineralogy, p. 46). Outer shell layer: calcite or aragonite (prismatic). Inner shell layer: aragonite (prismatic).

Type species.—Datta oscillaris Healey, 1908, p. 63.

Stratigraphic range.—Upper Triassic (Rhaetian) (Healey, 1908). Healey (1908) described the genus from Rhaetian beds of Burma, and Cox and others (1969) repeated these data. Kobayashi and Tamura (1983a) recorded Datta from several Upper Triassic localities but did not mention stages or the original data source. The statement in Damborenea (2002b, p. 56): “… During the Jurassic and Lower Cretaceous, most genera of Anomiidae, Burmesiidae, Ceratomyopsidae, Cuspidariidae [Dattidae] Diceratidae . …” is an error, and there are no records of Datta from the Jurassic.

Paleogeographic distribution.—Southern Tethys (Fig. 16). The original material is from Burma (Healey, 1908). Later, Kobayashi and Tamura (1983a) also reported the genus from the Late Triassic of Kashmir and Yunnan (China), but they did not indicate the original source, and no information related to these records was found.

Paleoautoecology.—B, E, S, ?, ?. It is difficult to assign a mode of life to this genus since the only information available is from a left valve mold with a possible chondrophore. The shell morphological features suggest it was probably epifaunal.

Mineralogy.—Bimineralic (Carter, 1990a, p. 205). Data provided for superfamily Pterioidea. There are no specific studies on Datta shell. Outer shell layer: calcite (prismatic). Inner shell layer: aragonite (nacreous).

It is often difficult to distinguish between Isognomonidae and Bakevelliidae; good examples are the genera Isognomon (Mytiloperna) von Ihering, 1903, and Gervilleioperna Krumbeck, 1923b, about which there is no agreement among different authors (see discussions for these taxa, below and p. 45). It is quite evident that these two families are phylogenetically related, and consequently setting limits is complicated. A revision of their diagnostic features is needed to establish a consensus. There are also certain difficulties in distinguishing between Inoceramidae and Isognomonidae (see Crampton, 1988).

Lightfoot proposed the name in an anonymous catalogue (1786, authorship determined by Dance, 1962, see also Kay, 1965) spelling the name both as Isognoma and Isognomon, and later Dall, Bartsch, and Rehder (1938, p. 61–62) regarded Isognomon as the original spelling and Isognoma as a misspelling (first revisers action according to Coan, Valentich Scott, & Bernard, 2000, p. 196).

Type species.—Ostrea isognomon Linnaeus, 1764, p. 533 (= Ostrea isognomum in Linné, 1758), by absolute tautonymy (see discussion in Rehder, 1967, p. 6, and Coan, Valentich Scott, & Bernard, 2000, p. 196). This differs from the interpretation by Cox (in Cox and others, 1969, p. 322), which was followed by most authors.

Remarks.—According to Cox and others (1969), there are two subgenera of Isognomon within our interval of study, I. (Isognomon) (but see below) and I. (Mytiloperna). However, some authors noted that probably the latter is more related to bakevelliids than to isognomonids. Mytiloperna was described by H. von Ihering (1903) as a genus based in Perna americana Forbes; Cox (1940) demoted it to a subgenus of Isognomon Lightfoot, 1786, a position maintained in Cox and others (1969) (see Accorsi-Benini & Broglio-Loriga, 1975, for details). There are several reasons to consider that Mytiloperna does not fit into the Isognomonidae. One is the shell microstructure (Broglio-Loriga & Posenato, 1996). Another is that adults had a hinge with teeth, a feature of Bakevelliidae and not of Isognomonidae, which were toothless in the adult stage (Seilacher, 1984; Aberhan, 1998a). However, while pending a good revision of the family, it is advisable to treat Mytiloperna as an isognomonid (Jaitly, Fiirsich, & Heinze, 1995). Additionally, due to a misinterpretation about the correct way of fixation of the type species of Isognomon (see above, and IZCN, 1999, Art. 68.1 and 68.4), most Mesozoic species should be referred to Isognomon (Melina) Retzius, 1788, p. 22, and not to Isognomon (Isognomon), a fact overlooked by most authors, even by those who accepted I. sognomon as type of the genus..

Stratigraphic range.—Upper Triassic (Carnian)—Holocene (Cox & others, 1969). Cox and others (1969) assigned an Upper Triassic to Holocene range to Isognomon (Isognomon) and an Lower Jurassic to Upper Jurassic range to Isognomon (Mytiloperna). Linck (1972) reported the last subgenus from the Carnian, but he included in Mytiloperna (considered at genus level) some modioliform specimens somewhat different from the typical ones. Today there are numerous species living in tropical seas (Beesley, Ross, & Wells, 1998).

Paleogeographic distribution.—Tethys (Fig. 16). During other intervals of geological time, the genus also lived in Circumpacific and Austral regions, especially during the Pliensbachian (see e.g., Damborenea, 1987b; Broglio-Loriga & Posenato, 1996; Aberhan & Fürsich, 1997; Aberhan 1994a, 1998a; Liu, 1999; Fraser, Bottjer, & Fischer, 2004). However, during the temporal interval under consideration, it was only known from the Tethys domain. Holocene species of Isognomon are mainly distributed in tropical seas.

Tethys domain; Late Triassic; Carnian of China (Sha, Chen, & Qi, 1990), Germany (Linck, 1972), southern Italian Alps (Fürsich & Wendt, 1977), Italy (Gelati & Allasinaz, 1964); Norian of Austria (Tichy, 1975), Italy (Terranini, 1958); late Norian of southern China (J. Chen, 1982a); Norian—Rhaetian of Iran, Burma, and Vietnam (Hautmann, 2001b; Fürsich & Hautmann, 2005); Rhaetian of Alps (Italy) (Pozzi, Gelati, & Allasinaz, 1962); Early Jurassic; Hettangian of Japan (Kondo & others, 2006), Europe and northeastern Asia (Hallam, 1977); Hettangian—Toarcian of Japan (Hayami, 1957a, 1975); Sinemurian of Morocco (Liu, 1995), northwestern Europe (Hallam, 1987).

Paleoautoecology.—B, Se, S, Endo, Sed; By. A semi-infaunal endobyssate mode of life seems likely for most Mesozoic species, although some Recent species live epifaunally (S. M. Stanley, 1970, 1972). This disparity in mode of life can be recognized by differences in shell morphology. Living species are often very inequivalve, unlike Mesozoic species, which were equivalve or subequivalve (Hayami, 1957a); there are also differences in shell thickness, the umbonal part being thicker than the ventral part in Mesozoic species (see Fürsich, 1980; Seilacher, 1984; Broglio-Loriga & Posenato, 1996; Fraser, Bottjer, & Fischer, 2004).

Fürsich (1980) analyzed some of the fossil species and observed that, if only shell characters were taken into account, his interpretations were wrong and not viable when he could contrast these results with direct observation of individuals found in life position in the field. All fossil species studied in his work of l980 seem to support a semi-infaunal endobyssate mode of life. Furthermore, fossil species are often found forming groups, and thus they were interpreted as gregarious (Fürsich, 1982; Damborenea, 1987b).

With regard to I. (Mytiloperna), several authors studied its morphology in relation to its mode of life (e.g., Seilacher, 1984; Broglio-Loriga & Posenato, 1996; Fraser, Bottjer, & Fischer, 2004). These last two papers distinguished several Mytiloperna morphotypes with different life habit interpretations, ranging from epifaunal to semi-infaunal.

Mineralogy.—Bimineralic (Carter, 1990b, p. 339). Accorsi-Benini and Broglio-Loriga (1975) and Broglio-Loriga and Posenato (1996) described a fibrous microstructure in the inner shell layer of Mytiloperna sp. specimens. Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Leproconcha paradoxa Giebel, 1856, p. 67.

Remarks.—When Giebel (1856) described the genus, he did not mention its systematic relations, although he indicated that it was intermediate between Ostreacea and Malleacea. Nevertheless, Cox and others (1969) decided to include it with doubts into the Isognomonidae. Looking at the drawings in Giebel (1856, pl. 2,10,13), we can understand why this assignation was more than doubtful. We assume that the ligament pits were the key feature to include Leproconcha in this family, but, unlike the rest of isgnonomonids, it shows an almost equivalve shell and an ostreid external appearance. Lacking any better solution, we follow Cox and others (1969), even knowing it is very unlikely that this genus belongs to this family.

Stratigraphic range.—Middle Triassic (Giebel, 1856). Giebel (1856) described Leproconcha from Muschelkalk of the Germanic Basin. Diener (1923), Kutassy (1931), Cox and others (1969), and Kobayashi and Tamura (1983a) repeated these data, and no further information was found.

Paleogeographic distribution.—western Tethys (Fig. 16).

Tethys domain: Middle Triassic: Muschelkalk of Germany (Giebel, 1856).

Paleoautoecology.—B, E, S, ?, ?. Probably epifaunal.

Mineralogy.—Unknown. There is no information about mineralogy or microstructure of Leproconcha shell. We cannot assign it the mineralogy predominant in the family because we have serious doubts about the family assignation of this genus.

Type species.—Edentula lateplanata Waagen, 1907, p. 97.

Remarks.—Waagenoperna Tokuyama, 1959a was proposed to replace Edentula Waagen, 1907 (non Nitzsch, 1820), and Edentula lateplanata Waagen, 1907, was designated as type species by Tokuyama (1959a). Some years earlier, Cox (1954) had proposed the name Cuneigervillia also to replace Edentula, choosing Gervillia hagenowii Dunker, 1846, as the type species. When Tokuyama (1959a) compared the two type species, he noticed that while Gervillia hagenowii is a bakevelliid (in fact, Cox, 1954, included Cuneigervillia in the family Bakevelliidae), Edentula lateplanata is an isognomonid, like other species attributed to Edentula (E. triangularis Kobayashi & Ichikawa, 1952). Lower Jurassic species also referred to Cuneigervillia by Cox clearly showed that this genus was not objectively the same as Edentula (in fact, they have different type species), and he decided to maintain both names, Cuneigervillia and Waagenoperna (=Edentula), which was followed by Cox and others (1969).

Nakazawa and Newell (1968) proposed a new subgenus within Waagenoperna, W. (Permoperna), and although some authors (Z. Fang, 1982) treated Permoperna at generic level, the original rank is here retained because it does not present substantial differences from Waagenoperna s.s.

Tëmkin (2006, p. 270) erroneously indicated that Waagenoperna was based on W. triangularis (Kobayashi & Ichikawa, 1952).

Stratigraphic range.—lower Permian (Sakmarian)—Upper Triassic (upper Norian) (Hayami & Kase, 1977; J. Chen, 1982a). Cox and others (1969) assigned it a middle Permian—Upper Triassic range. The stratigraphic range should be extended back, since Nakazawa and Newell (1968) reported Waagenoperna (Permoperna) from the lower Permian (Sakmarian). Sepkoski's (2002) range starts from the Guadalupian, which is odd considering that he took his data from Hayami and Kase (1977) and Skelton and Benton (1993), who indicated Sakmarian as the first record. Regarding the upper extension of this genus, J. Chen (1982a, p. 303) quoted Waagenoperna from the upper Norian of southern China, indicating that the association to which it belonged is “the uppermost Triassic bivalve zone in this region.” There are several reports from Hettangian brackish environments of southern China (Sha & Jiang, 2004; Jiang, Sha, & Pan, 2008), although none was corroborated by illustrations or descriptions of the material.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 16).

Tethys domain: Late Triassic: Carnian of southern Alps (Broili, 1904; Tokuyama, 1959a), southern China (Gu & others, 1980); late Norian of China (J. Chen, 1982a).

Circumpacific domain: late Permian: Japan (Nakazawa & Newell, 1968; Hayami, 1975); Middle Triassic: Ladinian of Japan (Tokuyama, 1959a; Hayami, 1975); Late Triassic: Carnian—Norian of Japan (Tokuyama, 1959a; Hayami, 1975).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Although Waagenoperna had a mytiliform shell and most isognomonids were interpreted as epifaunal bivalves, Waagenoperna was thought to be a semi-infaunal endobyssate bivalve, similar to Pinna and some pterineids (S. M. Stanley, 1972). This author relied on morphological evidence, such as the strongly prosocline, slightly inflated, subequivalve shell and the presence of an anterior lobe, features not shared with any other member of the family Isognomonidae.

Mineralogy.—Bimineralic (Carter, 1990a, p. 209). There are no data about the Waagenoperna shell. Information provided for family Isognomonidae. Outer shell layer: calci te (simple prismatic). Middle and inner shell layers: aragonite (nacreous).

The Posidoniidae family members are hardly distinguishable from each other because one of the main diagnostic features is the ligament area, and this is only preserved in exceptional cases. Due to the usually very thin shell, all internal shell characters are frequently destroyed during diagenesis. Waller (in Waller & Stanley, 2005) gathered the families Posidoniidae and Halobiidae Kittl, 1912, in the superfamily Posidonioidea Freeh, 1909. This arrangement is probably more appropriate than the one followed here, but according to Amler (1999), we consider the first family in the superfamily to be Pterioidea Gray 1847, and the second one to be Halobioidea H. J. Campbell, 1994.

Type species.—Posidonia ornati Quenstedt, 1851 in 1851—1852, p. 501.

Remarks.—Following Waller (in Waller & Stanley, 2005), we regard Posidonia Bronn, 1828, as a Paleozoic genus, referring described species from Lower and Middle Triassic to Bositra. We consider Peribositria Kurushin & Trushchelev, 1989, to be a synonym of Bositra (see discussion for Peribositria in Genera not Included, p. 167).

Stratigraphic range.—Lower Triassic (lower Olenekian)—Middle Jurassic (lower Oxfordian) (Waller & Stanley, 2005). Cox and others (1969) assigned it a Jurassic range, but after Waller and Stanley (2005) emended the genus and they transferred species traditionally included in Posidonia from Lower and Middle Triassic, the range was extended back to the Triassic. The problem in the differentiation of both genera is that the main diagnostic characters are in the ligament area, as well as other internal structures, which are often destroyed during diagenesis (Waller in Waller & Stanley, 2005). Fürsich and Werner (1988) reported Bositra from the Upper Jurassic (Kimmeridgian) of Portugal, but their specimens were referred to this genus with some hesitation since the ligament area is not preserved.

Paleogeographic distribution.—Tethys, Circumpacific, and Boreal (Fig. 17). During the Early Triassic, Bositra was distributed mainly in the Boreal domain, extending over the Tethys and Circumpacific domains during the Middle Triassic, to become virtually cosmopolitan during the Early Jurassic (Waller & Stanley, 2005), especially during the Toarcian (Damborenea, 1987b; Aberhan, 1994a, 1998a; Monari, 1994; Liu, 1995; Harries & Little, 1999; Gahr, 2002), coinciding with the peak of early Toarcian extinction. We did not take into account the mention in Waterhouse (2000), because Waller and Stanley (2005) affirm the specimens are more clariids than posidoniids.

Tethys domain; Middle Triassic; Slovenia (Jurkovsek, 1984); Anisian of China (Wen & others, 1976; Ling, 1988; Komatsu, Akasaki, & others, 2004a; J. Chen & Stiller, 2007), western Carpathians (Slovakia) (Kochanová, 1985); Anisian—Ladinian of Vietnam (Vu Khuc & Huyen, 1998); Ladinian of Spain (Márquez-Aliaga, 1983, 1985; Márquez-Aliaga & Ros, 2003); Late Triassic: Carnian of China (Wen & others, 1976), Italy (Fürsich & Wendt, 1977); Norian of China (Sha, Chen, & Qi, 1990).

Circumpacific domain; Middle Triassic; Anisian of Japan (Hayami, 1975), of Nevada (United States) (Waller & Stanley, 2005).

Boreal domain; Early Triassic; Siberia (Kiparisova, 1938; Dagys & Kurushin, 1985), Arctic Archipelago (Canada) (Tozer, 1961, 1962, 1970).

Paleoautoecology.—B, E, S, Un, Sed; R. Bositra was interpreted as a pseudoplanktonic bivalve (S. M. Stanley, 1972) or as nektoplanktonic (Jefferies & Minton, 1965; Hayami, 1969a; Duff, 1975), according to its distribution and morphological characteristics. Other authors rejected these interpretations considering the habit of species assigned to Bositra as benthic (M. A. Conti & Monari, 1992; Etter, 1996).

Etter (1996) did a comprehensive study reviewing all possible modes of life ever attributed to Bositra, demonstrating that a benthic mode of life is entirely plausible and providing arguments to reject the other two options. Since a byssal notch is not observed, a reclined mode of life would have been the most likely (Waller & Stanley, 2005). The reason for its frequent presence in oxygenpoor sedimentary environments should more probably be related to an opportunistic behavior than to a pseudoplanktonic mode of life (Etter, 1996). An updated discussion on the mode of life for Bositra was provided by Caswell, Coe, and Cohen (2009, and see references therein).

Mineralogy.—Bimineralic (Carter, 1990b, p. 340; Waller & Stanley, 2005). Outer shell layer: calci te (homogeneous-prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Amonotis cancellaria Kittl, 1904, p. 736.

Stratigraphic range.—Upper Triassic (Carnian). Amonotis was reported from Carnian beds (Cox & others, 1969; C. Chen & Yu, 1976; Sha, Chen, & Qi, 1990) and apparently also from the Norian, although Norian records lack illustrations or they were dubiously assigned to the genus (Niu, Xu, & Ma, 2003; Tang & others, 2007).

Paleogeographic distribution.—Tethys (Fig. 17). Amonotis was found both in western and eastern Tethys, although some authors (Hallam, 1981; Metwally, 1993) only included European occurrences in their compilations.

Tethys domain; Late Triassic; Carnian of Yugoslavia (Cox & others, 1969), China (C. Chen & Yu, 1976; Sha, Chen, & Qi, 1990).

Paleoautoecology.—B, E, S, Epi, Sed; By. According to S. M. Stanley (1972), almost all posidoniids were epibyssate bivalves, though almost none of the genera shows a sinus or byssal notch, and some of them could be pseudoplanktonic, although there is no evidence that Amonotis was one of them. Therefore, we consider Amonotis as to be an epibyssate bivalve in agreement with Sha, Chen, and Qi (1990), but the possibility of a reclined habit similar to Bositra cannot be ruled out.

Mineralogy.—Bimineralic (Carter, 1990a, p. 211). Data provided for family Posidoniidae. We lack information about the shell of Amonotis. Outer shell layer: calci te (prismatic-homogeneous). Inner shell layer: aragonite (nacreous).

Type species.—Veldidenella dieneri Alma, 1925, p. 118.

Stratigraphic range.—Middle Triassic (upper Anisian—upper Ladinian) (Kochanová, 1985). Cox and others (1969) assigned it a Upper Triassic range, and both Sepkoski (2002) and other compilation papers (e.g., Metwally, 1993) repeated this information. But according to the information published on this monospecific genus, these data appear to be wrong. According to Kutassy (1931), Alma in 1925 described the type species of this genus from Anisian beds of the northern Alps. Tichy (1970), in his catalog of type specimens housed at the Museum of Natural History in Vienna, also indicated Anisian as the age of the type species. Subsequently, Kochanová (1985) reported Veldidenella dieneri from Anisian beds of the western Carpathians and from upper Ladinian beds of the southern Austrian Alps.

Paleogeographic distribution.—western Tethys (Fig. 17).

Tethys domain; Middle Triassic; Anisian of northern Alps (Austria) (Kutassy, 1931), Carpathians (Slovakia) (Kochanová, 1985); Ladinian of northern Alps (Austria) (Kochanová, 1985).

Paleoautoecology.—B, E, S, Epi, Sed; By. Similar to Amonotis.

Mineralogy.—Bimineralic (Carter, 1990a, p. 211). There are no data about Veldidenella mineralogy or shell microstructure. Data provided for the family Posidoniidae. Outer shell layer: calcite (prismatic-homogeneous). Inner shell layer: aragonite (nacreous).

nom. nov. pro Diotis Simonelli, 1884, p. 125, non Schmarda, 1859, p. 5

Type species.—Posidonomya janus Meneghini, 1853, p. 27

Remarks.—Damborenea (1987b, p. 191) noticed that the name Diotis was used previously for a group of worms (Diotis Schmarda, 1859). Years later, Monari (1994) proposed the name Caenodiotis to replace Diotis Simonelli, 1884, in accordance with Article 52 of ICZN (1999). Following Cox and others (1969) and Monari (1994), we include Caenodiotis in Posidoniidae, although given its probable relations to Posidonotis (Damborenea, 1987b), it could perhaps be included in Entoliidae.

Stratigraphic range.—Lower Jurassic (Sinemurian—Pliensbachian) (Monari, personal communication, 2007). According to Cox and others (1969), Diotis was distributed during the early and middle Early Jurassic, but we could not check exactly which stages. Monari (1994) noted its presence from the Pliensbachian in several Italian localities. He also found it in the Sinemurian of the Umbria-Marche region (Monari, personal communication, 2007). We assign the range Sinemurian—Pliensbachian to this genus, until we can determine the age of the units widely referred to as lower Liassic by Cox and others (1969).

Paleogeographic distribution.—western Tethys (Fig. 17). During the Early Jurassic, especially during the Pliensbachian, the genus was distributed in Italy (Monari, 1994), Hungary (Szente, 1990), and Spain (Jiménez de Cisneros, 1923). During the time interval here analized, we only consider the Sinemurian records.

Tethys domain: Early Jurassic: Sinemurian of Italy (Monari, personal communication, 2007).

Paleoautoecology.—B, E, S, Epi, Sed; By. Similar to Amonotis.

Mineralogy.—Bimineralic (Carter, 1990a, p. 211). There are no data about the Caenodiotis shell. Data provided for family Posidoniidae. Outer shell layer: calcite (prismatic-homogeneous). Inner shell layer: aragonite (nacreous).

nom. nov. pro Aulacomya Steinmann, 1881, p. 259, non Mörch, 1853, p. 53

Type species.—Posidonia bronnii Voltz in Zieten, 1833 in 1830– 1833, p. 72.

Remarks.—Steinmannia is very similar morphologically to Bositra De Gregorio, 1886, and Posidonia Bronn, 1828, and the observation of the ligament type is key to discriminating between these genera (multivincular in Steinmannia, alivincular in Bositra, and duplivincular in Posidonia), but its preservation is not common (Waller in Waller & Stanley, 2005). Although Guillaume (1928) and later authors (e.g., Cox & others, 1969; Milova, 1988) included Steinmannia in the Inoceramidae due to the ligament type, Waller (in Waller & Stanley, 2005) thought the ligament of Steinmannia was not of the inoceramid type: “the relatively few ligament pits on the ligament area of Steinmannia bronni (three or four according to Guillaume, 1928, p. 221; three to five according to Milova, 1988, p. 63, pl. 2,1–3) maybe a phylogenetically independent multiplication of the simple alivincular ligament of Bositra possibly functionally associated with increase in size and convexity.“ Following Waller (in Waller & Stanley, 2005), we consider Steinmannia more related to Posidoniidae than Inoceramidae. Some authors included the type species of Steinmannia in Bositra (e.g., Hallam, 1976, 1987; Caswell, Coe, & Cohen, 2009). Multisidonia Polubotko, 1992, p. 60 (type species M. omolonensis Polubotko, 1992, p. 60), distinguished by a greater number of ligamen tal pits, is a possible synonym.

Stratigraphic range.—Lower Jurassic (upper Sinemurian—lower Toarcian) (Guillaume, 1928; Milova, 1988). Cox and others (1969) assigned it a Toarcian range, but Milova (1988) reported a new species, Steinmannia viligaensis Milova, from upper Sinemurian beds (also another from the Pliensbachian, Steinmannia alikiensis Milova, 1988), and the type of Multisidonia is also late Sinemurian in age (Polubotko, 1992). Sepkoski (2002) did not consider this genus.

Paleogeographic distribution.—Boreal (Fig. 17). During the Early Jurassic, especially in the Toarcian, the genus was distributed in the Tethys domain (France, England, Germany, Switzerland) (Guillaume, 1928).

Boreal domain: Early Jurassic: Sinemurian of northeastern Russia (Milova, 1988).

Paleoautoecology.—B, E, S, Un, Sed; R. See mode of life for Bositra (p. 50).

Mineralogy.—Bimineralic (Carter, 1990a, p. 211). There are no data about the shell of Steinmannia. Data provided for family Posidoniidae. Outer shell layer: calcite (prismatic-homogeneous). Inner shell layer: aragonite (nacreous).

Type species.—Posidonia aranea Tozer, 1961, p. 102.

Remarks.—Waterhouse (2008) proposed Ellesmerella based on P. aranea, included it in the family Aulacomyellidae Ichikawa, 1958, and considered it to be related to Bositra. McRoberts (2010) suggested it could be better placed into Posidoniidae or Halobiidae. Provisionally, we include Ellesmerella in the Posidoniidae.

Stratigraphic range.—Lower Triassic (upper Olenekian) (Tozer, 1961). The monospecific genus Ellesmerella was only reported from the Olenekian stage (Tozer, 1961, 1962, 1970; Vozin & Tikhomirova, 1964; Tozer & Parker, 1968; Waterhouse, 2008; McRoberts, 2010). It has a very short stratigraphical range (uppermost Olenekian) (McRoberts, 2010).

Paleogeographic distribution.—Boreal (Fig. 17).

Boreal domain: Early Triassic: late Olenekian of Arctic Archipelago (Canada) (Tozer, 1961), Svalbard (Norway) (Tozer & Parker, 1968), British Columbia (Tozer, 1962, 1970), northeastern Siberia (Vozin & Tikhomirova, 1964).

Paleoautoecology.—B, E, S, Un, Sed; R. Similar to Bositra.

Mineralogy.—Bimineralic (Carter, 1990a). There are no data about the shell of Ellesmerella. Data provided for family Posidoniidae and/ or Halobiidae.

In our study interval, there are two genera belonging to Pinnidae: Pinna Linnaeus, 1758, and Atrina Gray, 1842, p. 83 [1840, p. 151, nom. nud.]. These two genera are morphologically very similar in their juvenile stages, but adults are differentiated mainly by the presence of a median shell carina, which is associated with the separation of the internal nacreous layer into two lobes in Pinna and is absent in Atrina (Cox & others, 1969; Waller & Stanley, 2005). Cox and others (1969) assigned a Carboniferous—Holocene range to Pinna (Pinna) and a Middle Jurassic—Holocene range to Atrina. However, many specimens assigned to Pinna (Pinna) from beds older than Middle Jurassic do not have this median carina, and thus they should probably be referred to Atrina or some Paleozoic genera (Pteronites M'Coy, 1844, Aviculopinna Meek, 1864, or Meekopinna Yancey, 1978) (see Waller & Stanley, 2005, p. 29). In the absence of a review on this subject, we assign provisional stratigraphic ranges for both genera.

Type species.—Pinna rudis Linnaeus, 1758, p. 707.

Stratigraphic range.—?Lower Triassic—Holocene (Nakazawa, 1961). Although, as already mentioned, Cox and others (1969) assigned it a range from the Carboniferous, we could not locate any record of specimens attributed to this age except in the Treatise. A specimen of Pinna (Pinna) costata Phillips from the Carboniferous of Belgium was figured in Cox and others (1969, p. 282), but this specimen does not show the typical carina, and therefore it is not supposed to belong to Pinna (Waller & Stanley, 2005). R. Zhang and Yan (1993) reported the genus from the Carboniferous, but they did not illustrate or describe the material. The oldest positive records are from the Lower Triassic. Nakazawa (1961) figured Pinna muikadaniensis Nakazawa, 1961 (p. 267; plate 13,14), and, although in the description he did not mention the median carina, he said: “… parting mediate distinct but weak in the umbonal half and obsolete in the rear part, deviating towards the an tero-ventral side …” and the figure shows evidence of a true carina. Seguí (1999, p. 21, fig. 1), in the description of his specimen of Pinna bascoi Seguí, 1999, from Ladinian of Spain, said: “There is an edge signal that starting from the apex disappears at about 2/3 of the height. This edge divides the shell into two parts.” This edge can be seen in his figures and seems to correspond with the carina. We doubtfully consider Nakazawa's (1961) Lower Triassic record as valid, since the material is not well preserved and we cannot be sure that it actually belongs to Pinna.

Paleogeographic distribution.—Tethys, Circumpacific, and Austral (Fig. 18). Although Pinna had a cosmopolitan distribution during our study interval, Recent species are restricted to tropical and subtropical seas (Cox & others, 1969). No records were located from the Boreal domain.

Tethys domain; Early Triassic: China (F. Wu, 1985); Middle Triassic: Ladinian of Spain (Seguíacute;, 1999); Late Triassic: southern China (Gou, 1993); Carnian of Slovenia (Jelen, 1988), southern Alps (Italy) (Fürsich & Wendt, 1977), Lombardy (Italy) (Allasinaz, 1964, 1966), Germany (Linck, 1972); Norian of Australia (Grant-Mackie, 1994); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Burma (Healey, 1908), Alps (Austria) (Winkler, 1861), Tibet (China) (J. Yin & McRoberts, 2006), Pamir (Afghanistan) (Polubotko, Payevskaya, & Repin, 2001), Hungary (Vörös, 1981), Italy (Allasinaz, 1962; Sirna, 1968); Early Jurassic: Hettangian of Tibet (China) (J. Yin & McRoberts, 2006), England and Morocco (Liu, 1995), Italy (Sirna, 1968), France (Martin, 1860); Sinemurian of Portugal, Spain, England, France, and Morocco (Liu, 1995).

Austral domain: Late Triassic: Carnian of New Zealand (Trechmann, 1918; Marwick, 1953); Early Jurassic: Hettangian—Sinemurian of Argentina (Damborenea, 1996a; Damborenea & Manceñido, 2005b); Sinemurian of Argentina (Damborenea & Lanes, 2007).

Circumpacific domain: Early Triassic: Japan (Nakazawa, 1961; Hayami, 1975); Late Triassic: Norian of Chile (Hayami, Maeda, & Ruiz-Fuller, 1977); Early Jurassic: Sinemurian of Canada (Aberhan, 1998a).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Depending on the species, Pinna currently lives more or less with the anterior half of the shell buried in the sediment as endobyssate, with a strong byssus attached to fragments of rocks or other objects, such as sea grass roots (García-March, 2005), although some were found epibyssate on hard substrates (S. M. Stanley, 1970). Regarding fossil species, there are many examples of Pinna in upright position, similar to living species (e.g., Fürsich, 1980, 1982; Damborenea, 1987a). It is rare to find complete fossil specimens; only the anterior parts, which are buried in life, are usually found. More detailed information about its mode of life can be found in Yonge (1953) and Seilacher (1984), among many others.

Mineralogy.—Bimineralic (Yonge, 1953; Carter, 1990a; García-March, 2005; García-March, Márquez-Aliaga, & Carter, 2008). Outer shell layer: calci te (prismatic simple). Inner shell layer: aragonite (nacreous).

Gray, 1840, p. 151, nom. nud.

Type species.—Pinna nigra Dillwyn, 1817, p. 325.

Stratigraphic range.—Middle Triassic (Anisian)—Holocene (Stiller, personal communication, 2008). Although Cox and others (1969) assigned it a range from the Middle Jurassic, Waller (in Waller & Stanley, 2005) reported Atrina from the Ladinian. Also Stiller, in his doctoral thesis (Stiller, personal communication, 2008), reported it from the Anisian. Although, as noted, it may have appeared before, we will take this well-documented record as its first appearance. In addition, Waller and Stanley (2005, p. 29–30) noted that Carboniferous Pinnidae could possibly be referable to Atrina and not to Pinna.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 18). Although in the past Atrina was regarded as a cosmopolitan genus, this is not the case for the time interval here considered. Its distribution was surely greater than the one mentioned below, because many species attributed to Pinna may belong to Atrina instead, but there are no specific data for the study interval.

Circumpacific domain: Middle Triassic: late Ladinian of Nevada (United States) (Waller & Stanley, 2005).

Tethys domain: Middle Triassic: Anisian of China (Stiller, 2001, personal communication, 2008).

Paleoautoecology.—B, Se, S, Endo, Sed; By. Atrina living species are semi-infaunal bivalves that live endobyssate, attached by a strong byssus to rock fragments or other materials embedded in the sediment, with the commissure plane being almost vertical, similar to Pinna. Unlike Pinna, which lives with two-thirds of its shell into the sediment, Atrina lives almost completely buried (García-March, Márquez-Aliaga, & Carter, 2008). The same mode of life is assumed for Mesozoic specimens. The external shell spines were interpreted by S. M. Stanley (1970) as protection against breakage of the exposed portion of the shell, rather than a defensive device as in other bivalves.

Mineralogy.—Bimineralic (Carter, 1990a; Garcia-March, 2005). Outer shell layer: calcite (simple prismatic). Inner shell layer: aragonite (nacreous).

Type species.—Pecten simplex Phillips, 1836, p. 212.

Remarks.—Newell (1999, p. 4) rejected Palaeolima because the material of the type species was lost and topotypes were not available. On the other hand, Waller and Stanley (2005, p. 32) stated that “Dickins (1963, p. 91), however, had earlier addressed this problem and designated a neotype of Phillips's species, specifically the specimen figured by Hind (1903 in 1896–1905, p. 19, fig. 26) from Little Island, County Cork, Ireland.” According to these authors, Palaeolima remains valid.

Stratigraphic range.—Upper Devonian (?Fammenian)—Upper Triassic (Norian) (Lu, 1981; Waller & Stanley, 2005). Cox and others (1969) assigned it a Carboniferous—Late Triassic range. Following Waller and Stanley (2005), the range is extended back to the Upper Devonian. The youngest records are from the Upper Triassic of China (Lu, 1981; J. Chen, 1982a; Lu & Chen, 1986).

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 19). Palaeolima had an almost cosmopolitan distribution during the Paleozoic, especially during the Carboniferous—Permian (until the Guadalupian) interval (Yancey, 1985; Gonzalez, 1992; Hoare, 1993; Nakazawa, 1999, 2002; Sterren, 2000, 2004; Cisterna & Sterren, 2003; Waller & Stanley, 2005). During the Triassic, it is found only from the Tethys and Circumpacific domains.

Tethys domain; late Permian; Kashmir (India) (Brookfield, Twitchett, & Goodings, 2003), China (Y. Zhang, 1981; M. Wang, 1993; L. Li, 1995); Early Triassic; China (Ling, 1988); Middle Triassic; Anisian of southern China (Komatsu, Akasaki, & others, 2004); Late Triassic; China (J. Chen, 1982a; Lu & Chen, 1986; Gou, 1993); Carnian of Italy (Corazzari & Lucchi-Garavello, 1980); Norian of China (Lu, 1981).

Circumpacific domain; Middle Triassic; Ladinian of Nevada (United States) (Waller & Stanley, 2005).

Paleoautoecology.—B, E, S, Epi, Sed; By. Living members of the family Limidae live epibyssate or reclined on the substrate or fixed by a slender byssus that may break, allowing occasional swimming (S. M. Stanley, 1970). From his observations of living species, S. M. Stanley (1970) concluded that good swimmers are often equivalve with symmetrical, equally sized auricles, and they have a large umbonal angle. In terms of external shell morphology, Palaeolima can be compared to the species Lima lima (Linnaeus, 1758), which lives epibyssate with a strong byssus. But the species assigned to Palaeolima lack a byssal notch. Other species, such as Lima scabra (Born, 1778) and Lima hians (Gmelin, 1791), are fairly symmetrical, live epibyssate with a weak byssus that can break, and swim occasionally (S. M. Stanley, 1970). Palaeolima has a rather symmetrical shell, and the auricles are of equal size, but the umbonal angle does not normally exceed 80° (from illustrations in the literature). We assume that Palaeolima lived epibyssate, as did P. scabra, although it is very unlikely that it could swim.

Mineralogy.—Bimineralic (Carter, 1990b, p. 345). Outer shell layer: calcite (simple prismatic). Middle and inner shell layers; aragonite (cross-lamellar).

Type species.—Aviculolima jaekeli E. Philippi, 1900, p. 622.

Remarks.—Although Aviculolima is externally similar to Pteria, Cox and others (1969) included it in the Limidae with doubts. Having no further information, we follow these authors in their allocation.

Stratigraphic range.—Middle Triassic (Anisian) (Diener, 1923). The only information we have about Aviculolima was given by Diener (1923) and Cox and others (1969). In both papers, the authors limit themselves to transcribing data from the original paper in which the genus was proposed. The genus was reported from the Lower Muschelkalk of northern Germany (probably Anisian).

Paleogeographic distribution.—western Tethys (Fig. 19). According to available information, the genus appears to be endemic to northern Germany.

Tethys domain; Middle Triassic; Lower Muschelkalk of northern Germany (Diener, 1923).

Paleoautoecology.—B, E, S, Epi, Sed; By. Given its external resemblance to Pteria, probably it was an epifaunal and byssate bivalve, although the generic diagnosis does not mention byssal structures.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). There is no information about Aviculolima shell. Data provided for family Limidae. Outer shell layer: calcite (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Badiotella schaurothiana Bittner, 1895, p. 201. (See notes in Bittner, 1895, p. 200, and Cox & others, 1969, p. 386, related to the nomenclatural status of this genus and its type species).

Stratigraphic range.—Middle Triassic (Ladinian)—Upper Triassic (Carnian) (Diener, 1923). Although Cox and others (1969) assigned it a Ladinian range, there is evidence that the genus was also present in the Upper Triassic (see Bittner, 1895; Broili, 1904; Diener, 1923). Sepkoski (2002) assigned it a Ladinian-Carnian range, following the compilation made by Hallam (1981). The youngest records are from Carnian beds (see paleogeographic distribution).

Paleogeographic distribution.—Tethys (Fig. 19).

Tethys domain; Middle Triassic; China (Lu & Chen, 1986); Ladinian of the Alps (Broili, 1904; Cox & others, 1969); Late Triassic; Carnian of the Alps (Bittner, 1895; Broili, 1904; Diener 1923), China (Gou, 1993).

Paleoautoecology.—B, E, S, Epi-Un, Sed; By-R. Like all members of this family, Badiotella was an epifaunal bivalve. Byssal structures are not reported in published literature, so it possibly lived slightly reclined or fixed by a weak byssus.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). There are no data about Badiotella mineralogy or shell microstructure. Information provided for family Limidae. Outer shell layer: calcite (prismatic). Inner shell layer: aragonite (nonnacreous).

Type species.—Pecten subauriculata Montagu, 1808, p. 63.

Remarks.—Limatula and Limea Bronn, 1831, are genera with living representatives and conservative morphology. Even in Recent species, there is some confusion about which taxa should be referred to one genus or the other (Allen, 2004), and this distinction is much more complicated with fossil specimens.

Stratigraphic range.—Middle Triassic (Ladinian)—Recent. Cox and others (1969) assigned it a Triassic—Holocene range. The oldest record is Ladinian (Tamura, 1973); we did not find any records from the Lower Triassic, or from the Lower Jurassic, although from Toarcian times onward, it was fairly common throughout the Jurassic (Hallam, 1976, 1977, 1981; Fürsich, 1982; Pugaczewska, 1986; Komatsu, Saito, & Fürsich, 1993; Liu, 1995; Sha and others, 1998; J. Yin & Grant-Mackie, 2005).

Paleogeographic distribution.—Tethys, Circumpacific, and Austral (Fig. 19).

Tethys domain; Middle Triassic: Ladinian of Malaysia (Tamura, 1973); Late Triassic: Rhaetian of Italy (Chiesa, 1949), Hungary (Vörös, 1981).

Circumpacific domain: Late Triassic: Norian of Japan (Tokuyama, 1959b; doubtful record also in Nakazawa, 1963).

Austral domain: Late Triassic: Carnian of New Zealand (Trechmann, 1918).

Paleoautoecology.—B, E, S, Epi, FaM; By-Sw. Some living species, such as Limatula strangei (G. B. Sowerby, 1872), live among rocks and corals, and they are able to swim (Beesley, Ross, & Wells, 1998). They have equivalve and slightly inequilateral shells and subequal auricles. The shell morphology remained practically unchanged from the Triassic to the present (Allen, 2004); we assume that Mesozoic species had similar modes of life. Limatula probably lived byssate most of the time and reclined on the substrate, with the anterior part down (Fürsich, 1982).

Mineralogy.—Bimineralic (Carter, 1990b, p. 345). Outer shell layer: calci te (prismatic). Inner shell layer: aragonite (?).

Type species.—Ostrea strigilata Brocchi, 1814, p. 571.

Remarks.—The only subgenus considered by Cox and others (1969) in our study interval is Limea (Eolimea) Cox in Cox and others, 1969, p. 389, with a Middle Triassic range. From the Middle Triassic to the Miocene, when Limea (Limea) appears, there is a long time interval without records of this genus. This was noticed by Dhondt (1989), who also noted that Pseudolimea Arkell in Douglas & Arkell, 1932, which ranges from Triassic to Cretaceous, was distinguished from Limea mainly by the shape of the ribs. Moreover, other subgenera of Limea, such as Isolimea or Eolimea, are differentiated by their strong ornamentation. Dhondt noted that Pseudolimea was very similar to Limea and it could fill this time gap, and she included it as a subgenus of Limea. This arrangement is followed here.

Stratigraphic range.—Middle Triassic (Anisian)—Holocene (Cox & others, 1969). The stratigraphic range of Limea recognized here is the same as in Cox and others (1969). The oldest record is from Anisian times (Kaim, 1997).

Paleogeographic distribution.—Cosmopolitan (Fig. 19).

Tethys domain: Middle Triassic: Poland (Kaim, 1997); Anisian western Caucasus (Russia) (Ruban, 2006a); Ladinian of Spain (Márquez-Aliaga, 1983; Pérez-López, 1991; Pérez-López & others, 1991; López-Gómez & others, 1994; Márquez-Aliaga & Martínez, 1996; Márquez-Aliaga, García-Forner, & Plasencia, 2002), Italy (Rossi Ronchetti, 1959); Late Triassic: Norian of southern China (J. Chen & Yang, 1983); Early Jurassic: Hettangian of northern Alps (Austria) (Golebiowski, 1990); Hettangian—Sinemurian of England (Liu, 1995), Spain (Calzada, 1982); Sinemurian of France, Portugal, and Morocco (Liu, 1995), Turkey (M. A. Conti & Monari, 1991).

Circumpacific domain: Late Triassic: Carnian of Japan (Nakazawa, 1952; Hayami, 1975); Norian of Oregon (United States) (Newton in Newton & others, 1987), Nevada (United States) (Laws, 1982); Norian of Chile (Hayami, Maeda, & Ruiz-Fuller, 1977); Rhaetian of Chile (Chong & Hillebrandt, 1985); Early Jurassic: Hettangian—Sinemurian of western Canada (Aberhan, 1998a; Aberhan, Hrudka, & Poulton, 1998), Chile (Aberhan, 1994a).

Austral domain: Late Triassic: Carnian of New Zealand (GrantMackie, 1960); Rhaetian of New Zealand (MacFarlan, 1998) and Argentina (Damborenea & Man ceñido, 2012); Early Jurassic: Hettangian—Sinemurian of Neuquén Basin (Argentina) (Damborenea, 1996a; Damborenea & Manceñido, 2005b), New Zealand (MacFarlan, 1998).

Boreal domain: Early Jurassic: Hettangian—Sinemurian of ?Greenland (Liu, 1995).

Paleoautoecology.—B, E, S, Epi, Sed; By. Limea is a long-ranging genus that exhibits a conservative morphology throughout its history (Allen, 2004). The Recent species of this genus live mainly in deep water, and it was proposed that the extinct species also lived mostly in this type of environment (Dhondt, 1989). Limea species probably lived as epibyssate and reclined on one of the valves (Fürsich, 1982), similar to living species.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). There are no data about Limea shell. Data provided for family Limidae. Outer shell layer: calci te (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Mysidioptera ornata Salomon, 1895, p. 117.

Remarks.—Two subgenera are considered in the study interval, M. (Mysidioptera) and M. (Pseudacesta) Waagen, 1907, p. 113.

Stratigraphic range.—Lower Triassic (Olenekian)—Upper Triassic (Rhaetian). Cox and others (1969) assigned it a Lower Triassic—Upper Triassic range, and this is maintained here. Mysidioptera was not abundant in the Triassic, but it had a climax during Ladinian and Carnian; and although it was scarce during the Rhaetian, it lived to the end of the stage, when it became extinct.

Paleogeographic distribution.—Cosmopolitan (Fig. 19).

Tethys domain: Middle Triassic: Anisian of China (Wen & others, 1976; Lu & Chen, 1986; Sha, Chen, & Qi, 1990; Komatsu, Chen, & others, 2004; Komatsu, Akasaki, & others, 2004), Malaysia (Tamura & others, 1975), Swiss Dolomites (Zorn, 1971), Italian Dolomites (Posenato, 2008b), Israel (Lerman, 1960), northern Vietnam (Komatsu, Huyen, & Huu, 2010); Ladinian of Alps (Austria) (Salomon, 1895), north of Vietnam and Thailand (Vu Khuc & Huyen, 1998), Malaysia (Tamura, 1973), Lombardy (Italy) (Rossi Ronchetti, 1959), northern Vietnam (Komatsu, Huyen, & Huu, 2010); Late Triassic; China (Gou, 1993); Carnian of southern Alps (Bittner, 1895, 1900; Salomon, 1895; Broili, 1904; Allasinaz, 1966; Fürsich & Wendt, 1977; Posenato, 2008a, 2008b), Carpathians (Slovakia) (Bujnovsky, Kochanová, & Pevny, 1975; Kochanová, Mello, & Siblík, 1975), Jordan (Cox, 1924); Rhaetian of Tibet (China) (Hallam & others, 2000), East of the Alps (Austria) (Tomašových, 2006a, 2006b).

Circumpacific domain; Early Triassic; Olenekian of Japan (Nakazawa, 1961; Hayami, 1975); Late Triassic; Japan (Hayami, 1975), Norian of Oregon (Newton in Newton & others, 1987), Norian of Sonora (Mexico) (Damborenea in Damborenea & González-León, 1997).

Austral domain; Late Triassic; Carnian of New Zealand (Waterhouse, 1960).

Boreal domain; Late Triassic; Carnian of Arctic area of British Columbia (Canada) (Tozer, 1962, 1970).

Paleoautoecology.—B, E, S, Epi, Sed; By. The external shell morphology of different species attributed to Mysidioptera indicates an epibyssate habit, since most show a byssal notch. It could live on both hard and soft substrates (Newton in Newton & others, 1987). They were reported from a variety of facies, as they are thought to have colonized different environments (Damborenea in Damborenea & González-León, 1997).

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). There are no data about Mysidioptera shell mineralogy. Data provided for family Limidae. Outer shell layer: calci te (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Plagiostoma gigantea J. Sowerby, 1814, p. 176.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Cretaceous (Maastrichtian) (Abdel-Gawad, 1986; Komatsu, Chen, & others, 2004). Cox and others (1969) assigned it a Middle Triassic—Cre—taceous range. However, Sepkoski (2002) considered it to be from the Lower Triassic (Induan), indicating that data were taken from Abdel-Gawad (1986), but this author only mentioned Plagiostoma from the Cretaceous. This datum is wrong, since Plagiostoma was not present before the Middle Triassic (see Paleogeographic distribution, below), and it may have derived from Lower Triassic Mysidioptera (Bittner, 1895; Waller & Stanley, 2005). Dagys and Kurushin (1985) reported Plagiostoma aurita (Popov) and Plagiostoma popovi Kurushin in Dagys & Kurushin, 1985, from the Lower Triassic, but the figured specimens have little in common with the diagnosis of the genus Plagiostoma.

Paleogeographic distribution.—Cosmopolitan (Fig. 19).

Tethys domain; Middle Triassic; Hungary (Szente, 1997), Poland (Kaim, 1997); Anisian of Germany (Hautmann, 2006a), southern China (Sha, Chen, & Qi, 1990; Komatsu, Chen, & others, 2004), Switzerland (Zorn, 1971); Ladinian of Sardinia (Italy) (Posenato, 2002; Posenato & others, 2002), Malaysia (Tamura, 1973; Tamura & others, 1975); Late Triassic: China (J. Chen, 1982a; Gou, 1993), Oman (R. Hudson & Jefferies, 1961); Carnian of Malaysia (Tamura & others, 1975), Lombardy (Italy) (Allasinaz, 1966); Norian of Himalaya (Tibet, China) (J. Yin, Enay, & Wan, 1999), southern China (Wen & others, 1976; Sha, Chen, & Qi, 1990), northwestern China (Lu, 1981); Norian—Rhaetian of Iran and the Alps (Hautmann, 2001b); Rhaetian of eastern Alps (Austria) (Tomašových, 2006a, 2006b), Tibet (China) (Hautmann & others, 2005; J. Yin & McRoberts, 2006), Hungary (Vörös, 1981), Lombardy (Italy) (Allasinaz, 1962); Early Jurassic; Hettangian of southern England (Ivimey-Cook & others, 1999), Tibet (China) (Hautmann & others, 2005; J. Yin & McRoberts, 2006), Italy (Gaetani, 1970); Hettangian—Sinemurian of England and France (Liu, 1995), Lombardy (Italy) (Allasinaz, 1962); Sinemurian of Caucasus (southwestern Russia) (Ruban, 2006b), Portugal and Morocco (Liu, 1995).

Circumpacific domain; Middle Triassic; Ladinian of Nevada (United States) (Waller & Stanley, 2005); Late Triassic; Japan (Kobayashi & Ichikawa, 1949a; Tokuyama, 1959a); Carnian of Japan (Hayami, 1975); Norian of Oregon (United States) (Newton in Newton & others, 1987; but see Waller & Stanley, 2005); Early Jurassic; ?Mexico (Damborenea in Damborenea & González-León, 1997); Hettangian—Sinemurian of western Canada (Aberhan, 1998a), Mexico and Texas (Liu, 1995), northern Chile (Aberhan, 1994a); Sinemurian of Japan (Hayami, 1975; Hayami in Sato & Westermann, 1991).

Austral domain; Early Jurassic; Sinemurian of Neuquén Basin (Argentina) (Damborenea, 1996a; Damborenea & Manceñido, 2005b).

Boreal domain; Late Triassic; Carnian of Primorie (Kiparisova, 1972).

Paleoautoecology.—B, E, S, Epi, Sed; By. Like most limids, Plagiostoma was probably an epibyssate bivalve. Although no description pointing to a byssal notch was found, we assume that the byssus would have emerged below the anterior auricle. We cannot rule out that it could eventually swim, but this is unlikely due to the shell thickness (Seilacher, 1984); a reclining habit on its broad anterior base is more likely.

Mineralogy.—Bimineralic (Carter, 1990a, p. 215; Carter, 1990b, p. 345). Outer shell layer: calci te (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Serania seranensis Krumbeck, 1923a, p. 218.

Stratigraphic range.—Upper Triassic (Norian—Rhaetian) (Hautmann, 2001b). According to Kutassy (1931), Serania was proposed by Krumbeck (1923a) on the basis of material from Norian beds of Indonesia and Persia. Cox and others (1969) assigned it a Norian age, as did also Sepkoski (2002), based on Hallaras (1981) data. It was subsequently reported also from Rhaetian beds (Hautmann, 2001b).

Paleogeographic distribution.—Eastern Tethys (Fig. 19). Serania was a monospecific genus endemic for the eastern Tethys.

Tethys domain; Late Triassic; Norian of Indonesia and Persia (Kutassy, 1931); Norian—Rhaetian of Iran (Hautmann, 2001b).

Paleoautoecology.—B, E, S, Epi, Sed; By. Like most members of family Limidae, Serania was probably an epibyssate bivalve, similar to Plagiostoma (Hautmann, 2001b). Serania seranensis shows a deep byssal notch (see Cox & others, 1969, p. 392), which implied a strong byssus.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). There are no data about the shell of Serania. Data provided for family Limidae. Outer shell layer: calci te (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Lima (Tirolidia) haueriana Bittner, 1895, p. 202.

Stratigraphic range.—Middle Triassic (Ladinian)—Upper Triassic (Carnian) (Diener, 1923). Cox and others (1969) assigned a Middle Triassic—Upper Triassic range. Bittner (1895) proposed Tirolidia from Ladinian and Carnian beds of the southern Alps. Diener (1923) and Kutassy (1931) provided the same data. Little else could be found, except that Hallam (1981) assigned it a Ladinian—Carnian range in western Tethys, and thus this genus seems to be endemic to the southern Alps.

Paleogeographic distribution.—western Tethys (Fig. 19).

Tethys domain: Middle Triassic: Ladinian of Southern Alps (Bittner, 1895); Late Triassic: Carnian of Southern Alps (Bittner, 1895).

Paleoautoecology.—B, E, S, Epi, Sed; By. Tirolidia is slightly inequilateral and has unequal auricles, so it is not a good candidate to be a swimmer. We assign it an epibyssate mode of life, similar to other members of this family.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). No specific data about Tirolidia mineralogy and shell microstructure are known. Data provided for family Limidae. Outer shell layer: calci te (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Lima antiquata J. Sowerby, 1818, p. 25.

Stratigraphic range.—Middle Triassic (Ladinian)—Lower Cretaceous (Aptian) (Hayami, 1965; Waller & Stanley, 2005). Cox and others (1969) considered it to be a Jurassic genus (Liassic—Baj ocian), but, since then, new records have expanded its range. The oldest record of Antiquilima is from Ladinian beds of Nevada (Waller & Stanley, 2005) and the youngest from Lower Cretaceous beds (Aptian) (Hayami, 1965).

Paleogeographic distribution.—Cosmopolitan (Fig. 19). According to Damborenea (2000), Antiquilima probably originated in the Eastern Pacific and subsequently it spread to the Tethys, which agrees with the data found about the genus.

Tethys domain: Late Triassic: Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of the Alps (Austria) (Tomašových, 2006a, 2006b), Tibet (China) (J. Yin & McRoberts, 2006), western Carpathians (Slovakia) (Tomášových, 2004); Early Jurassic: Hettangian—Sinemurian of England (Liu, 1995); Sinemurian of France (Vörös, 1971; Liu, 1995), Apennines (Italy) (Monari, 1994).

Circumpacific domain: Middle Triassic: Ladinian of Nevada (United States) (Waller & Stanley, 2005); Late Triassic: Norian of northern Chile (Hayami, Maeda, & Ruiz-Fuller, 1977), Oregon (United States) (Newton, 1986; Newton in Newton & others, 1987); Early Jurassic: Hettangian—Sinemurian of northern Chile (Aberhan, 1994a); Sinemurian of Canada (Aberhan, 1998a), Japan (Hayami, 1975).

Austral domain: Early Jurassic: Sinemurian of Argentina (Damborenea, 1996a; Damborenea & Manceñido, 2005b; Damborenea & Lanes, 2007).

Boreal domain: Late Triassic: Carnian of Primorie (Kiparisova, 1972); Norian of northeastern of Asia (Kurushin, 1990; Polubotko & Repin, 1990); Norian—Rhaetian of eastern Siberia (Kiparisova, Bychkov, & Polubotko, 1966), northeastern Russia (Milova, 1976); Early Jurassic: Hettangian of northeastern Asia (Kurushin, 1990; Polubotko & Repin, 1990), northeastern Russia (Milova, 1976).

Paleoautoecology.—B, E, S, Epi, Sed; By. In most species, a byssal notch is present (e.g., specimens described in Hayami, Maeda, & Ruiz-Fuller, 1977; Newton in Newton & others, 1987; Hautmann, 2001b), and most likely it was an epibyssate bivalve as in the rest of the limids. According to Newton (in Newton & others, 1987), Antiquilima could sever the byssus and swim for short distances, as do some modern species of the family Limidae. However, due to its external morphology, it was probably not a good swimmer.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215; Waller & Stanley, 2005). Outer shell layer: calcite (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Ostracites pectiniformis von Schlotheim, 1820, p. 231.

Stratigraphic range.—Upper Triassic (upper Rhaetian)—Lower Cretaceous (?Valanginian). Cox and others (1969) assigned it a Jurassic (Liassic)—Lower Cretaceous (Neocomian) range. Sepkoski (2002) considered that it originated in the lower Hettangian following Hallam (1977, 1987). The origin of this genus was regarded as Hettangian for a long time (Hallam, 1977, 1987, 1990), but recently J. Yin, H. Yao, and Sha (2004) and J. Yin and McRoberts (2006) found Ctenostreon in layers transitional between the Rhaetian and Hettangian. These Himalayan records were dated as Rhaetian, because they were associated with the ammonoid Choristoceras (J. Yin, H. Yao, & Sha, 2004). We ignore to what part of the Neocomian Cox and others (1969) referred for the last record. The youngest record of the genus dates from Valanginian times (Császár & Turnšek, 1996), but specimens were neither figured nor described, so we tentatively consider this as the last appearance.

Paleogeographic distribution.—Tethys, Austral, and Circumpacific (Fig. 19).

Tethys domain: Late Triassic: Rhaetian of southern China (J. Yin, H. Yao, & Sha, 2004; J. Yin & McRoberts, 2006); Early Jurassic: Hettangian of Tibet (China) (J. Yin & McRoberts, 2006; J. Yin & others, 2007).

Austral domain: Early Jurassic: Hettangian—Sinemurian of the Neuquén Basin (Argentina) (Damborenea, 1996a; Damborenea & Manceñido, 2005b).

Circumpacific domain: Early Jurassic: Sinemurian of Japan (Hayami, 1975), Chile (Aberhan, 1994a).

Paleoautoecology.—B, E, S, Epi, Sed; By. Ctenostreon is regarded as an epibyssate bivalve, although the byssal notch is not always evident and sometimes it is even absent. Its shell is thick compared with other members of this family; we assume that it would not need a very strong byssus. Seilacher (1984) suggested that it is one of those limids for which a swimming mode of life is excluded, due to its thick shell and presence of spines; it was probably a pleurothetic reclined bivalve.

Mineralogy.—Bimineralic (Cox & others, 1969; Carter, 1990a, p. 215). No specific data about Ctenostreon mineralogy and shell microstructure is known. Information provided for family Limidae. Outer shell layer: calcite (prismatic). Inner shell layer: aragonite (non-nacreous).

Type species.—Gryphaea arcuata Lamarck, 1801, p. 398.

Remarks.—Newell and Boyd (1970, 1989, 1995) discussed the external morphological similarity between Pseudomonotis and Gryphaea (see fig. 47 in Newell & Boyd, 1995). Frequently, these genera can only be distinguished by the shell microstructure and which valve is attached to the substrate (right and left respectively) (Newell & Boyd, 1995). Many of the Pseudomonotis records from Triassic and Jurassic could actually belong to Gryphaea, since Pseudomonotis is now regarded as a strictly Paleozoic genus, and it is not an ostreoid.

Stratigraphic range.—Upper Triassic (Carnian)—Upper Cretaceous (Campanian) (McRoberts, 1992; Newell & Boyd, 1989). Stenzel (1971) considered that Gryphaea was present in the Upper Triassic of the Boreal domain and had a worldwide distribution for most of the Jurassic (Hettangian—Oxfordian). New records changed the observed stratigraphic range of this genus; Gryphaea was reported from Upper Triassic beds, from the Carnian (McRoberts, 1992) in the Paleopacific eastern margin, in addition to the Boreal regions. It had not been found anywhere in upper Norian and Rhaetian beds, so McRoberts (1992) interpreted it as a Lazarus taxon that reappeared in the Hettangian stage, but Rubilar (1998) reported Gryphaea from the Norian—Rhaetian of Chile.

The youngest record is from the Upper Cretaceous (Newell & Boyd, 1989). Although there are some papers that mentioned Gryphaea up until the Pleistocene, they are not taken into account as they are bio-stratigraphic studies and they do not describe or figure the listed material.

Paleogeographic distribution.—Cosmopolitan (Fig. 20).

Tethys domain; Early Jurassic: Tibet (China) (Gou, 2003); Hettangian of Italy (Gaetani, 1970); Hettangian—Sinemurian of France (Liu, 1995; Nori & Lathuilière, 2003), England, Spain, Portugal, and Morocco (Liu, 1995).

Circumpacific domain; Late Triassic; Carnian—Norian of Canada, Oregon, and Nevada (United States) (McRoberts, 1992), northern and southern Alaska (McRoberts, 1992; McRoberts & Blodgett, 2000); Norian of Chile (Hayami, Maeda, & Ruiz-Fuller, 1977); Norian—Rhaetian of Chile (Rubilar, 1998); Early Jurassic: Hettangian of Chile (Aberhan, 1994a); Sinemurian of Chile (Steinmann, 1929; Chong & Hillebrandt, 1985; Hillebrandt, 1990; Aberhan, 1994a; Malchus & Aberhan, 1998; Rubilar, 1998), Canada (Poulton, 1991).

Austral domain; Early Jurassic; Sinemurian of Argentina (Damborenea & Manceñido, 2005b; Damborenea & Lanés, 2007).

Boreal domain; Late Triassic; Arctic area of Siberia (Kiparisova, 1954), northeastern Russia (Milova, 1976); Carnian of Arctic Island (Canada) (Tozer, 1970); Carnian—Norian of Primorie (Kiparisova, 1972); Early Jurassic; Hettangian of northeastern Russia (Milova, 1988).

Paleoautoecology.—B, E, S, Un, Sed; R. Some species of Gryphaea lived cemented to the substrate during the juvenile stages, but they often changed to a reclined life habit in the adult stage (Fürsich & others, 2001). Seilacher (1984) interpreted certain Gryphaea species as being cup-shaped recliners, living on soft substrates: they probably rested on their left valve, which is strongly convex and thick, unlike the flat and smooth right valve. The left valve was used to anchor the shell to soft sediments. Gryphaea would thus live epifaunally or partially buried. The specimens are usually found in fine-grained sediments (clay, marl) that are characteristic of low-energy marine environments (Lewy, 1976). The shell morphology of Gryphaea, as in other ostreids, is strongly influenced by the environment. Nori and Lathuilière (2003) proved that several factors (temperature, oxygen level, and humidity) were responsible for the different morphologies.

Mineralogy.—?Bimineralic (Carter, 1990a, p. 232). Although the shell microstructure of Triassic specimens is not known, Jurassic specimens have a prismatic outer shell layer and a foliated inner shell layer, both being calcitic (Carter, 1990a). However, McRoberts and Carter (1994) found that middle and inner layers of G. nevadensis were originally of nacreous microstructure (aragonite).

Type species.—Umbrostrea emamii Hautmann, 2001a, p. 361.

Remarks.—Hautmann (2001a) proposed Umbrostrea to include some specimens from the Upper Triassic of Iran that attached by the left valve (consensual basis for defining the true oysters), built reefs, and possessed an inner foliated shell microstructure and aragonitic inner shell layer (data considered as preliminary by the author). He proposed two new species, Umbrostrea emamii and Umbrostrea iranica, and tentatively considered Umbrostrea? aff. parasitica (Krumbeck, 1913) within the genus. Subsequently, Márquez-Aliaga and others (2005) examined a sample of hundreds of specimens attributed to Enantiostreon difforme (Goldfuss, 1833 in 1833–1841) [=Ostracites cristadifformis Schlotheim, 1820] and Enantiostreon spondyloides (Schlotheim, 1820) from the Lower and Upper Muschelkalk (Middle Triassic, Anisian—Ladinian) of the Germanic Basin, from levels equivalent to those from where the Enantiostreon species were described, attributed by these authors to real oysters. The authors accepted that the first record of ostreids from those levels was by Seilacher (1954), who classified some specimens attached by their left valve to Plagiostoma shells as Alectryonia (=Lopha), but with Enantiostreon morphology. Seilacher (1954) relied on the kind of so-called twisting of the valves and on the antimarginal pattern of the shell folds. This last criterion was developed by Checa and Jiménez-Jiménez (2003b) for cemented bivalves, and it is characteristic of ostreids. In the same paper, Márquez-Aliaga and others (2005) studied the Hispanic Muschelkalk (Ladinian) specimens attributed to E. difformis by Márquez-Aliaga (1985), on which microstructural studies were performed (De Renzi & Márquez-Aliaga, 1980; Márquez-Aliaga & Martínez, 1990b; Márquez-Aliaga & Márquez, 2000). In these studies, the authors verified the presence of foliated and calcitic outer shell layer and an inner shell layer replaced by sparite of possible aragonitic origin; this type of microstructure is characteristic of ostreids. However, the absence of internal features in all the studied specimens did not solve the controversial problem of the origin of the oysters. Thus, several replies to this proposal were generated, including other evolutionary aspects (see discussion in Márquez-Aliaga & others, 2005; Hautmann, 2006b; Checa & others, 2006; and Malchus, 2008). Other authors, like Ivimey-Cook and others (1999) and J. Yin and McRoberts (2006), preferred to include the species Enantiostreon difforme within Terquemia Cox, 1964. Here we provisionally accept the criteria of Márquez-Aliaga and others (2005).

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Rhaetian) (Hautmann, 2001a; Márquez-Aliaga & others, 2005). Hautmann (2001a, 2001b) assigned it a Norian—Rhaetian range. Accepting the species assigned by Márquez-Aliaga and others (2005) into Umbrostrea, the range extends from the Middle Triassic, with the origin of U. cristadifformis and U. spondyloides being in Anisian times.

Paleogeographic distribution.—Tethys (Fig. 21).

Tethys domain: Middle Triassic: Anisian of Poland (Kaim, 1997), Bulgaria (Budurov & others, 1993), Hungary (Szente, 1997); Ladinian of Sardinia (Márquez-Aliaga & others, 2000; Posenato, 2002), Spain (Márquez-Aliaga, 1985; Márquez-Aliaga & Martínez, 1996); Late Triassic: Norian of Indonesia (Diener, 1923); Norian—Rhaetian of Iran (Hautmann, 2001a, 2001b; Fürsich & Hautmann, 2005), Rhaetian of England (Ivimey-Cook & others, 1999), ?Rhaetian of Tibet (China) (J. Yin & McRoberts, 2006).

Paleoautoecology.—B, E, S, C, Sed; C. Although Hautmann (2001a, 2001b) considered that Umbrostrea lived cemented to the substrate by the left valve, the species U. cristadifformis and U. spondyloides could attach by either valve (Márquez-Aliaga & others, 2005). It lived forming small reefs in fully marine environments and was associated with corals, brachiopods, and other bivalves (Hautmann, 2001a).

Mineralogy.—Bimineralic (De Renzi & Márquez-Aliaga, 1980; Carter, Barrera, & Tevesz, 1998; Hautmann, 2001a). In the diagnosis of Umbrostrea, Hautmann (2001a) indicated that the species attributed to this genus are characterized by a regular simple prismatic outer shell layer of calcite, a middle shell layer of foliated calcite, and an aragonitic inner shell layer of unknown microstructure. Umbrostrea cristadifformis had a foliated calcitic outer shell layer and an aragonitic inner shell layer (De Renzi & Márquez-Aliaga, 1980). According to Carter, Barrera, and Tevesz (1998), U. spondyloides (upper Muschelkalk, Ladinian, southwestern Germany) had an aragonitic inner shell layer and calcitic middle and upper shell layers, the last with regular to homogeneous and irregular prismatic microstructures. Outer shell layer: calcite (simple prismatic—foliated). Middle shell layer: calcite (ifoliated). Inner shell layer: aragonite (?nacreous).

Type species.—Ostrea solitaria J. de C. Sowerby, 1824, p. 105.

Remarks.—Palaeolopha Malchus, 1990, is regarded a junior synonym of Actinostreon (see discussion under Palaeolopha, Genera not Included, p. 166).

Stenzel (1971) considered Actinostreon as a subgenus of Lopha, and this was followed by most authors. However, Malchus (1990) included Actinostreon, together with his new genus Palaeolopha, in his new family Palaeolophidae, and he regarded Actinostreon as an independent genus different from Lopha. Checa and Jiménez-Jiménez (2003b) included the species Enantiostreon difforme (Goldfuss, 1833 in 1833–1841) [=Ostracites cristadifformis Schlotheim, 1823 in 1822–1823] in Actinostreon, since Malchus (1990) included this species in Palaeolopha, and they followed the synonymy proposed by Hautmann (2001a, p. 359), i.e. Actinostreon =Palaeolopha Malchus, 1990). Subsequently, Márquez-Aliaga and others (2005) included the species cristadifformis in Umbrostrea Hautmann, 2001a.

Stratigraphic range.—Upper Triassic (Rhaetian)—Upper Cretaceous (Maastrichtian) (Chiplonkar & Badve, 1977; Hautmann, 2001a). Stenzel (1971) assigned it a Jurassic—Cretaceous range; these data were incorporated by Sepkoski (2002), who added Maastrichtian as the last appearance, but he did not indicate the original source. The oldest records are from Rhaetian (Ivimey-Cook & others, 1999; Hautmann, 2001a). Actinostreon was very well represented throughout the Jurassic, and there are very few records from the Cretaceous. The youngest record is the species Lopha (Actinostreon) diluvian (Linnaeus) from Maastrichtian beds (Chiplonkar & Badve, 1977), quoted also by Ayyasami (2006) from the Turonian, both in southern India, although the latter is a biostratigraphic paper. However, this species is frequently assigned to Lopha, although according to Malchus (1990), Lopha had a Tertiary origin.

Paleogeographic distribution.—Tethys, Circumpacific, and Austral (Fig. 21).

Tethys domain; Late Triassic; Rhaetian of England (Penarth Group) (Ivimey-Cook & others, 1999), Austria (Hautmann, 2001a).

Circumpacific domain; Late Triassic; Norian of Mexico (Damborenea in Damborenea & González-León, 1997); Early Jurassic; Hettangian—Sinemurian of Mexico and Texas (United States) (Liu, 1995), Andes (Chile and Argentina) (Damborenea, 1996a, 2000); Sinemurian of Chile (Aberhan, 1994a; Sha, Smith, & Fürsich, 2002), Japan (Toyora Group) (Hayami, 1975).

Austral domain; Early Jurassic; Hettangian—Toarcian of the Andes (Chile and Argentina) (Damborenea, 1996a, 2000).

Paleoautoecology.—B, E, S, C, Sed; C. Actinostreon was a cemented bivalve that attached itself to the substrate by the left valve. Usually it formed clusters in high-energy marine environments (Sha, Smith, & Fürsich, 2002). It could attach to inorganic substrates and also to the shells of other organisms. Most often it attached by cementation to individuals of the previous generation, but it was also found on other bivalves (e.g., Modiolus in Ivimey-Cook & others, 1999) or solitary (Machalski, 1998). According to Sha (2002), ostreids have planktotrophic larvae that are responsible for their wide dispersion.

Mineralogy.—Calcitic (Carter, 1990a; Hautmann, 2001a). According to Carter (1990a), Lopha haidingeriana (Emmrich, 1853) had predominantly foliated middle and inner shell layers, but a thin prismatic outer shell layer may also be present. Hautmann (2001a) found no trace of an aragonitic inner shell layer in one of his Actinostreon haidingerianum (Emmrich, 1853) specimens, and in a tangential section, he observed thin layers of foliated structure. The aragonite is limited to the miostracum and ligostracum (Hautmann, 2001a). The shells show a typical structure with biconvex chambers (Malchus, 1998). Outer shell layer: calcite (?prismatic). Middle and inner shell layers; calcite (regular foliated).

Type species.—Ostrea sublamellosa Dunker, 1846, p. 41.

Stratigraphic range.—Upper Triassic (Carnian)—Upper Cretaceous (Cenomanian) (Hayami, 1975; Carter, 1990a). Stenzel (1971) reported Liostrea as being present in the Norian of Siberia and from the Rhaetian to the Jurassic of Europe. Subsequently, the genus was reported from Carnian beds of Japan (Hayami, 1975). The oldest record is from the Ladinian (Waller in Waller & Stanley, 2005), but, in these specimens, some diagnostic characters are not seen, and thus a definite identification is not possible. This record is regarded as dubious Liostrea until more material is found in the area. If confirmed, the origin of Liostrea goes back to the Middle Triassic. According to Carter (1990a), the youngest record is Liostrea oxiana Romer from the Cretaceous (Cenomanian) (Seeling & Bengtson, 1999).

Paleogeographic distribution.—Cosmopolitan (Fig. 21).

Tethys domain; Late Triassic: Carnian of China (J. Chen, 1982a), ?Italy (Gaetani, 1970); Rhaetian of Tibet (China) (?Hautmann & others, 2005; J. Yin & McRoberts, 2006), England (Ivimey-Cook & others, 1999), Italy (Gaetani, 1970); Early Jurassic; Hettangian ofTibet (China) (?Hautmann & others, 2005; J. Yin & McRoberts, 2006), England (Liu, 1995; Ivimey-Cook & others, 1999), Italy (Gaetani, 1970); Sinemurian of England and Portugal (Liu, 1995).

Circumpacific domain; Late Triassic; Carnian of ?Peru (Cox, 1949); Norian of Oregon (United States) (Newton, 1986; Newton in Newton & others, 1987); Norian—Rhaetian of Chile (Rubilar, 1998); Early Jurassic; Sinemurian of Japan (Hayami, 1975), Chile (Rubilar, 1998).

Austral domain; Late Triassic; Rhaetian of Argentina (Riccardi & others, 2004; Damborenea & Manceñido, 2012).

Boreal domain; Late Triassic; Norian of Siberia (Stenzel, 1971); Early Jurassic; Hettangian—Sinemurian of Greenland (Liu, 1995).

Paleoautoecology.—B-Ps, E, S, C, Sed-FaM; C. Liostrea cemented to the substrate by the left valve, like the other ostreids. Unlike Gryphaea, it has a large cementation area. Liostrea cemented itself to hard substrates, bivalve shells, or other organisms (Newton in Newton & others, 1987). It was usually found forming reefs during the Jurassic (Fürsich, Palmer, & Goodyear, 1994). However, the species Liostrea erina (d'Orbigny) was found cemented to ammonoids (Leioceras) in the Middle Jurassic Opalinum Clay (Switzerland), so it is supposed to have been pseudoplanktonic (Etter, 1996). This author found evidence indicating that the cementation was achieved when the ammonoids were still alive (see fig. 4 in Etter, 1996). Other species, such as L. plastica (Trautschold) from the Upper Jurassic of Greenland, were also found cemented to ammonoids, but it was not possible to determine whether the cementation was pre- or postmortem for the ammonites (Fürsich, 1982).

Mineralogy.—?Calcitic (Carter, Barrera, & Tevesz, 1998). There are no conclusive studies on Liostrea mineralogy or shell microstructure. According to Carter, Barrera, and Tevesz (1998), the mineralogy of the different shell layers of members of family Ostreidae is calcitic.

Type species.—Ostrea blandina d'Orbigny, 1850, p. 375 (designated by Cox, 1964, p. 45).

Remarks.—Dimyodon Munier-Chalmas in Fischer, 1886 in 1880—1887, p. 937, is considered to be a junior synonym of Atreta (see discussion for Dimyodon, Genera not Included, p. 160). Although for a long time it was regarded as a plicatulid, both Fürsich and Werner (1988) and Hodges (1991), analyzing specimens of Atreta unguis (Loriol ex Merian, 1900) and Atreta intusstriata (Emmrich, 1853), respectively, demonstrated the presence of dimyarian structures typical of family Dimyidae.

Stratigraphic range.—Upper Triassic (Carnian)—Upper Cretaceous (Maastrichtian) (Bittner, 1895; Abdel-Gawad, 1986). Cox and others (1969) assigned it an Upper Triassic (Carnian)—Upper Cretaceous (Campanian) range. Sepkoski (2002) referred its origin to the Rhaetian, based on data provided by Skelton and Benton (1993). The oldest records of Atreta are from Carnian beds, with the species A. richthofeni (Bittner, 1895) and A. subrichthofeni (Krumbeck, 1924). H. Yin (1985) reported Dimyodon from Anisian and Ladinian beds. J. Chen, Stiller, and Komatsu (2006) believed that Anisian specimens of Dimyodon (D. qingyanensis Yin in Gan & Yin, 1978) were actually juvenile stages of Protostrea sinensis Hsu in Hsu & Chen, 1943 (type of Protostrea Chen, 1976). Atreta nilssoni (von Hagenow, 1842) is the latest species of the genus, reported from the Maastrichtian (Abdel-Gawad, 1986).

Paleogeographic distribution.—Tethys (Fig. 22). Over the study interval, this genus was only known from the Tethys domain, but in the upper Pliensbachian, it is recorded from Argentina (Damborenea, 2002a). Atreta showed dispersal patterns from the western Tethys to Eastern Circumpacific domain across the Hispanic corridor during the Early Jurassic (Damborenea, 2000).

Tethys domain; Late Triassic; Carnian of southern Alps (Bittner, 1895; F¨rsich & Wendt, 1977), Timor (Krumberck, 1924); Norian of Oman (Hautmann, 2001a); Norian—Rhaetian of Austria (Tanner, Lucas, & Chapman, 2004), Iran (Hautmann, 2001a, 2001b); Rhaetian of the Alps (Austria) (Tomašových, 2006a, 2006b), western Carpathians (Slovakia) (Tomašových, 2004), Austria and Germany (Hodges, 1991), England (Penarth Group) (Ivimey-Cook & others, 1999), Italy (Allasinaz, 1962); Early Jurassic; Hettangian of northwestern Europe (Hallam, 1987); early Liassic of South Wales (Hodges, 1991), Italy (Allasinaz, 1962).

Paleoautoecology.—B, E, S, C, Sed; C. Atreta was a cemented bivalve (fixed by its right valve) on other live invertebrates, such as sponges (Delvene, 2003; P. D. Taylor & Wilson, 2003), echinoids (Saint-Seine, 1951; Jagt, Neumann, & Schulp, 2007), other bivalves such as Plagiostoma, Gryphaea, Pinna, Antiquilima (Hodges, 1991), Indopecten (Hautmann, 2006a), Lopha, Cardinia, Myoconcha, and corals (Damborenea, 2002a). It is usually associated with other encrusting bivalves such as Liostrea (Hodges, 1991) or Lopha (Damborenea, 2002a). It was a gregarious bivalve, although it is rare to find it encrusting other individuals of the same species, and specimens are usually oriented with their dorsal part upward on sloping surfaces (Damborenea, 2002a).

Mineralogy.—Bimineralic (Malchus, 2000). Hodges (1991) did not find any shell preserved, and he believed it was likely that it was originally aragonitic. Malchus (2000) studied the microstructure of lower stages of excellently preserved Atreta specimens and found a foliated calcitic in outer shell layer and a well-developed cross-lamellar microstructure in the inner shell layer. Hautmann (2001a, 2006a) indicated that his specimens have a foliated calcite microstructure in the outer shell layer, and they did not have the inner one preserved. Outer shell layer: calcite (foliated). Inner shell layer: aragonite (cross-lamellar).

Type species.—Ostrea sinensis Hsu in Hsu & Chen, 1943, p. 136.

Remarks.—This genus was also called Proostrea (e.g., Skelton & Benton, 1993; Sepkoski, 2002) or Prostrea (e.g., Kobayashi & Tamura, 1983a) by mistake. Although its type species was originally included in Ostreoidea, following Morris in Skelton and Benton (1993), Komatsu, Akasaki, and others (2004), and J. Chen, Stiller, and Komatsu (2006), we include Protostrea in the Dimyidae (see J. Chen, Stiller, & Komatsu, 2006, for review and emendation of the genus). These authors interpreted Dimyodon qingyanensis Yin in Gan & Yin, 1978, as a juvenile stage of Protostrea sinensis and considered it the oldest member of the family Dimyidae.

Stratigraphic range.—Middle Triassic (Anisian) (J. Chen, Stiller, & Komatsu, 2006). Protostrea is a monospecific genus only known from the upper Anisian in the Qingyan formation (Stiller, 2000; Komatsu, Chen, & others, 2004; J. Chen, Stiller, & Komatsu, 2006).

Paleogeographic distribution.—Eastern Tethys (Fig. 22).

Tethys domain; Middle Triassic; Anisian of southern China (Guizhou province) (Stiller, 2000; Komatsu, Akasaki, & others, 2004; J. Chen, Stiller, & Komatsu, 2006).

Paleoautoecology.—B, E, S, C, Sed; C. Protostrea sinensis probably lived cemented to the substrate by their right valve by a large cementation area (J. Chen, Stiller, & Komatsu, 2006). Often it is found cemented to other shells and corals (Komatsu, Chen, & others, 2004). Protostrea was also a substrate for other organisms, such as crinoids (Stiller, 2000).

Mineralogy.—Bimineralic. Not much is known about the shell mineralogy and microstructure of members of the family Dimyidae. Waller (1978) indicated that they may have had an inner shell layer of aragonite and cross-lamellar microstructure and that they do not have a simple prismatic calcitic layer. J. Chen, Stiller, and Komatsu (2006, p. 160) studied thin sections of their specimens, which, although recrystallized into calcite, “… the shells originally probably had a mainly crossed-lamellar microstructure (originally aragonitic); in parts (at least of right valves) there are relics of (an) irregular simple-prismatic outer layer (s) (originally calcitic).”

Type species.—Harpax parkinsoni Bronn, 1824, p. 52.

Remarks.—Although Harpax was considered a junior synonym of Plicatula Lamarck, 1801, by Cox and others (1969), some authors still regarded it as a valid subgenus of Plicatula (Okuneva, 1985; Damborenea, 1993; Aberhan, 1994a, 1998a; Gahr, 2002, among others). Recently, Damborenea (2002a) validated the genus, distinguishing it from Plicatula due to its hinge details, relative convexity of the valves, ornamentation, and ligament (see discussion in Damborenea, 2002a, p. 86–89). The hinge of many species attributed to Plicatula is unknown, and so species undoubtedly included in Harpax are: Harpax parkinsoni Bronn, 1824, Harpax rapa (Bayle & Coquand, 1851), Harpax kolymica (Polubotko in Kiparisova, Bychkov, & Polubotko, 1966), Harpax simplex Milova, 1976, Harpax spinosa (J. Sowerby, 1819), and Harpax auricula (Eudes-Deslongchamps, 1860), among others.

Stratigraphic range.—Upper Triassic (Norian)—Lower Jurassic (Toarcian) (Damborenea, 1993; Gahr, 2002). It is difficult to assign a specific range to this genus, since diagnostic characters (for example, the hinge) of many species are not known (Damborenea, 2002a). The oldest solid records are from the Norian (Okuneva, 1985; Damborenea, 1993), with the youngest being from the lower Toarcian of Spain and Portugal (Gahr, 2002). Hautmann (2001a, 2001b) considered the genus to be only present in the Lower Jurassic.

Paleogeographic distribution.—Boreal and Austral, ?Tethys (Fig. 23). Harpax had a bipolar distribution, at least during the Early Jurassic (Damborenea, 1993, 1996a, 2001). It originated in the Boreal domain during the Late Triassic. Later, during the Pliensbachian—Toarcian, it was also reported from the Tethys domain (Gahr, 2002). With some doubt, it was also reported from the Rhaetian—Hettangian boundary in Tibet (J. Yin & McRoberts, 2006) and from Sinemurian beds of Morocco (Tomašových, 2006c).

Boreal domain: Late Triassic: Norian of Siberia (Okuneva, 1985), northeastern Asia (Polubotko & Repin, 1990); Norian—Rhaetian of Siberia (Kiparisova, Bychkov, & Polubotko, 1966; Polubotko, 1968a; Bychkov & others, 1976); Early Jurassic: northeastern Russia (Milova, 1976); Hettangian of northeastern Asia (Polubotko & Repin, 1990); Hettangian—Sinemurian of Canada (Aberhan, 1998a; Aberhan, Hrudka, & Poulton, 1998).

Austral domain: Early Jurassic: Argentina (Damborenea, 1993, 2002a, 2002b); Hettangian—Sinemurian of Chile and Argentina (Damborenea, 1996a), ?New Zealand (Damborenea, 1993); Sinemurian of Chile (Aberhan, 1994a).

Paleoautoecology.—B, E, S, C, Sed; C. The distribution of bipolar (or antitropical) organisms is determined by temperature and substrate availability (Sha, 1996). They are abundant in shallow water areas at high latitudes and in deep water areas at low-latitude seas (Sha & Fürsich, 1994). According to several studies (see Damborenea, 2002a, p. 93), juvenile stages of Harpax were often cemented by the right valve to hard substrates (other shells, pebbles, rocks). However, in adult stages, they were often found loose in the sediment, so they had a free mode of life (Damborenea, 2002a). Sha (1996), based on various characters, such as the presence of byssal notch and sinus and pseudoctenolium, believed that in its juvenile stages, it also remained byssate, and he suggested that perhaps it had a pseudoplanktonic mode of life, attaching to floating objects (e.g., wood) or other swimming or nektonic organisms.

Mineralogy.—Bimineralic (Carter, 1990a, p. 226; Carter, Barrera, & Tevesz, 1998, p. 1003). Outer shell layer: calcite (foliated). Middle shell layer: calcite. Inner shell layer: aragonite.

Type species.—Plicatula imago Bittner, 1895, p. 213.

Stratigraphic range.—Upper Triassic (Carnian—Rhaetian) (Bittner, 1895; Hautmann, 2001a, 2001b). Carter (1990a) proposed Eoplicatula as a subgenus of Plicatula and only included the type species from the Carnian of Italy. Subsequently, Hautmann (2001a) included the species Plicatula difficilis Healey, 1908, from Rhaetian beds of Burma and Eoplicatula parvadehensis Hautmann, 2001a, from the Norian of Iran. Hautmann and others (2005) reported Eoplicatula from Rhaetian beds of southern Tibet but did not figure or describe the specimens.

Paleogeographic distribution.—Tethys (Fig. 23).

Tethys domain: Late Triassic: Carnian of Italy (Bittner, 1895; Leonardi, 1943; Carter, 1990a); Norian of Iran (Hautmann, 2001a, 2001b; Fürsich & Hautmann, 2005); Rhaetian of Burma (Healey, 1908).

Paleoautoecology.—B, E, S, C, Sed; C. Eoplicatula cemented to the substrate by its right valve. According to Hautmann (2001b), it was a reef-builder organism.

Mineralogy.—Bimineralic (Carter, 1990a, p. 223; Hautmann, 2001b). Outer shell layer: calcite (prismatic-foliated). Middle shell layer: aragonite (cross-lamellar). Inner shell layer: aragonite (prismatic—cross-lamellar).

Type species.—Pseudoplacunopsis affixa Bittner, 1895, p. 215.

Remarks.—After Todd and Palmer (2002), who proposed that Placunopsis Morris & Lycett, 1853 in 1851–1855, p. 5, is a genus belonging to the Jurassic family Anomiidae, several species that were traditionally attributed to this genus were rejected, as they did not have a byssal foramen, and they were regarded as terquemids (=prospondylids) instead. While Hölder (1990) considered species from Triassic and Cretaceous ages to be within Placunopsis, Todd and Palmer (2002) proposed that their affinities are uncertain, and their knowledge is based on new well-preserved materials. We believe that many of the Triassic species referred to Placunopsis and included into the family Terquemiidae Cox, 1964, among them the so-called false oyster, are, in fact, true plicatulids and should be referred to Pseudoplacunopsis. Checa and others (2003) resampled the Middle Triassic (Ladinian) localities studied by Schmidt (1935) and Márquez-Aliaga, Hirsch, and López-Garrido (1986) from the Betic ranges (Jaen), and they obtained several thousand specimens of Placunopsis flabellum Schmidt, 1935, in which only the calcite microstructure of the right valves (the cemented ones) was preserved. In tens of specimens, details of the hinge could be observed, showing an elongated ligament furrow bordered by two crura diverging from the beak and pits corresponding to the other valve crura and inserted below the hinge line. The external ornamentation presented antimarginal thick ribs, and thus the species was referred to Enantiostreon; but hinge characters indicate that P. flabellum was a true plicatulid. Subsequently, one of the authors (Márquez-Aliaga) found identical hinge characters in specimens from Ladinian beds of the Iberian range (Cuenca) attributed to Placunopsis teruelensis Wurm, 1911. This species is ornamented by fine ribs. There are many Middle Triassic nominal species assigned to this genus, which could, in fact, be regarded as synonyms due to the variability of the cemented valve. Among the finely ornamented species, P. plana (Giebel, 1856) from the Germanic Muschelkalk could include as synonyms the following names: alpina Winkler, 1859, schaflautli Winkler, 1859, teruelensis Wurm, 1911, and filicostata Hölder, 1990. Within the heavily ornamented species, matercula Quenstedt, 1852 in 1851–1852, could include as a synonym flabellmn Schmidt (Checa & others, 2003). Recently, Posenato (2008b) developed similar ideas.

Stratigraphic range.—Middle Triassic (Anisian)—Upper Triassic (Rhaetian) (Posenato, 2008b; Márquez-Aliaga, Damborenea, & Goy, 2008a). Cox and others (1969) assigned it an Upper Triassic range, and Hautmann (2001a) also considered that it ranged from the Carnian, but new records, as discussed above, confirmed its presence in Middle Triassic deposits. Regarding the upper extension of its stratigraphic range, Hautmann (2001a) considered that Pseudoplacunopsis lived until Kimmeridgian times, represented by the species Plicatula ogerieni Loriol, 1904. Hautmann (2001a) did not make any comments about this species, nor did we find any record of the genus for the Jurassic; and its last appearance seems to be Rhaetian. It is interesting to note that most references to this genus are based on the diagnosis given by Bittner (1895) and Cox (1924), and not on the emended one by Hautmann (2001a), as the hinge and the ligament area are rarely preserved in specimens attributed to this genus.

Paleogeographic distribution.—Tethys and Circumpacific (Fig. 23).

Tethys domain: Middle Triassic: Anisian of Italy (Posenato, 2008b); Ladinian of Spain (Schmidt, 1935; Márquez-Aliaga, 1985; Martínez & Márquez-Aliaga, 1992; López-Gómez & others, 1994; Márquez-Aliaga & Ros, 2002; Márquez-Aliaga, Budurov, & Martínez, 1996; Márquez-Aliaga & others, 2004), Germany (Hagdorn & Simon, 1983; Hölder, 1990), France (Brocard & Philip, 1989), Israel (Lerman, 1960), Poland (Assmann, 1916), Italy (Posenato, 2002), Jordan (Cox, 1924); Late Triassic: Carnian of Spain (Martín-Algarra, Solé de Porta, & Márquez-Aliaga, 1995), Italy (Bittner, 1895; Leonardi, 1943); Norian—Rhaetian of Iran (Hautmann, 2001b); Rhaetian of Austria (Posenato, 2008b), Spain (Márquez-Aliaga, Damborenea, & Goy, 2008b; Márquez-Aliaga & others, 2010).

Circumpacific domain: Middle Triassic: Ladinian of Nevada (United States) (Waller in Waller & Stanley, 2005).

Paleoautoecology.—B, E, S, C, Sed; C. Pseudoplacunopsis was a cementing bivalve. It attached to the substrate by its right valve, and according to Hautmann (2001a), it was a reef builder. Márquez-Aliaga and Martínez (1994) studied its behavior as an epizoan organism.

Mineralogy.—Bimineralic (De Renzi & Márquez-Aliaga, 1980; Márquez-Aliaga & Márquez, 2000). Outer shell layer: calcite (foliated). Inner shell layer: aragonite (cross-lamellar).

Type species.—Posidonomya clarae Hauer, 1850, p. 112.

Remarks.—Several taxa related to Claraia will not be considered in this analysis for various reasons: either they are regarded as synonyms of Claraia or their separation at generic level is not justified. These taxa are: Pseudoclaraia Zhang, 1980, p. 438, 443, Pteroclaraia Guo, 1985, p. 150, 265, Guichiella J. Li & Ding, 1981, p. 328–329, Claraioides Z. Fang, 1993, p. 653, 660, Epiclaraia Gavrilova, 1995, p. 156, and Rugiclaraia Waterhouse, 2000, p. 179 (see discussion for each of them in Genera not Included, p. 156).

Stratigraphic range.—upper Permian (Wuchiapingian)—Lower Triassic (middle Olenekian) (F. Yang, Peng, & Gao, 2001; McRoberts, 2010). For a long time, Claraia was regarded as a Lower Triassic index fossil. Cox and others (1969) assigned it a Lower Triassic range with a cosmopolitan distribution. Later, Nakazawa and others (1975) reported Claraia bioni Nakazawa in Nakazawa & others, 1975, from upper Permian sediments. Since then, there were many new upper Permian records (H. Yin, 1983; F. Yang, Peng, & Gao, 2001; Z. Fang, 1993, 2003; Gao, Yang, & Peng, 2004; Kotlyar, Zakharov, & Polubotko, 2004; He, Feng, & others, 2007; He, Shi, & others, 2007). Boyd and Newell (1979) reported Claraia? posidoniformis Termier & Termier, 1977, from Tunisian Guadalupian beds, but they doubted the generic relations of this species, because it shows some features that are not typical of Claraia.

Paleogeographic distribution.—Cosmopolitan (Fig. 24). During the late Permian, Claraia was widely distributed, mainly in the eastern part of Tethys. During the Early Triassic, it was abundant almost everywhere that beds of this age occur. For this reason, even though it was not reported from certain areas, a cosmopolitan distribution is given.

Tethys domain: late Permian: Kashmir (India) (Nakazawa & others, 1975); Wuchiapingian of China (F. Yang, Peng, & Gao, 2001); Changhsingian of China (Z. Zhang, 1980; H. Yin, 1983, 1990; Z. Fang, 1993, 2003; F. Yang, Peng, & Gao, 2001; Gao, Yang, & Peng, 2004; Z. Chen, Kaiho, & others, 2006; He, Feng, & others, 2007; He, Shi, & others, 2007), northwestern Caucasus (Russia) (Kotlyar, Zakharov, & Polubotko, 2004; Ruban, 2006a); Early Triassic: Pamir (Afghanistan) (Polubotko, Payevskaya, & Repin, 2001), Himalayas (Nepal) (Waterhouse, 2000), Italy (Leonardi, 1935; Broglio-Loriga, Masetti, & Neri, 1982; Neri, Pasini, & Posenato, 1986; Broglio-Loriga & others, 1988, 1990; Posenato, 1988; Posenato, Sciunnach, & Garzanti, 1996; Fraiser & Bottjer, 2007a, 2007b), China (Hsu, 1936–1937; F. Wu, 1985; Z. Li & others, 1986; Lu & Chen, 1986; S. Yang, Wang, & Hao, 1986; Z. Yang & others, 1987; Ling, 1988; M. Wang, 1993; Tong & Yin, 2002), Ussuriland (Russia) (Kiparisova, 1938); Induan of China (C. Chen, 1982; F. Yang, Peng, & Gao, 2001; He, Feng, & others, 2007), Italy (Leonardi, 1960), Malaysia (Ichikawa & Yin, 1966; Tamura & others, 1975), Vietnam (Vu Khuc & Huyen, 1998), Alberta (Canada) (Newell & Boyd, 1995; McRoberts, 2010); Olenekian of Mangyshlak (Kazakhstan) (Gavrilova, 1995), China (H. Yin, 1990; J. Chen & Komatsu, 2002), Pakistan (Nakazawa, 1996), Vietnam (Komatsu & Huyen, 2006).

Circumpacific domain: Early Triassic: Wyoming and Idaho (United States) (Newell & Kummel, 1942), Alberta (Canada) (Newell & Boyd, 1970), Japan (Nakazawa, 1971; Hayami, 1975); Induan of Nevada (United States) (Ciriacks, 1963; Schubert, 1993; Newell & Boyd, 1995; Schubert & Bottjer, 1995; Boyer, Bottjer, & Droser, 2004; Fraiser & Bottjer, 2007a, 2007b).

Boreal domain: late Permian: eastern Greenland (Newell & Boyd, 1995), Nova Zemla (Arctic Ocean) (Muromtseva, 1984); Early Triassic: Queen Elizabeth Islands (Arctic Archipelago, Canada) (Tozer, 1961, 1962, 1970).

Paleoautoecology.—B-Ps, E, S, Epi, Se-FaM. Several modes of life have been attributed to Claraia, ranging from benthic epibyssate (Z. Fang, 1993; F. Yang, Peng, & Gao, 2001) to pseudoplanktonic and even occasional swimmer (F. Yang, Peng, & Gao, 2001). Claraia shell morphology subtly changed through time. These differences are primarily related to the morphology of the byssal notch, the ornamentation, and the shape of the auricles (F. Yang, Peng, & Gao, 2001; He, Feng, & others, 2007). Permian forms had a more developed and deep byssal notch, shells were small in size, thin, and slightly inequivalve; they were interpreted as living epibyssate with the capacity to swim occasionally (F. Yang, Peng, & Gao, 2001). However, due to the associated fauna, e.g., ammonoids, they were also interpreted as pseudoplanktonic (H. Yin, 1983). Nevertheless, according to F. Yang, Peng, and Gao (2001), features present in Permian forms were unsuited to this mode of life. On the other hand, in the Triassic forms, the byssal notch was shallower, which is associated with increased mobility (Z. Fang, 1993; see also He, Feng, & others, 2007, table 1), and the shells were less ornamented (F. Yang, Peng, & Gao, 2001). These forms were also interpreted by F. Yang, Peng, and Gao (2001) as being pseudoplanktonic bivalves that attached themselves to pieces of wood or algae.

The genus occurred primarily in deep-water Permian deposits, but, by the Triassic, it was in all types of environments, from shallow to deep (F. Yang, Peng, & Gao, 2001). This fact was related to an opportunistic behavior during recovery from the Permian—Triassic (P/T) extinction event (Schubert & Bottjer, 1995; Rodland & Bottjer, 2001). This success during the Triassic appears to be related to the morphological change, since Permian forms with a deep byssal notch did not survive the P/T event; however, the forms with a shallower byssal notch diversified enormously [from 3 species in late Permian to over 30 in the Triassic (He, Feng, & others, 2007)]. According to F. Yang, Peng, and Gao (2001), this was also related to the mode of life of Claraia larvae, which probably had a veliger planktonic stage. The deep-water habitats in which mostly Permian forms were found were interpreted by Gao, Yang, and Peng (2004) as potential refuges for those forms that survived and reached the Early Triassic. It is hard to assign a unique mode of life to all species of Claraia, since they have a wide range of morphological features that suggests that some species could have been epibenthic, pseudoplanktonic, and even occasional swimmers (He, Feng, & others, 2007).

Mineralogy.—Bimineralic (Boyd & Newell, 1976; Newell & Boyd, 1985, 1995; Carter, 1990a, 1990b). Outer shell layer: calcite (prismatic). Inner shell layer: aragonite (?).

Type species.—Pseudomonotis telleri Bittner, 1898, p. 710.

Stratigraphic range.—Lower Triassic (Induan—Olenekian) (Broglio-Loriga & Mirabella, 1986). Cox and others (1969) assigned it a Lower Triassic—Upper Triassic range. However, Broglio-Loriga and Mirabella (1986) did a comprehensive study on Eumorphotis, and they noted that Middle and Upper Triassic forms were highly dubious, and therefore they restricted the range of Eumorphotis to the Lower Triassic. Newell and Boyd (1995) assigned it the same range. Furthermore, these authors argued that Heteropecten Kegel & Costa, 1951, and Eumorphotis were virtually indistinguishable and that the reason for proposing Eumorphotis was more to separate the Paleozoic from the Triassic forms than to recognize significant morphological differences between the two groups. In fact, Newell and Boyd (1995) considered that some specimens attributed by Bittner (1901b) to the Triassic Eumorphotis from eastern Siberia are similar to Heteropecten. Moreover, Eumorphotis was also reported from the upper Permian, but Broglio-Loriga and Mirabella (1986) doubted all these records, because they were based on poorly preserved material. Posenato, Pelikán, and Hips (2005) proposed a new species, Eumorphotis lorigae Posenato, Pelikán, & Hips, 2005, and they referred it to the upper Permian (upper Changhsingian), but, as indicated by the authors, this age is only provisionally based on bivalves and brachiopods, and thus we will not take this record into account until new data allow a more precise age determination.