Introduction

Brodiechelys brodiei (Lydekker, 1889) is a eucryptodiran turtle currently known only from the Wealden of the United Kingdom. Available information on this taxon was, until now, very limited. However, ten shells from the type locality of Brighstone Bay (Isle of Wight, Wessex Sub-basin) were recently attributed to it (Pérez-García 2012a). Brodiechelys is also present in the area of Hastings (Sussex, Weald Sub-basin), where fragmentary and poorly preserved shells, corresponding to an indeterminate species, have also been identified. Study of these specimens of Brodiechelys brodiei indicated its intraspecific variability, and the identification of Plesiochelys valdensis Lydekker, 1889 and Plesiochelys vectensis Hooley, 1900 as junior synonyms of Brodiechelys brodiei. The comparison of these shells has led a new diagnosis for this taxon and evidence that it is a member of the stem group of Cryptodira (Pérez-García 2012a).

The Spanish Iberian Range records the highest European diversity of Early Cretaceous continental turtles, particularly in the Hauterivian-Aptian interval (Pérez-García and Murelaga 2012a). Members of Pan-Pleurodira (Dortokidae), stem Testudines (at least two solemydid taxa), Paracryptodira (Pleurosternidae), several lineages of crown cryptodires, but also unnamed stem cryptodires, have been identified there (Pérez-García et al. 2011). Stem cryptodires from Igea (La Rioja, eastern Cameros Basin) and Morella (Castellón, Morella Sub-basin, Maestrazgo Basin) cannot be assigned to any of the taxa so far identified on the Iberian Peninsula (Pérez-García et al. 2010). Some of these specimens have been identified as one or more taxa related to the British taxon Brodiechelys brodiei, but the assignment was preliminary because of limited knowledge of the variability of this taxon (Pérez-García et al. 2011).

The recent review of Brodiechelys brodiei (Pérez-García 2012a) allows us to study the related Spanish material. We analyze here the specimens from the Morella Sub-basin (Fig. 1), and these are identified as belonging to a new species closely related to Brodiechelys brodiei and are therefore assigned to the genus Brodiechelys. Several characters that cannot be scored for the British material help to improve knowledge of this clade of turtles. The proposal of a newspecies of Brodiechelys means the diagnosis for this until now monospecific genus, as well as its two species, are revised. This new material provides valuable information on the palaeobiogeographic relationships of the Early Cretaceous European turtles.

Institutional abbreviations.—CMP, Collection of the Mas de la Parreta Quarry, housed in the Valltorta Museum, Tirig, Castellón, Spain; IWCMS, Isle of Wight County Museum, Sandown, UK; NHMUK, Natural History Museum, London, UK.

Systematic palaeontology

Fig. 1.

Geographical location of Morella (Castellón, Spain), the type localityity of Brodiechelys royoi.

Fig. 2.

Type specimens of Brodiechelys royoi sp. nov. from Morella (Castellón, Spain). A. CMP-3b/181, holotype, shell in dorsal (A₁, A2) and ventral (A₃, A₄) views. B. CMP-3c/293, second right costal plate in dorsal (B₁, B₂) and ventral (B₃, B₄) views. C. CMP-3c/122, first right costal in dorsal (C₁, C₂) and ventral (C₃, C₄) views.

Discussion

Phylogenese analyses.—To establish the phylogenetic position of the new Spanish taxon, two cladistic analyses were conducted. For the first, we used the modified version of the data matrix of Sterli and de la Fuente (2011) proposed by Pérez-García and Murelaga (2012b), in which all representatives of Pan-Pleurodira are excluded and several Asian and European eucryptodires are included {Chengyuchelys baenoides Young and Chow, 1953, Tholemys passmorei Andrews, 1921, Plesiochelys planiceps [Owen, 1842], Brodiechelys brodiei, Hylaeochelys belli [Mante11, 1844], Chitracephalus dumonii Dollo, 1885, and the Spanish Larachelus morla Pérez-García and Murelaga, 2012b; see Appendix 1). Moreover, another two taxa currently proposed as members of Xinjiangchelyidae (sensu Tong et al. 2012), are also included (using the character encoding proposed by Tong et al. 2011): Protoxinjiangehelys salis Tong, Danilov, Ye, Ouyang, and Peng, 2011 and Xinjiangchelys tianshanensis Nessov, 1995. The modifications in the processing of certain characters in Pleurosternon bullockii (Owen, 1842), Dinoehelys whitei Gaffney, 1979, and Glyptops plicatulus Marsh, 1890 proposed by Pérez-García and Ortega (2011), and in Peltoehelys duehastelii Dollo, 1885 proposed by Pérez-García (2011) have been included. The modification in the coding of character 82 (costal B) in Xinjiangchelys latimarginalis (Young and Chow, 1953) sensu Peng and Brinkman (1993) proposed by Tong et al. (2012) has been included.

The second phylogenetic analysis was conducted using the data matrix proposed by Tong et al. (2012). In addition to the inclusion of the new taxon, Brodiechelys brodiei and Larachelus morla are also incorporated (see Appendix 1).

The phylogenetic analyses were conducted using TNT v. 1.0 (Goloboff et al. 2008), with Sphenodon punctatus (Gray, 1842) as the outgroup for the first, and Kayentachelys aprix Gaffney, Hutchison, Jenkins, and Meeker, 1987 for the second. All characters were considered unordered and equally weighted.

Results and systematic implications.—The first phylogenetic analysis resulted in 94 most parsimonious trees of 420 steps (CI = 0.469, RI = 0.841) (Fig. 3A). The resulting majority rule tree topology basically coincides with that proposed by Pérez-García and Murelaga (2012b). Santanachelys gaffneyi Hirayama, 1998 and Solnhofia parsonsi Gaffney, 1975 are obtained as the two most basal taxa of Pan-Cry ptodira. All other members of Pan-Cryptodira are grouped into two lineages in all trees obtained. The Asian Siamochelys peninsularis Tong, Buffetaut, and Suteethorn, 2002, Chengyuchelys baenoides, Protoxinjiangchelys salis, Xinjiangchelys tianshanensis, Xinjiangchelys latimarginalis, and the European Brodiechelys brodiei, the new taxon from Morella, and the taxon from Salas de los Infantes (i.e., Larachelus morla) are obtained as members of the stem group of Cryptodira. This analysis could not establish the precise phylogenetic relationships among these taxa owing to limited information on several of them, in most cases including only characters of the shell. In fact, putative members of the same genus (e.g., Xinjiangchelys tianshanensis and X. latimarginalis) are not grouped in this analysis. The monophyletic group within Pan-Cryptodira comprising stem and crown-group Cryptodira is diagnosed by two synapomorphies: vertebrals II–IV as narrow as or narrower than pleurals (character 87); length of first dorsal rib intermediate to short, extends less than half-way across first costal (character 113). The European representatives of the stem group of Cryptodira and the Asian taxon Xinjiangchelys latimarginalis form a monophyletic group, diagnosed by the presence of a medial contact of the posterior costals (character 82). The node grouping Brodiechelys brodiei and Brodiechelys royoi is diagnosed by the presence of an osseous connection between the carapace and the plastron (character 89).

Fig. 3.

Phylogenetic hypotheses of the new taxon Brodiechelys royoi based on the modified data set of Sterli and de la Fuente (2011) proposed here (A), and on the data matrix proposed by Tong et al. (2012) (B). Values refer percentages under 100% obtained in the majority rule analyses.

The node that groups species of Brodiechelys with Xinjiangchelys latimarginalis is consistent with the hypothesis proposed by some authors that Brodiechelys brodiei belongs to the clade of freshwater turtles Xinjiangchelyidae, whose presence has been confirmed exclusively in the Middle Jurassic to Early Cretaceous of Asia (Hirayama et al. 2000; Tong et al. 2012). Information on many xinjiangchelyids is limited, so making it difficult to establish their relationships, and indeed the monophyly of this group has been questioned (Rabi et al. 2010). Recently, Tong et al. (2011) performed a global phylogenetic analysis, based on a modified version of the phylogenetic proposal of Joyce (2007), and this indicated a node of Testudines grouping Bashuchelys sp. (Tong et al. 2011) and Chuannanchelys dashanpuensis (Fang, 1987), taxa identified there as members of Bashuchelyidae, and this clade was identified as the sister group of Protoxinjiangehelys salis. The lineage grouping these three taxa was part of a polytomy with Xinjiangchelys latimarginalis and X. tianshanensis. Therefore, Xinjiangchelyidae in the traditional sense and Bashuchelyidae can therefore not be recognized as two non-overlapping monophyletic clades in that analysis. The global phylogenetic analysis performed by Anquetin (2012), also based on the matrix of Joyce (2007), generated a poorly supported clade identified as Xinjiangchelyidae, comprising Siamochelys peninsularis, Xinjiangchelys qiguensis Matzke, Maisch, Sun, Pfretzschner, and Stöhr, 2004, X. tianshanensis, X. latimarginalis, and Annemys levensis Sukhanov and Narmandakh, 2006 (taxon reassigned to Xinjiangchelys levensis by Tong et al. 2012). In order to better understand the relationships among the members of Bashuchelyidae and Xinjiangchelyidae, Tong et al. (2012) proposed a new data matrix with only 24 characters, all of them referring to the shell, and with Kay entache lys aprix as outgroup. They found a monophyletic Bashuchelyidae, comprising only the species Bashuchelys youngi Tong, Danilov, Ye, Ouyang, and Peng 2011 and Bashuchelys zigongensis (Ye, 1982), and this was the sister group of the node grouping Chuannanchelys dashanpuensis and Xinjiangchelyidae. In addition to the members of Protoxinjiangchelys Tong, Danilov, Ye, Ouyang, and Peng, 2011, Chengyuchelys Young and Chow, 1953, Tienfuchelys Young and Chow, 1953, and Xinjiangchelys Ye, 1986. Tong et al. (2012) considered that Xinjiangchelyidae also contained another Asian taxon, Yanduchelys Peng, Ye, Gao, Shu, and Jiang 2005, and the European Brodiechelys, neither of them included in the analysis.

The new Brodiechelys royoi allows characterization of some previously unknown characters of this genus (Pérez-García 2012a), which are shared with the Asian members of Xinjiangchelyidae: the first dorsal rib is short and both the axillary and inguinal buttresses contact exclusively with the peripheral series.

Tong et al. (2012) proposed anew diagnosis for Xinjiangchelyidae. Brodiechelys brodiei and Brodi eche lys royoi share with the exclusive combination of characters of Xinjiangchelyidae: shell height moderate to low domed (their character 1); first thoracic rib reduced (character 2); two or three suprapygals, being the last two suprapygals of similar width or the last one slightly wider (character 3); seventh to eleventh peripherals transversely expanded (character 5); pectoral and abdominal scutes similar in length or pectoral slightly longer (character 11); femoro-anal sulcus usually omega-shaped, reaching or extending onto the hypoplastron (character 12); three or four pairs of inframarginals (character 13). The node Brodiechelys, or at least one of its representatives, shows autapomorphies in other characters of the cited diagnosis. B. royoi has anterior peripherals with prominent guttered edges (character 4). However, B. brodiei does not share this character state. The members of Brodiechelys share with the Asian representatives of Xinjiangchelyidae the overlapping of some marginals on the lateral region of the costal plates (character 6). Nevertheless, the number of marginals that overlap the costals is lower than in the Asian taxa, being the fifth to seventh marginals in B. brodiei but only the fifth in B. royoi. The relationship between the size of the entoplastron and that of the epiplastra can be highly variable in the representatives of Brodiechelys, these two plates not always being similar in size (character 8). It is very different, for example, in the specimen of B. brodiei NHMUK R11173 (see Pérez-García 2012a: figs. 3F and 4F). Although in some Brodiechelys specimens, the entoplastron is quite large, in others it is very small (e.g., NHMUK R11173). Although this plate is longer than wide or as long as wide in some specimens, it also can be wider than long (e.g., NHMUK R6683; Pérez-García 2012a: figs. 3J and 4J) (character 9). The posterior sulcus of gulars and extragulars of Brodiechelys is not a straight line, and the pair of gulars is slightly (e.g., NHMUK R11146; Pérez-García 2012a: figs. 3K and 4K) or significantly (e.g., NHMUK R11174; Pérez-García 2012a: figs. 3G and 4G) overlapped onto the entoplastron (character 10). The midline sulcus of the plastron of some specimens is sinuous (character 14), but it is very little or not sinuous in others. It is slightly sinuous in some specimens of B. brodiei (e.g., NHMUK R6683, NHMUK R11146, and NHMUK R11147), but not in others (e.g., NHMUK R11173, NHMUK R11174). The presence of dorsal processes of the epiplastra (character 7) and musk ducts (character 15) has not been, until now, reported in this taxon.

The known material of Larachelus morla (see Pérez-García and Murelaga 2012b) also supports its assignment to Xinjiangchelyidae. However, it differs from the other members of this group in the presence of a single suprapygal plate, and in that, as in the case of the representatives of Brodiechelys, the pair of gular scutes is superimposed on the antero-medial region of the entoplastron.

We obtain three most parsimonious trees of 49 steps (CI = 0.531, RI = 0.803) as result of the inclusion of Larachelus morla, Brodiechelys brodie, and Brodiechelys royoi in the data matrix of Tong et al. (2012) (Fig. 3B). The resulting majority rule tree basically coincides with that proposed by Tong et al. 2012. The clade that groups Chuannanchelys dashanpuensis and the members of Xinjiangchelyidae is characterized by the following synapomorphies: epiplastra with long midline contact (character 12 of the data matrix proposed by Tong et al. 2012); posterolateral process of epiplastron (character 13); weak or absent overlapping of entoplastron by intergulars (character 16); diamond shape of the entoplastron (character 23). The Xinjiangchelyidae share the absence of mesoplastra (character 15). The node grouping the Xinjiangehelys species and the three European taxa is diagnosed by: absence of overlapping of the tenth peripheral by the fifth vertebral (character 10); ligamentous plastron/ carapace connection (character 11); oval shape of the entoplastron (character 23). The three European taxa are grouped by the presence of: strong overlapping of entoplastron by intergulars (character 16); middle part of the humeropectoral sulcus anterior to the base of the anterior lobe (character 17); diamond shape of the entoplastron (character 23). Brodiechelys brodiei and Brodiechelys royoi share a sutural plastron/ carapace connection (character 11). Brodiechelys brodiei presents an autapomorphy in this analysis: straight sulcus between the third and fourth vertebrals (character 7).

Palaeobiogeographic implications.—The recent studies of Brodiechelys brodiei (Pérez-García 2012a) and some Spanish material (Pérez-García and Murelaga 2012b) support the presence of Xinjiangchelyidae outside Asia (Hirayama et al. 2000; Tong et al. 2012), and this is confirmed here with the new Spanish taxon.

Studies of Iberian Early Cretaceous sites, especially in the Arcillas de Morella Formation (Maestrazgo Basin), have revealed numerous terrestrial and freshwater reptile taxa with clear similarities with Hauterivian to Aptian Wealden facies from northwest Europe (Canudo el at. 1996; Escaso et al. 2005; Torcida Fernández-Baldor 2006; Pereda-Suberbiola et al. 2007; Sánchez-Hernández et al. 2007; Buscalioni et al. 2008; Gasulla et al. 2009, 2011; Mateus et al. 2011). Holtz et al. (2004) proposed that the Greater Wealden, comprising localities of the Lower Cretaceous of England and continental Europe, as well as comparable faunas of southern and central Europe, western North America, and Africa, share a common composition of dinosaur faunas. In general, the Iberian Wealden faunas share most of their members with localities of the Wealden Supergroup and its equivalents in Belgium, England, France and Germany (Naish and Martill 2001; Weishampel et al. 2004). Some areas in southern England (Wessex Sub-basin of the Isle of Wight and Dorset, Weald Clay of West Sussex and Surrey) and Belgium (Bernissart, in the Mons Basin) seem to have the greatest similarity with the Arcillas de Morella Formation, especially in its dinosaur and crocodile faunas (Gasulla et al. 2009, 2011).

Several freshwater and terrestrial turtles from the Iberian Hauterivian—Aptian interval are shared or are closely related to taxa from the European Wealden areas.

The two aquatic turtles from Bernissart include one, Peltochelys duchastelii, that is unique to that locality, and Chitracephalus dumonii, which has recently been identified in Spain (Pérez-García 2012b). This taxon is present in both the eastern Cameros Basin (Hauterivian—Barremian of Tenadas del Jabalí, Pinilla de los Moros Formation, Urbion Group) and in the western Cameros Basin (Barremian—Aptian of Torremuña, Enciso Group).

The English and Spanish records of turtles share members of Solemydidae (stem Testudines). A form closely related to the British taxon Helochelydra nopcsai, from the Wessex Formation of the Isle of Wight, is identified in Morella and in two locations of the Cameros Basin (Barbadillo del Mercado and Cabezón de la Sierra, Pantano de la Cuerda del Pozo Formation/Castrillo de la Reina Formation, Urbión Group) (Pérez-García et al. 2011). A second member of Solemydidae is identified in the Early Cretaceous (Aptian and Albian) of Gargallo and Cabezo de las Eras (Teruel, Maestrazgo Basin). It could be closely related to the British Plastremys, from the Upper Greensand of the Isle of Wight (Albian—?earliest Cenomanian) and in the Cambridge Greensand (Albian) of Cambridge (Joyce et al. 2011; Pérez-García et al. 2011). Solemydidae is interpreted as a terrestrial group of turtles (Lapparent de Broin and Murelaga 1999; Scheyer et al. 2012).

No Early Cretaceous freshwater turtle genus shared between United Kingdom and the Iberian Peninsula had been so far identified. How ever, the freshwater Brodiechelys, from the Vectis Formation of the Isle of Wight (Barremian—early Aptian, Wealden Group, Wessex Sub-basin, Wessex-Weald Basin), and recognized in the Hasting Group of Hastings (Sussex) (Berriasian—Valanginian of the Weald Sub-basin, Wessex-Weald Basin), is identified herein for the Iberian record (Early Aptian of the Morella Sub-basin).

The monophyly of Xinjiangchelyidae (Anquetin 2012; Tong et al. 2012) is supported, and the presence of Xinjiangchelyidae outside Asia is confirmed here. The European taxa Brodiechelys brodiei, B. royoi, and Larachelus morla are attributed to this clade. In addition, some poorly known European Early Cretaceous taxa, as well as new forms, have recently identified another freshwater clade also present in the synchronous Asian record. So, Chitracephalus dumonii and the recently described Hoyasemys jimenezi (Upper Barremian of Las Hoyas, Cuenca, Spain) and Galvechelone lopezmartinezae (Lower Barremian of Galve, Teruel, Spain), have been attributed to the clade comprising members of “Macrobaenidae” and “Sinemydidae” (Pérez-García et al. 2012; Pérez-García 2012b; Pérez-García and Murelaga 2012a).

Conclusions

Brodiechelys was a hitherto poorly known European taxon based on scarce material. New materials from the Early Cretaceous of the Iberian Range (Spain) indicate the presence of Brodiechelys outside the United Kingdom. We propose here that, as previously shown by terrestrial (e.g., dinosaurs) and freshwater reptiles (e.g., crocodiles), some groups of turtles also had a wide European distribution during the Early Cretaceous, including both terrestrial and freshwater representatives.

Brodiechelys royoi, B. brodiei, and Larachelus morla are here attributed to Xinjiangchelyidae, a group of freshwater turtles whose presence had been confirmed exclusively from the Middle Jurassic to the Early Cretaceous of Asia. Recent studies have shown that Pan-Cryptodira was a very diverse lineage of turtles in the Early Cretaceous of Europe. The identification of Early Cretaceous European Xinjiangchelyidae and members of the clade that groups “Macrobaenidae” and “Sinemydidae” indicates a close biogeographical relationship in the Early Cretaceous betveen freshwater turtles of Eastern and Western Eurasia.