A juvenile pleurosaurid (Lepidosauria: Rhynchocephalia) from the Tithonian of the Mörnsheim Formation, Germany.

Late Jurassic rhynchocephalians from the Solnhofen Archipelago have been known for almost two centuries. The number of specimens and taxa is constantly increasing, but little is known about the ontogeny of these animals. The well-documented marine taxon Pleurosaurus is one of such cases. With over 15 described (and many more undescribed) specimens, there were no unambiguous juveniles so far. Some authors have argued that Acrosaurus, another common component of the Solnhofen Archipelago herpetofauna, might represent an early ontogenetic stage of Pleurosaurus, but the lack of proper descriptions for this taxon makes this assignment tentative, at best. Here, we describe the first unambiguous post-hatchling juvenile of Pleurosaurus and tentatively attribute it to Pleurosaurus cf. P. ginsburgi. The new specimen comes from the Lower Tithonian of the Mörnsheim Formation, Germany. This specimen is small, disarticulated, and incomplete, but preserves several of its craniomandibular bones and presacral vertebrae. It shares with Pleurosaurus a set of diagnostic features, such as an elongated and triangular skull, a low anterior flange in its dentition, and an elongated axial skeleton. It can be identified as a juvenile due to the presence of an unworn dentition, well-spaced posteriormost dentary teeth, a large gap between the last teeth and the coronoid process of the dentary, and poorly ossified vertebrae with unfused neural arches. Acrosaurus shares many anatomical features with both this specimen and Pleurosaurus, which could indicate that the two genera are indeed synonyms. The early ontogenetic stage inferred for the new Pleurosaurus specimen argues for an even earlier ontogenetic placement for specimens referred to Acrosaurus, the latter possibly pertaining to hatchlings.

Paleobiological implications of chevron pathology in the sauropodomorph Plateosaurus trossingensis from the Upper Triassic of SW Germany.

Paleopathology, the study of diseases and injuries from the fossil record, allows for a unique view into the life of prehistoric animals. Pathologies have nowadays been described in nearly all groups of fossil vertebrates, especially dinosaurs. Despite the large number of skeletons, pathologies had never been reported in the sauropodomorph Plateosaurus trossingensis. Here we describe the first pathologies of Plateosaurus using two individuals with pathologies in the chevrons of the tail, from the Upper Triassic of Trossingen, SW Germany. The two specimens each contain three consecutive pathological chevrons. Our results show that the pathologies were caused by external trauma in one individual and potentially tendinous trauma in the other. Healing of the lesions allowed survival of both animals. Using additional pathological specimens found in other collections and from multiple localities, we observe that 14.8% of all individuals of Plateosaurus contain pathologies within their chevrons, suggesting it was a vulnerable bone.

New species of the wasp-mimic Parahephaestion Melzer, 1930 (Coleoptera: Cerambycidae), from Minas Gerais, Brazil, with new records.

A new species, Parahephaestion mimicus sp. nov., is described. Two species are newly recorded for the Brazilian state of Minas Gerais: Sphalloeme costipennis Melzer, 1928 (Cerambycinae, Oemini) and Oreodera omissa Melzer, 1932 (Lamiinae, Acrocinini). Six species are new records for the RPPN Sanctuary of Caraa, (Brazil, Minas Gerais): Thalusia atrata (Melzer, 1918) (Cerambycinae, Rhopalophorini), Trachelissa pustulata (Audinet-Serville, 1834) (Cerambycinae, Trachyderini), Ateralphus dejeani (Lane, 1973) (Lamiinae, Acanthoderini), Phacellocera plumicornis (Klug, 1825) (Lamiinae, Anisocerini), Oncideres impluviata (Germar, 1823), and Psyllotoxus griseocinctus Thomson, 1868 (Lamiinae, Onciderini).

Skull osteology, neuroanatomy, and jaw-related myology of the pig-nosed turtle Carettochelys insculpta (Cryptodira, Trionychia).

The osteology, neuroanatomy, and musculature are known for most primary clades of turtles (i.e., "families"), but knowledge is still lacking for one particular clade, the Carettochelyidae. Carettochelyids are represented by only one living taxon, the pig-nosed turtle Carettochelys insculpta. Here, we use micro-computed tomography of osteological and contrast-enhanced stained specimens to describe the cranial osteology, neuroanatomy, circulatory system, and jaw musculature of Carettochelys insculpta. The jaw-related myology is described in detail for the first time for this taxon, including m. zygomaticomandibularis, a muscular unit only found in trionychians. We also document a unique arterial pattern for the internal carotid artery and its subordinate branches and provide an extensive list of osteological ontogenetic differences. The present work provides new insights into the craniomandibular anatomy of turtles and will allow a better understanding of the evolutionary history of the circulatory system of trionychians and intraspecific variation among turtles.

Thermal Impact and the Relevance of Body Size and Activity on the Oxygen Consumption of a Terrestrial Snail, Theba pisana (Helicidae) at High Ambient Temperatures.

Metabolism, mainly driven by oxygen consumption, plays a key role in life, as it is one of the main ways to respond to extreme temperatures through internal processes. Theba pisana, a widespread Mediterranean land snail, is exposed to a wide range of ambient temperature. In this species the oxygen consumption was tested as a response variable by multiple regression modelling on the "explanatory" variables shell-free mass, temperature, and relative humidity. Our results show that the oxygen consumption of T. pisana can be well described (73.1%) by these three parameters. In the temperature range from 23 °C to 35 °C the oxygen consumption decreased with increasing temperature. Relative humidity, in the range of 67% to 100%, had the opposite effect: if it increases, oxygen consumption will increase as well. Metabolism is proportional to an individual's mass to the power of the allometric scaling exponent α, which is between 0.62 and 0.77 in the mentioned temperature range. CT scans of shells and gravimetry revealed the shell-free mass to be calculated by multiplying the shell diameter to the third power by 0.2105. Data were compared to metabolic scaling exponents for other snails reported in the literature.

Two New Species of Dihammaphora (Coleoptera, Cerambycidae, Rhopalophorini), with Taxonomical and Geographical Notes for the Genus.

Dihammaphora Chevrolat (Arc Nat 1:50-54, 1859) is one of the most diverse genera of Rhopalophorini, with 46 species. It is characterized mainly by species with antennae short and subserrated, with 10 or 11 antennomeres, prothorax cylindrical, and elytra punctuated. In this study, two new species of Dihammaphora are described and illustrated, new records are provided to 11 species, and taxonomic notes are given to six species of the genus. We examined 55 specimens and identified 16 species of the genus Dihammaphora, including Dihammaphora aurea sp. nov. from Honduras, and Dihammaphora cruzi sp. nov. from Brazil. The number of species of Dihammaphora is increased to 48, two of them in Central America, resulting in seven species for this region. In Brazil, 24 species are now recognized, being the country with the largest number of species of the genus. This study shows that there is still a deficit of knowledge about the diversity and distribution of Dihammaphora.

Amphibians and reptiles of the Refúgio Biológico Bela Vista - Itaipu Dam, state of Paraná, southern Brazil / Anfíbios e répteis do Refúgio Biológico Bela Vista - hidrelétrica Itaipu, estado do Paraná, sul do Brasil

Abstract Information regarding species occurrence is fundamental to understanding biodiversity distribution. However, the biodiversity from the west of the state of Paraná has been historically less studied, especially amphibians and reptiles. For this reason, we present the first reptile list of species from the west of the state of Paraná and extend the current list of anurans for the municipality of Foz do Iguaçu. The species list was based on a systematic field study conducted at Refúgio Biológico Bela Vista (RBV) a conservation area within the Hydroelectric Power Itaipu Binacional. We integrated the species list with previous species observations available in the literature for the same place where our sampling was conducted. A total of 41 species of amphibians and reptiles are presented. All amphibians species found were recorded in the field; however, from the 22 species of reptiles recorded, three were historical records obtained before this study. Species were all classified as Least Concern and/or had stable populational status according to the IUCN. Sampling sufficiency was achieved for anurans but not for reptiles, probably due to low abundance of several snake species. The most abundant species of anuran was Dendropsophus nanus, from the Hylidae family, whereas Leptodactylus plaumanni and Scinax squalirostris were represented by only one individual each. The lizard Salvator merianae was the most abundant reptile, and seven species were represented by only one individual each. The most successful sampling method for adult anurans was active search in water bodies whereas most of reptile species were observed by accidental encounters and not through a systematic sampling method. We found that herpetofauna composition from RBV was similar to other communities from Paraná state that also occur within the Semideciduous Seasonal Forest. Finally, as additional information to the species list, we offer species identification keys and discuss the importance of Refúgio Biológico Bela Vista to harbor the anuran and reptile diversity of the region.

Resumo Informações sobre a ocorrência de espécies são fundamentais para a compreensão da distribuição da biodiversidade. Porém, a biodiversidade do oeste do Estado do Paraná tem sido historicamente menos estudada, especialmente a de anfíbios e répteis. Por esse motivo, apresentamos a primeira lista de espécies de répteis do oeste do Estado do Paraná e ampliamos a lista atual de anuros para o município de Foz do Iguaçu. A lista de espécies foi baseada em um estudo sistemático de campo realizado em uma área de conservação dentro da Usina Hidrelétrica Itaipu Binacional. Integramos a lista de espécies com observações de espécies anteriores disponíveis na literatura para o mesmo local onde nossa amostragem foi realizada. Um total de 41 espécies são apresentadas. Todas as espécies de anuros encontradas foram registradas em campo; entretanto, das 22 espécies de répteis registradas, três foram registros obtidos antes deste estudo. Todas as espécies foram classificadas como "Pouco Preocupante" e/ou tinham status de "População Estável" de acordo com a IUCN. A suficiência amostral foi alcançada para anuros, mas não para répteis, provavelmente devido à baixa abundância de diversas espécies de serpentes. A espécie de anuro mais abundante foi Dendropsophus nanus, da família Hylidae, enquanto Leptodactylus plaumanni e Scinax squalirostris foram representados por apenas um indivíduo cada. O lagarto Salvator merianae foi o réptil mais abundante, e sete espécies foram representadas por um indivíduo cada. O método de amostragem mais bem sucedido para anuros adultos foi a busca ativa em corpos d'água, enquanto a maioria das espécies de répteis foi observada por encontros acidentais e não através de um método de amostragem sistematizado. Descobrimos que a composição da herpetofauna do Refúgio Biológico Bela Vista foi semelhante à de outras comunidades do estado do Paraná que também ocorrem dentro da Floresta Estacional Semidecidual. Por fim, como informações adicionais à lista de espécies, oferecemos chaves de identificação das espécies e discutimos sobre a importância da área de Itaipu para abrigar a diversidade de anuros e répteis da região.

Turtle body size evolution is determined by lineage-specific specializations rather than global trends.

Organisms display a considerable variety of body sizes and shapes, and macroevolutionary investigations help to understand the evolutionary dynamics behind such variations. Turtles (Testudinata) show great body size disparity, especially when their rich fossil record is accounted for. We explored body size evolution in turtles, testing which factors might influence the observed patterns and evaluating the existence of long-term directional trends. We constructed the most comprehensive body size dataset for the group to date, tested for correlation with paleotemperature, estimated ancestral body sizes, and performed macroevolutionary model-fitting analyses. We found no evidence for directional body size evolution, even when using very flexible models, thereby rejecting the occurrence of Cope's rule. We also found no significant effect of paleotemperature on overall through-time body size patterns. In contrast, we found a significant influence of habitat preference on turtle body size. Freshwater turtles display a rather homogeneous body size distribution through time. In contrast, terrestrial and marine turtles show more pronounced variation, with terrestrial forms being restricted to larger body sizes, up to the origin of testudinids in the Cenozoic, and marine turtles undergoing a reduction in body size disparity after the extinctions of many groups in the mid-Cenozoic. Our results, therefore, suggest that long-term, generalized patterns are probably explained by factors specific to certain groups and related at least partly to habitat use.

A forged 'chimera' including the second specimen of the protostegid sea turtle Santanachelysgaffneyi and shell parts of the pleurodire Araripemys from the Lower Cretaceous Santana Group of Brazil.

Fossils of Cretaceous sea turtles adapted to an open marine lifestyle remain rare finds to date. Furthermore, the relationships between extant sea turtles, chelonioids, and other Mesozoic marine turtles are still contested, with one key species being Santanachelys gaffneyi Hirayama, 1998, long considered the earliest true sea turtle. The species is an Early Cretaceous member of Protostegidae, a controversial clade either placed within or closely related to Chelonioidea or, alternatively, along the stem lineage of hidden-neck turtles (Cryptodira) and representing an independent open marine radiation. Santanachelys gaffneyi is one of the most completely preserved early protostegids and is therefore critical for establishing the global phylogenetic position of the group. However, the single known specimen of this taxon is yet to be described in detail. Here we describe a second specimen of Santanachelys gaffneyi from its type horizon, the Romualdo Formation (late Aptian) of the Santana Group of the Araripe basin, NE Brazil. The skeletal elements preserved include the posterior part of the skull, neck vertebrae, shoulder girdle, anterior-most and left/central part of the carapace with few peripherals, and plastron lacking most of the hyoplastra. The remaining part of the carapace was apparently completed by fossil dealers using an anterior part of the pleurodiran Araripemydidae, tentatively identified as a shell portion of cf. Araripemys barretoi, a more common Santana fossil turtle, among other indeterminate turtle shell fragments. The purpose of this paper is to report the repatriation of the specimen to Brazil and to provide a preliminary description. Supplementary Information: The online version contains supplementary material available at 10.1186/s13358-023-00271-9.

Different, but the same: Inferring the hunting behaviour of the hypercarnivorous bush dog (Speothos venaticus) through finite element analysis.

Cerdocyonina is a clade composed by the South-American canids in which the bush dog (Speothos venaticus) is one of the most elusive species. Known for its unique morphology within the group, this small, bear-like faced canid is the only member of the clade adapted to hypercarnivory, an almost exclusively meat-based diet currently present only in usually large, pack-hunting canids such as the grey wolf (Canis lupus). However, much of the biology of the bush dog is poorly understood, and inferences about its ecology, hunting strategies and diet are usually based on observation of captive individuals and anecdotal records, with reduced quantitative data to offer support. Here, we investigated the craniomandibular functional morphology of the bush dog through finite element analysis (FEA). FEA was employed to model the biting behaviour and to create extrinsic and intrinsic functional scenarios with different loads, corresponding to different bites used to subdue and process the prey. For comparison, the same modelling was applied to the skull of a grey wolf and a grey fox (Urocyon cinereoargenteus). Our analysis showed that the bush dog's responses to loading are more similar to the wolf's than to the fox's in most scenarios, suggesting a convergent craniomandibular functional morphology between these two hypercarnivorous species, despite their distinct phylogenetic positions and body sizes. Differences between the three taxa are noteworthy and suggested to be related to the size of the usual prey. The modelled bite force for the bush dog is relatively strong, about half of that estimated for the wolf and about 40% stronger than the fox's bite. The results strengthen with quantitative data the inferences of the bush dog as a pack-hunting predator with prey size similar to its own, such as large rodents and armadillos, being specialised in subduing and killing its prey using multiple bites. Its similarity to the wolf also confirms anecdotal accounts of predation on mammals that are much larger than itself, such as peccaries and tapirs. These data highlight the ecological specialisation of this small canid in a continent where large, pack-hunting canids are absent.

Independent origin of large labyrinth size in turtles.

The labyrinth of the vertebrate inner ear is a sensory system that governs the perception of head rotations. Central hypotheses predict that labyrinth shape and size are related to ecological adaptations, but this is under debate and has rarely been tested outside of mammals. We analyze the evolution of labyrinth morphology and its ecological drivers in living and fossil turtles, an understudied group that underwent multiple locomotory transitions during 230 million years of evolution. We show that turtles have unexpectedly large labyrinths that evolved during the origin of aquatic habits. Turtle labyrinths are relatively larger than those of mammals, and comparable to many birds, undermining the hypothesis that labyrinth size correlates directly with agility across vertebrates. We also find that labyrinth shape variation does not correlate with ecology in turtles, undermining the widespread expectation that reptilian labyrinth shapes convey behavioral signal, and demonstrating the importance of understudied groups, like turtles.

Cranial ecomorphology of turtles and neck retraction as a possible trigger of ecological diversification.

Turtles have a highly modified body plan, including a rigid shell that constrains postcranial anatomy. Skull morphology and neck mobility may therefore be key to ecological specialization in turtles. However, the ecological signal of turtle skull morphologies has not been rigorously evaluated, leaving uncertainties about the roles of ecological adaptation and convergence. We evaluate turtle cranial ecomorphology using three-dimensional geometric morphometrics and phylogenetic comparative methods. Skull shape correlates with allometry, neck retraction capability, and different aquatic feeding ecologies. We find that ecological variables influence skull shape only, whereas a key functional variable (the capacity for neck retraction) influences both shape and size. Ecology and functional predictions from three-dimensional shape are validated by high success rates for extant species, outperforming previous two-dimensional approaches. We use this to infer ecological and functional traits of extinct species. Neck retraction evolved among crownward stem-turtles by the Late Jurassic, signaling functional decoupling of the skull and neck from the shell, possibly linked to a major episode of ecomorphological diversification. We also find strong evidence for convergent ecological adaptations among marine groups. This includes parallel loss of neck retraction, evidence for active hunting, possible grazing, and suction feeding in extinct marine groups. Our large-scale assessment of dietary and functional adaptation throughout turtle evolution reveals the timing and origin of their distinct ecomorphologies, and highlights the potential for ecology and function to have distinct effects on skull form.

Tartarugas tem um plano corpóreo bastante modificado, que inclui um casco rígido que restringe sua anatomia pós-craniana. Portanto, a morfologia craniana e a mobilidade do pescoço devem ser centrais nas especializações ecológicas de tartarugas. No entanto, o sinal ecológico das diferentes morfologias de crânio de tartarugas não foi ainda rigorosamente avaliado, deixando incertezas sobre os papéis de adaptações ecológicas e convergência. Avaliamos a ecomorfologia craniana de tartarugas utilizando morfometria geométrica tridimensional e métodos filogenéticos comparativos. A forma craniana correlaciona com alometria, capacidade de retração do pescoço e diferentes ecologias alimentares aquáticas. Encontramos que variáveis ecológicas influenciam apenas a forma do crânio, enquanto uma importante variável funcional (a capacidade de retração do pescoço) influencia tanto a forma como o tamanho do crânio. Predições ecológicas e funcionais para espécies viventes a partir de formas tridimensionais são validadas com altas taxas de sucesso, superando abordagens bidimensionais. Utilizamos isso para inferir traços ecológicos e funcionais de espécies extintas. A retração do pescoço evoluiu em linhagens extintas mais próximas à origem do grupo-coronal durante o Jurássico Final, indicando uma dissociação funcional entre crânio e pescoço do casco, algo possivelmente ligado a um importante episódio de diversificação ecomorfológica. Também encontramos forte evidência para adaptações ecológicas convergentes em grupos marinhos. Isso inclui a perda paralela da retração do pescoço, evidência de caça ativa, alimentação por sucção, além de possível preferência por plantas aquáticas em grupos marinhos extintos. Nosso estudo de larga-escala sobre adaptações funcionais e relacionadas à dieta ao longo da evolução de tartarugas revela o tempo e origem de suas distintas ecomorfologias, e destaca ainda o potencial de ecologia e função terem efeitos distintos sobre a forma craniana.

A unique predator in a unique ecosystem: modelling the apex predator within a Late Cretaceous crocodyliform-dominated fauna from Brazil.

Theropod dinosaurs were relatively scarce in the Late Cretaceous ecosystems of southeast Brazil. Instead, hypercarnivorous crocodyliforms known as baurusuchids were abundant and probably occupied the ecological role of apex predators. Baurusuchids exhibited a series of morphological adaptations hypothesized to be associated with this ecological role, but quantitative biomechanical analyses of their morphology have so far been lacking. Here, we employ a biomechanical modelling approach, applying finite element analysis (FEA) to models of the skull and mandibles of a baurusuchid specimen. This allows us to characterize the craniomandibular apparatus of baurusuchids, as well as to compare the functional morphology of the group with that of other archosaurian carnivores, such as theropods and crocodylians. Our results support the ecological role of baurusuchids as specialized apex predators in the continental Late Cretaceous ecosystems of South America. With a relatively weak bite force (~600 N), the predation strategies of baurusuchids likely relied on other morphological specializations, such as ziphodont dentition and strong cervical musculature. Comparative assessments of the stress distribution and magnitude of scaled models of other predators (the theropod Allosaurus fragilis and the living crocodylian Alligator mississippiensis) consistently show different responses to loadings under the same functional scenarios, suggesting distinct predatory behaviors for these animals. The unique selective pressures in the arid to semi-arid Late Cretaceous ecosystems of southeast Brazil, which were dominated by crocodyliforms, possibly drove the emergence and evolution of the biomechanical features seen in baurusuchids, which are distinct from those previously reported for other predatory taxa.

Feeding biomechanics suggests progressive correlation of skull architecture and neck evolution in turtles.

The origin of turtles is one of the most long-lasting debates in evolutionary research. During their evolution, a series of modifications changed their relatively kinetic and anapsid skull into an elongated akinetic structure with a unique pulley system redirecting jaw adductor musculature. These modifications were thought to be strongly correlated to functional adaptations, especially to bite performance. We conducted a series of Finite Element Analyses (FEAs) of several species, including that of the oldest fully shelled, Triassic stem-turtle Proganochelys, to evaluate the role of force distribution and to test existing hypotheses on the evolution of turtle skull architecture. We found no support for a relation between the akinetic nature of the skull or the trochlear mechanisms with increased bite forces. Yet, the FEAs show that those modifications changed the skull architecture into an optimized structure, more resistant to higher loads while allowing material reduction on specific regions. We propose that the skull of modern turtles is the result of a complex process of progressive correlation between their heads and highly flexible necks, initiated by the origin of the shell.

A taxonomic reassessment of Piramys auffenbergi, a neglected turtle from the late Miocene of Piram Island, Gujarat, India.

BACKGROUND: Piramys auffenbergi was described as an emydine turtle based on a well-preserved skull retrieved from late Miocene deposits exposed on Piram Island, India. The description and figures provided in the original publication are vague and do not support assignment to Emydinae. This taxon has mostly been ignored by subsequent authors. MATERIAL AND METHODS: We reexamine the holotype specimen, provide an extensive description and diagnosis for Piramys auffenbergi, and include this taxon in a global character-taxon matrix for Pleurodira. RESULTS: The presence of a processus trochlearis pterygoidei conclusively shows pleurodiran affinities for Piramys auffenbergi. Inclusion of this taxon in a phylogenetic analysis retrieves it within Stereogenyini closely related to the Asian taxa Shweboemys pilgrimi and Brontochelys gaffneyi. DISCUSSION: Our reexamination of the holotype of Piramys auffenbergi confidently rejects the original assessment of this taxon as an emydine testudinoid and conclusively shows affinities with the pleurodiran clade Stereogenyini instead. Even though most taxa from this lineage are thought to be coastal turtles, all Asian stereogenyines were collected from continental deposits, suggesting a more diverse paleoecology for the group.

Phylogeny, biogeography and diversification patterns of side-necked turtles (Testudines: Pleurodira).

Pleurodires or side-necked turtles are today restricted to freshwater environments of South America, Africa-Madagascar and Australia, but in the past they were distributed much more broadly, being found also on Eurasia, India and North America, and marine environments. Two hypotheses were proposed to explain this distribution; in the first, vicariance would have shaped the current geographical distribution and, in the second, extinctions constrained a previously widespread distribution. Here, we aim to reconstruct pleurodiran biogeographic history and diversification patterns based on a new phylogenetic hypothesis recovered from the analysis of the largest morphological dataset yet compiled for the lineage, testing which biogeographical process prevailed during its evolutionary history. The resulting topology generally agrees with previous hypotheses of the group and shows that most diversification shifts were related to the exploration of new niches, e.g. littoral or marine radiations. In addition, as other turtles, pleurodires do not seem to have been much affected by either the Cretaceous-Palaeogene or the Eocene-Oligocene mass extinctions. The biogeographic analyses highlight the predominance of both anagenetic and cladogenetic dispersal events and support the importance of transoceanic dispersals as a more common driver of area changes than previously thought, agreeing with previous studies with other non-turtle lineages.

Review of the fossil matamata turtles: earliest well-dated record and hypotheses on the origin of their present geographical distribution.

The matamata (Chelus fimbriatus) is a highly aquatic chelid turtle known exclusively from northern South America. Due to its extremely modified morphology, it is well circumscribed among living taxa, but that is not the case of the two extinct species ascribed to the taxon, Chelus colombianus and Chelus lewisi. These were originally described for the Miocene of Colombia and Venezuela, respectively, and are known mostly from post-cranial material. Few traits have been considered diagnostic for these fossil taxa, and their shared geographic and temporal distributions raise doubts about their distinctiveness. Here, we describe new turtle remains from the early Miocene Castillo Formation, at Cerro la Cruz, northwestern Venezuela, assigning them to C. colombianus. We also review the taxonomy and diagnostic features of the fossil species of Chelus, comparing them with the variation recognized within C. fimbriatus. All alleged differences between the fossil Chelus species were found in our sample of the extant species, and may represent intraspecific variation of a single fossil species. Further, we reviewed the fossil record of Chelus spp. and proposed a paleobiogeographic hypothesis to explain its present geographic range.

The last marine pelomedusoids (Testudines: Pleurodira): a new species of Bairdemys and the paleoecology of Stereogenyina.

The extinct Stereogenyina turtles form a relatively diverse Podocnemididae lineage, with twelve described and phylogenetically positioned species. They are characterized by a wide geographic and temporal range, from the Eocene of Africa to the Pleistocene of Southeast Asia, and a peculiar palate morphology, with a secondary palate that is unique among side-necked turtles. Here, we describe a new Stereogenyina species, based on an almost complete skull from the middle Miocene Capadare Formation, of Venezuela. A new phylogenetic analysis supports the assignment of the new species to the genus Bairdemys. Based on geometric morphometrics analyses, we related the development of the stereogenyin secondary palate with the acquisition of a durophagous diet. Based on a review of the sedimentary environments where their fossils are found, we also propose that stereogenyins were a marine radiation of podocnemidid turtles, as corroborated by previous studies of fossil eggs and limb morphology. These two inferences allowed us to hypothesize that stereogenyins occupied an ecological niche similar to that of the extant Carettini sea turtles, and that the rise of the latter group may be related to the Stereogenyina diversity fall in the end of the Miocene.