With advances in molecular phylogeny, the Ursidae affinity of Ailuropoda is no longer controversial. However, the early evolution of Ailuropoda and its close relatives (the tribe Ailuropodini) is still unclear. In this study, we describe a new fossil discovery from Bulgaria, which represents a new taxon of Ailuropodini, ?Agriarctos nikolovi. The materials of Ailurarctos are restudied and the evolution and dispersal of Ailuropodini are discussed. Early Ailuropodini split into two lineages, one in Europe as Agriarctos (three species, whose assignment to the same genus is not certain), and one in southeastern Asia as Ailurarctos and later Ailuropoda. Ailurarctos is a paraphyletic group, with both known species as successive direct ancestors to Ailuropoda. Subtribe Ailuropodina is proposed here to include Ailurarctos and Ailuropoda. Turolian European Agriarctos paralleled with Ailuropodina in many aspects, which reflects similar adaptation towards a specific herbivorous diet.

The northern-most occurrence of Sauropoda in South America was collected in the 1940s from Early–Middle Jurassic-aged continental sediments on the western flank of the Serranía del Perijá in Colombia. Relocation of the site and re-preparation of the specimen, a well-preserved dorsal vertebra, provide important information about the initial diversification of sauropods at low latitudes. The specimen possesses autapomorphies and a unique combination of character states (e.g., divided centropostzygapophyseal lamina, strongly dorsally arched postzygapophyseal facets) that diagnose it as the new genus and species Perijasaurus lapaz. A medium-sized early eusauropod, Perijasaurus inhabited tropical lowland forested areas around the Toarcian–Aalenian boundary. Our phylogenetic analysis recovers Perijasaurus near the base of Eusauropoda, in an unresolved position near Cetiosaurus, Patagosaurus and kin (Bagualia, Spinophorosaurus, Nebulasaurus), and more deeply nested eusauropods. The phylogenetic position of Perijasaurus bolsters the idea that eusauropods achieved a broad geographic distribution during the Early–Middle Jurassic, before the deeper fragmentation of Pangea and after the Toarcian faunal turnover documented at high southern latitudes. Perijasaurus and other basally diverging sauropods display an intermediate level of bone weight reduction in the axial column that represents an antecedent to the more highly developed pneumatic system characterizing Neosauropoda.

La ocurrencia más septentrional de Sauropoda en América del Sur se recolectó en la década del 1940 en sedimentos continentales del Jurásico Inferior a Medio, en el flanco occidental de la Serranía del Perijá en Colombia. La relocalización del sitio y una nueva preparación del espécimen, correspondiente a una vértebra dorsal bien conservada, brindan información importante acerca de la diversificación inicial de los saurópodos en paleolatitudes bajas. El espécimen tiene autapomorfías y una combinación única de caracteres morfológicos (por ejemplo, lámina centropostzigoapofiseal dividida, facetas postzigoapofiseales fuertemente arqueadas dorsalmente) que lo diagnostican como un nuevo género y especie, Perijasaurus lapaz. Perijasaurus es un eusaurópodo de tamaño mediano, que habitó en áreas boscosas en tierras bajas tropicales alrededor del límite Toarciano-Aaleniano. Nuestro análisis filogenético muestra a Perijasaurus cerca de la base de Eusauropoda, en una posición ambigua cercana a Cetiosaurus, Patagosaurus y sus parientes (Bagualia, Spinophorosaurus, Nebulasaurus), y eusaurópodos anidados más profundamente. La posición filogenética de Perijasaurus refuerza la idea de que los eusaurópodos alcanzaron una amplia distribución geográfica durante el Jurásico Temprano-Medio, antes de la fragmentación completa de Pangea y posterior al recambio faunístico del Toarciano documentado en las altas latitudes del sur. Perijasaurus y otros miembros basales de saurópodos muestran un nivel intermedio de reducción de la masa ósea en la columna vertebral que representa un precursor del sistema neumático más desarrollado que caracteriza a Neosauropoda.

Billfishes include some of the largest pelagic teleostean species, but several aspects about their morphology, paleobiology, and evolution remain ambiguous. Their fossil record is fragmentary and mostly represented by rostral and skull remains. Here, we present a comparative study of the caudal vertebral morphology of extant istiophorid species and we use this information to describe two fossil vertebrae from the Gatun and Chagres formations, both from the late Miocene of Panama. The caudal vertebra from the Gatun Fm. is characterized by the presence of a lateral apophysis and identified as Makaira sp., while the vertebra from the Río Indio Member of Chagres Fm. lacks this structure and its morphology indicates a different genus. The estimated total length of the Makaira sp. specimen from Gatun Fm. is about 5.18 m, the largest size calculated for a marlin, while the Rio Indio specimen was about 2.56 m long. Phylogenies show that the radiation of most living istiophorid species seemingly occurred during the Pliocene. However, our results highlight that the genus Makaira and the taxa lacking the lateral apophyses occurred during the late Miocene, showing that the radiation of istiophorids most likely occurred before the Pliocene (ca. 5 Ma).

A new enchodontoid, †Spinascutichthys pankowskiae gen. et sp. nov. is described from the marine Cenomanian deposits of the En Nammoura locality, Lebanon. The enchodontoid is small, but fully ossified, and armoured with rows of scutes bearing strong spines along the back, flanks, and ventral surface of the tail. The long, slender body and elongate jaws are similar to those of dercetids, but the predorsal scutes and ventral prongs on the dentary indicate relationship with enchodontids. Although more, or better, characters are needed to resolve the phylogeny and monophyly of the †Enchodontoidei, the family †Enchodontidae is found to be monophyletic, but a monophyletic †Dercetidae is not recovered. The new taxon is resolved in a phylogenetic analysis as the sister group to †Nardorex. This small, armoured fish supports the interpretation of En Nammoura as having a shallower water environment than that represented at the two similarly aged Lebanese deposits of Hakel and Hadjula.

The reflected lamina of the angular has long been portrayed as a key component in understanding the evolution of the mammalian mandible and middle ear, yet the function of this structure in non-mammalian therapsids remains uncertain. We undertake a broad scale survey of two aspects of the reflected lamina that have been poorly characterized: the ridges and fossae on its lateral surface and the extent of the underlying angular cleft. These two features were visualized in a wide range of therapsids using CT data from the literature and blue light surface scanning. Most species exhibit a clade-specific pattern of surface topography, although dicynodonts are highly variable. A striking similarity in the general number and orientation of fossae and ridges is seen between the otherwise disparate therapsid clades, and we propose homologies in these surface features across Therapsida. These features may serve as useful phylogenetic characters in analyses of the relationships among the major therapsid clades. The angular cleft does not underlie all of what is often referred to as the ‘reflected lamina’ in the literature, and an updated definition of this term is provided. Several therapsid groups independently expanded the angular cleft to further separate the reflected lamina from the angular body. We discuss some functional consequences of our findings and note inconsistency between proposed clade-specific muscle attachment sites and the presence of homologous fossae and ridges across much of Therapsida.

Hybodontiform shark teeth, cephalic and fin spines as well as placoid scales are reported here for the first time from the continental, Lower Triassic Dongchuan Formation near the village of Zhaojia (Huize County, Yunnan Province) in south-west China. The isolated teeth are assigned to three unidentified hybodontiforms but also to a new species of Parvodus, P. huizodus sp. nov., the oldest record of this small-toothed lonchidiid shark genus, extending its range well down into the Lower Triassic. This new species, together with additional hybodontiform remains, provides new evidence of shark occurrences in the aftermath of the end-Permian mass extinction event, when freshwater environments might have acted as centers of origin rather than refugia for sharks. A review of the species assigned to Parvodus and similar small hybodontiform sharks reveals two distinct ecomorphological groups. Group 1, which is characterized by clutching-type dentitions, includes eight species (three of which remain unnamed) ranging from the Middle Triassic to Lower Cretaceous, while group 2, characterized by cutting-crushing type dentitions, comprises 11 species (six of which remain unnamed) including the type-species, P. rugianus ranging from the Lower Triassic to the Lower Cretaceous. The new fossils documented here reveal that hybodontiforms were already adapted to freshwater environments in the Lower Triassic rather than in the Jurassic in China.

The postcranial skeleton of the gliding neodiapsid reptile Coelurosauravus elivensis (Lower Sakamena Formation, ?upper Permian, southwestern Madagascar) is re-described in detail based on all previously referred specimens. The exquisite preservation of the material provides three-dimensional details of the individual bones, which are missing in the Laurasian weigeltisaurid material. A new skeletal reconstruction of C. elivensis is proposed including the first reconstruction of a weigeltisaurid reptile in lateral view. The re-examination of the material highlights interspecific differences in the postcranium of weigeltisaurids, in particular in the trunk and patagial spars. These animals have long been considered as arboreal and gliding reptiles. However, new information on the postcranium of C. elivensis reveals strong similarities with both extant and extinct quadrupeds specialized for a clinging arboreal lifestyle. Additionally, the presence of an additional phalanx in the fifth digit of the manus is now attested for all weigeltisaurids where this region is preserved. We suggest that this morphology could have allowed weigeltisaurids to grasp their patagium as observed in the extant gliding agamid Draco. Weigeltisaurids are thus the earliest known gliding vertebrates and some of the first tetrapods with an obligatory arboreal lifestyle, but also represent the only known vertebrates with a hyperphalangy aligned with a gliding apparatus.

Xenarthra are, very probably, the most basally branching clade among Placentalia, and the result of the so-called “Splendid Isolation” of South America. Although this is the only endemic clade with living representatives, its current diversity is very poor compared with that achieved during most of the Cenozoic. One particular clade, Folivora (living and fossil sloths), includes one of the most enigmatic animals, Thalassocnus, the only genus of the subfamily Thalassocninae. It was originally interpreted as an aquatic sloth taking into account the previous records, which are limited to coastal areas of the latest Miocene and Pliocene of Peru and Chile. Here we present the first record of Thalassocnus from Argentina, which in turn represents the first finding of the genus in a continental sequence. The materials (JUY-P-0180, radius, ulna and part of the articulated left manus) were exhumed from the upper member of the Tafna Formation (Late Miocene–Pliocene) in the eastern Puna (Jujuy Province), Argentina. In agreement with our comparative study, the cladistic analysis corroborates its identification as belonging to the genus Thalassocnus, being placed in a relatively basal location. This finding is of paleobiogeographic and paleoenvironmental significance, due to its location, more than 1171 km away from the Peruvian locality (Sacaco) and more than 750 km from the nearest ones in Chile (Caldera). This extends the geographic range from 76°W to 65°53′W, and from typical littoral environments, to clearly more terrestrial ones. The evolutionary and paleobiogeographic history of Thalassocnus is more complex than previously interpreted.

During fish growth, short periods of rapid changes (morphological, behavioral, physiological, ecological), or thresholds, are interspersed with longer periods of slower development, the steps. This growth pattern is known as saltatory ontogeny. Thresholds delimit main developmental stages (embryo, larva, juvenile, adult) and are periods where modifications can lead to new life-histories, and ultimately to evolutionary novelties. We sought to determine whether saltatory ontogeny could be recognized in a jawed stem-gnathostome, the Late Devonian antiarch placoderm Bothriolepis canadensis, using an extensive size series (220 specimens: 5–220 mm in armor length). The small specimens of this series reveal a previously undocumented immature feature, a preorbital depression on the premedian and lateral plates of the dermal headshield. This depression is a plesiomorphic condition reputed to be absent in highly nested antiarchs such as B. canadensis, which possess instead a preorbital recess. Our objectives were: to describe the ontogenetic morphological changes of the preorbital area in B. canadensis, including the timing of disappearance of the depression using binomial logistic regressions, and to quantify growth allometries of the premedian and lateral plates, with linear and segmented regressions. We found significant segmented allometric patterns in the premedian plate, suggesting saltatory ontogeny in B. canadensis. Moreover, segmented patterns were congruent with the ontogenetic loss of the preorbital depression. An ecomorphological hypothesis is proposed to explain these simultaneous morphological and morphometric changes in B. canadensis. A similar hypothesis is extrapolated to interpret the innovation of the preorbital recess and loss of the preorbital depression during the antiarch phylogeny.

The Anhangueridae are a clade of toothed pterodactyloid pterosaurs, known from their characteristic anteriorly expanded premaxillae and conspicuous rostral sagittal premaxillary and dentary crests. Most known anhanguerids come from the Lower Cretaceous Romualdo Formation within the Araripe Basin of northeast Brazil. With four currently valid genera and several specimens referred to the clade, anhanguerids are the most abundant and diverse tetrapod group in the Romualdo Formation. However, some studies suggest this diversity may be overestimated, as many taxa have been diagnosed based on subtle differences in their premaxillary crests, a structure argued to be either ontogenetically variable or sexually dimorphic. Here we describe an anterior fragment of a gracile pterosaur rostrum that possesses the single diagnostic feature of Anhanguera (fifth and sixth pairs of dental alveoli smaller than the fourth and seventh), but lacks a sagittal crest. The affinities of the new fossil among other toothed pterosaurs were tested through both cladistic and geometric morphometric approaches, which allow referral of the new specimen to Anhanguera. The absence of a crest in the new specimen of Anhanguera suggests that this structure varies in terms of ontogeny and/or sex, and that perhaps it was influenced by sexual selection.

Rhynchocephalia, a once diverse clade of lizard-like reptiles, had a nearly global distribution during much of the Mesozoic. By the Late Cretaceous rhynchocephalians underwent a marked reduction in their diversity and biogeographic range, with sparse records of only deeply nested taxa (e.g., Sphenodontinae) found in the Upper Cretaceous–Paleocene of Patagonia and the Miocene–Recent of New Zealand. Here we describe a partial dentary with teeth of a rhynchocephalian from the Naskal locality, an intertrappean deposit within the Deccan Traps Volcanic Province in peninsular India. This discovery represents the first Cretaceous–Paleogene (K–Pg) record of a rhynchocephalian outside of Patagonia and: (i) demonstrates the clade had a broader Gondwanan distribution during the Cretaceous than previously appreciated and (ii) reinforces the emerging pattern that Rhynchocephalia were confined to Gondwana after the Early Cretaceous. This further extends the rhynchocephalian record in India, which now spans most of the Mesozoic (Late Triassic to ca. K–Pg boundary). The Naskal rhynchocephalian is a member of Acrosphenodontia based on its regionalized, acrodont marginal dentition. Its hatchling teeth appear to be unique (e.g., crowns mesially tipped, distinct break in slope along distal margin) and most similar in morphology to those of Godavarisaurus lateefi from the Lower–Middle Jurassic of India. Although the Naskal intertrappean most likely was deposited during the latest Maastrichtian, additional fossil sampling across the K–Pg boundary in India is needed to determine whether the Naskal rhynchocephalian was a victim or survivor of the end-Cretaceous mass extinction.

A new fossil lanternfish of the extant genus Stenobrachius, †S. sangsunii sp. nov., is described from the Middle Miocene deposits of the Duho Formation, South Korea. This is the second fossil species of the genus after the Miocene †S. salnikovi from Karaginsky Island in the Bering Sea. The new species differs from its congeners by the presence of six photophores in ventral series, presence of only one, long supracaudal gland, lesser numbers of the caudal and total vertebrae, greater prepelvic distance, and shorter anal fin base. The presence of a representative of this boreal genus in the Duho Formation fossil assemblage hints at climatic conditions comparable with the modern era during the time of deposition of this formation. This new finding indicates a wide distribution range and substantial morphological diversity of the genus in the North-west Pacific during the Neogene.

The relative scarcity of well-preserved fossils from the earliest history of stem lineages often limits our ability to establish robust, broad-based evolutionary patterns. This is certainly the case for the pan-radiation of archosaurs whose earliest stem taxa remain poorly understood relative to the crownward archosauriforms. Trilophosaurus buettneri is a North American Triassic stem archosaur that lies near the base of this expansive pan-radiation. We used CT to study the Trilophosaurus braincase with the goal of elucidating the early pan-archosaur neurocranium and its evolution. Results clarify several problematic characters including variable fusion of the exoccipital, absence of contralateral exoccipital contact, lack of a semilunar depression, and several others. These novel scorings fail to alter most currently accepted tree topologies, but the results are detailed. These data also include the phylogenetically earliest evidence of neurocranial pneumatization among pan-archosaurs, including a parabasisphenoid cavity that is positionally homologous to the median pharyngeal recess of crown archosaurs. These data are not without their problems, but they do allow us to hypothesize the earliest transformations in what became a much more extensive character system in crown archosaurs. Multiple autapomorphies suggest Trilophosaurus was capable of a derived behavioral repertoire, but details remain unclear. For example, Trilophosaurus bears a theropod-like elongation of the anterior semicircular canal but lacks the associated expansion of the lateral canal thought to facilitate bipedality in that group. Our data clarify plesiomorphic conditions for later archosaurian transformations while promoting the hypothesis that pan-archosaurs achieved marked structural and behavioral disparity early in their history.

Although known from more than 180 sites in North America, sites with records of multiple Megalonyx elements and individuals are rare. The Tarkio site in southwestern Iowa is unique with three contemporaneous individuals at different stages of development. Among these is one of the largest (ca. 1286 kg) and most complete adult Megalonyx jeffersonii skeletons (ca. 50%, NISP, 123) known. An intermingled sub-adult (ca. 25%, NISP, 63) represents a comparatively complete skeleton for this ontogenetic stage. A third individual, an infant known only from both scapulae (NISP 2), is commingled with sub-adult remains. Scapula sizes indicate that the two juveniles were 50 and 30% of the adult's size. Differential bone preservation and pattern of scatter shows that the adult decomposed lying on its left side and the remains were partially scavenged. Multiple taphonomic proxies demonstrate that the skeletons were subaerially exposed for a limited period, but fluvial transport was not a factor. These individuals, preserved in the same low-energy microstratigraphic unit, apparently died concurrently and probably represent a Megalonyx social unit. Using mammal body size to estimate life history, the estimated average lifespan for M. jeffersonii was around 19 years; gestation time was about 14 months; the interbirth interval was approximately 3 years; and sexual maturation occurred at around 6.5 years. OSL analysis indicates that the sloths were deposited about 106,000 years ago (MIS substage 5ec). Paleoenvironmental proxies suggest an interglacial environment of open woodland along a stream with marshes, like the environment in southwest Iowa today.

A large mawsoniid coelacanth from the lower part of the marine Kimmeridge Clay Formation of England (Kimmeridgian, Upper Jurassic) is studied here. The material is constituted by a group of bones from the head and shoulder girdle of a considerably large individual (estimated length ca. 1.5 m), including the left angular, left dentary, left prearticular, left palatoquadrate complex, both ceratohyals and right cleithrum. Characters such as the coarse external ornamentation of the angular, and the robustness of the quadrate and the cleithrum allow classification of the individual as a member of the Mawsoniidae; whereas the configuration of external bones of the lower jaw (ornamentation of the angular constituted mainly by longitudinal ridges, the presence of a lateral swelling in the dentary) indicates stronger Gondwanan affinities than previously expected (i.e., with the genus Mawsonia, up to now only recorded in South America by the end of the Jurassic). Considering the above, two alternative evolutionary, paleobiogeographic, and taxonomic scenarios are discussed: (1) the new individual can be referred to the European mawsoniid genus Trachymetopon (Lower–Middle Jurassic), in which case it should be assumed this genus reached the Upper Jurassic, and with a morphological variability higher than previously suspected (including some characters previously assumed as diagnostic for Mawsonia). Or (2) an unknown Mawsonia-like form was present in the Upper Jurassic of Europe. The last scenario puts the identification of isolated elements of European Jurassic giant mawsoniids in a new complex taxonomic and paleobiogeographic context, which will deserve further research.