First report of Plesiochelys etalloni and Tropidemys langii from the Late Jurassic of the UK and the palaeobiogeography of plesiochelyid turtles.
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ABSTRACT:
SUBMITTER: Anquetin J
PROVIDER: S-EPMC4736927 | biostudies-literature | 2016 Jan
REPOSITORIES: biostudies-literature
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Project description:Plesiochelyidae are a major component of Late Jurassic shallow marine environments throughout Europe. However, the taxonomy of plesiochelyid turtles is rather confused. Over the years, many taxa have been synonymized with Plesiochelys etalloni, one of the first described species. However, the holotype of P. etalloni (and only specimen known from Lect, the type locality) was lost for more than 150 years. This specimen has been recently rediscovered in the collections of the Musée d'archéologie du Jura in Lons-le-Saunier, France. For the first time since its original description in 1857, the holotype of P. etalloni is redescribed and compared to relevant material. The taxonomic status of this taxon is revised accordingly. Based on the morphology of the newly rediscovered holotype and on a reassessment of specimens from Solothurn (Switzerland), the species P. solodurensis, P. sanctaeverenae and P. langii are synonymized with P. etalloni. Known skull-shell associations for P. etalloni are re-evaluated in light of the new morphological information available since the rediscovery of this holotype specimen. Finally, we confirm that Plesiochelys is represented by a single species in the Late Jurassic of the Jura Mountains.
| S-EPMC3932733 | biostudies-literature
Project description:Turtles are one of the least explored clades regarding endocranial anatomy with few available descriptions of the brain and inner ear of extant representatives. In addition, the paleoneurology of extinct turtles is poorly known and based on only a few natural cranial endocasts. The main goal of this study is to provide for the first time a detailed description of the neuroanatomy of an extinct turtle, the Late Jurassic Plesiochelysetalloni, including internal carotid circulation, cranial endocast and inner ear, based on the first digital 3D reconstruction using micro CT scans. The general shape of the cranial endocast of P. etalloni is tubular, with poorly marked cephalic and pontine flexures. Anteriorly, the olfactory bulbs are clearly differentiated suggesting larger bulbs than in any other described extinct or extant turtle, and indicating a higher capacity of olfaction in this taxon. The morphology of the inner ear of P. etalloni is comparable to that of extant turtles and resembles those of slow-moving terrestrial vertebrates, with markedly low, short and robust semicircular canals, and a reduced lagena. In P. etalloni the arterial pattern is similar to that found in extant cryptodires, where all the internal carotid branches are protected by bone. As the knowledge of paleoneurology in turtles is scarce and the application of modern techniques such as 3D reconstructions based on CT scans is almost unexplored in this clade, we hope this paper will trigger similar investigations of this type in other turtle taxa.
| S-EPMC3699497 | biostudies-literature
Project description:BackgroundDuring the Late Jurassic, several groups of eucryptodiran turtles inhabited the shallow epicontinental seas of Western Europe. Plesiochelyidae are an important part of this first radiation of crown-group turtles into coastal marine ecosystems. Fossils of Plesiochelyidae occur in many European localities, and are especially abundant in the Kimmeridgian layers of the Swiss Jura Mountains (Solothurn and Porrentruy). In the mid-19th century, the quarries of Solothurn (NW Switzerland) already provided a large amount of fossil turtles, most notably Plesiochelys etalloni, the best-known plesiochelyid species. Recent excavations in the Porrentruy area (NW Switzerland) revealed new fossils of Plesiochelys, including numerous well-preserved shells with associated cranial and postcranial material.Methods/resultsOut of 80 shells referred to Plesiochelys, 41 are assigned to a new species, Plesiochelys bigleri n. sp., including a skull-shell association. We furthermore refer 15 shells to Plesiochelys etalloni, and 24 shells to Plesiochelys sp. Anatomical comparisons show that Plesiochelys bigleri can clearly be differentiated from Plesiochelys etalloni by cranial features. The shell anatomy and the appendicular skeleton of Plesiochelys bigleri and Plesiochelys etalloni are very similar. However, a statistical analysis demonstrates that the thickness of neural bones allows to separate the two species based on incomplete material. This study furthermore illustrates the extent of intraspecific variation in the shell anatomy of Plesiochelys bigleri and Plesiochelys etalloni.
| S-EPMC5493033 | biostudies-literature
Project description:Background. Eucryptodiran turtles from the Late Jurassic (mainly Kimmeridgian) deposits of the Jura Mountains (Switzerland and France) are among the earliest named species traditionally referred to the Plesiochelyidae, Thalassemydidae, and Eurysternidae. As such, they are a reference for the study of Late Jurassic eucryptodires at the European scale. Fifteen species and four genera have been typified based on material from the Late Jurassic of the Jura Mountains. In the past 50 years, diverging taxonomic reassessments have been proposed for these turtles with little agreement in sight. In addition, there has been a shift of focus from shell to cranial anatomy in the past forty years, although most of these species are only represented by shell material. As a result, the taxonomic status of many of these 15 species remains ambiguous, which prevents comprehensive comparison of Late Jurassic turtle assemblages throughout Europe and hinders description of new discoveries, such as the new assemblage recently unearthed in the vicinity of Porrentruy, Switzerland. Methods. An exhaustive reassessment of the available material provides new insights into the comparative anatomy of these turtles. The taxonomic status of each of the 15 species typified based on material from the Late Jurassic of the Jura Mountains is evaluated. New diagnoses and general descriptions are provided for each valid taxon. Results. Six out of the 15 available species names are recognized as valid: Plesiochelys etalloni, Craspedochelys picteti, Craspedochelys jaccardi, Tropidemys langii, Thalassemys hugii, and 'Thalassemys' moseri. The intraspecific variability of the shell of P. etalloni is discussed based on a sample of about 30 relatively complete specimens from Solothurn, Switzerland. New characters are proposed to differentiate P. etalloni, C. picteti, and C. jaccardi, therefore rejecting the previously proposed synonymy of these forms. Based partly on previously undescribed specimens, the plastral morphology of Th. hugii is redescribed. The presence of lateral plastral fontanelles is notably revealed in this species, which calls into question the traditional definitions of the Thalassemydidae and Eurysternidae. Based on these new data, Eurysternum ignoratum is considered a junior synonym of Th. hugii. The Eurysternidae are therefore only represented by Solnhofia parsonsi in the Late Jurassic of the Jura Mountains. Finally, 'Th.' moseri is recognized as a valid species, although a referral to the genus Thalassemys is refuted.
| S-EPMC4034614 | biostudies-literature
Project description:A new ophthalmosaurid ichthyosaur, Thalassodraco etchesi gen. et sp. nov., from the Upper Jurassic Kimmeridge Clay Formation of Dorset, UK is described. The specimen, a partial, articulated skull and anterior thorax in the Etches Collection of Kimmeridge, Dorset, is exceptionally well preserved on a slab of laminated coccolith limestone and has been expertly prepared. It comprises a near complete skull in articulation with associated anterior vertebral column and dorsal ribs, complete pectoral girdle, fully exposed left forelimb, and some elements of the right forelimb. Other elements present, including an ischiopubis are preserved on separate slabs. Presumed rapid burial of the anterior portion of the specimen in the coccolith substrate has preserved a number of ossified ligaments lying across the vertebral column and associated ribs as well as stomach contents and decayed internal organs. Aspects of the dentition, skull roof bones and the forelimb configuration distinguishes the new specimen from previously described Late Jurassic ichthyosaurs. Autopmorphies for T. etchesi include a large rounded protuberance on the supratemporal bone; a thin L-shaped lachrymal, with a steeply curved posterior border; ~ 70 teeth on the upper tooth row, and deep anterior dorsal ribs. A well resolved phylogenetic analysis shows T. etchesi as a member of a basal clade within Ophthalmosauridae comprising Nannopterygius, Gengasaurus, Paraophthalmosaurus and Thalassodraco. The new specimen adds to the diversity of the Ichthyopterygia of the Kimmeridge Clay Formation and emphasises the important contribution of amateur collectors in palaeontology.
| S-EPMC7725355 | biostudies-literature
Project description:Late Jurassic deposits across Europe have yielded a rich fauna of extinct turtles. Although many of these turtles are recovered from marine deposits, it is unclear which of these taxa are habitually marine and which may be riverine species washed into nearby basins, as adaptations to open marine conditions are yet to be found. Two new fossils from the Late Jurassic of Germany provide unusually strong evidence for open marine adaptations. The first specimen is a partial shell and articulated hind limb from the Late Jurassic (early Tithonian) platy limestones of Schernfeld near Eichstätt, which preserves the integument of the hind limb as an imprint. The skin is fully covered by flat, polygonal scales, which stiffen the pes into a paddle. Although taxonomic attribution is not possible, similarities are apparent with Thalassemys. The second specimen is a large, articulated skeleton with hypertrophied limbs referable to Thalassemys bruntrutana from the Late Jurassic (early Late Kimmeridgian) platy limestone of Wattendorf, near Bamberg. Even though the skin is preserved as a phosphatic film, the scales are not preserved. This specimen can nevertheless be inferred to have had paddles stiffened by scales based on the pose in which they are preserved, the presence of epibionts between the digits, and by full morphological correspondence to the specimen from Schernfeld. An analysis of scalation in extant turtles demonstrated that elongate flippers stiffed by scales are a marine adaptation, in contrast to the elongate but flexible flippers of riverine turtles. Phylogenetic analysis suggests that Thalassemys bruntrutana is referable to the mostly Late Jurassic turtle clade Thalassochelydia. The marine adapted flippers of this taxon therefore evolved convergently with those of later clades of marine turtles. Although thalassochelydian fossils are restricted to Europe, with one notable exception from Argentina, their open marine adaptations combined with the interconnectivity of Jurassic oceans predict that the clade must have been even more wide-spread during that time.
| S-EPMC8174742 | biostudies-literature
Project description:A Jurassic salamander, Beiyanerpeton jianpingensis (gen. et sp. nov.), from a recently found site in western Liaoning Province, China is the earliest known record of Salamandroidea. As a Late Jurassic record of the group, it extends the range of the clade by ~40 Ma. The Late Jurassic taxon is neotenic and represented by exceptionally preserved specimens, including fully articulated cranial and postcranial skeletons and bony gill structures close to the cheek region. The fossil beds, consisting of dark-brown volcanic ash shales of the Upper Jurassic Tiaojishan (Lanqi) Formation (Oxfordian), underlie trachyandesite rocks that have yielded a SHRIMP zircon U-Pb date of 157 ± 3 Ma. The fossiliferous beds are substantially older than the Jehol Group, including the Yixian Formation ((40)Ar/(39)Ar dates of 122-129 Ma), but slightly younger than the Middle Jurassic Daohugou horizon ((40)Ar/(39)Ar date of 164 ± 4 Ma). The early fossil taxon shares with extant salamandroids derived character states, including: separated nasals lacking a midline contact, angular fused to the prearticular in the lower jaw, and double-headed ribs on the presacral vertebrae. In contrast to extant salamandroids, however, the salamander shows a discrete and tooth-bearing palatine, and unequivocally nonpedicellate and monocuspid marginal teeth in large and presumably mature individuals. The finding provides insights into the evolution of key characters of salamanders, and also provides direct evidence supporting the hypothesis that the split between Cryptobranchoidea and Salamandroidea had taken placed before the Late Jurassic Oxfordian time. In this aspect, both paleontological and molecular data now come to agree.
| S-EPMC3326464 | biostudies-literature
Project description:BackgroundThere have been numerous studies on dinosaur biogeographic distribution patterns. However, these distribution data have not yet been applied to ecological questions. Ecological studies of dinosaurs have tended to focus on reconstructing individual taxa, usually through comparisons to modern analogs. Fewer studies have sought to determine if the ecological structure of fossil assemblages is preserved and, if so, how dinosaur communities varied. Climate is a major component driving differences between communities. If the ecological structure of a fossil locality is preserved, we expect that dinosaur assemblages from similar environments will share a similar ecological structure.Methodology/principal findingsThis study applies Ecological Structure Analysis (ESA) to a dataset of 100+ dinosaur taxa arranged into twelve composite fossil assemblages from around the world. Each assemblage was assigned a climate zone (biome) based on its location. Dinosaur taxa were placed into ecomorphological categories. The proportion of each category creates an ecological profile for the assemblage, which were compared using cluster and principal components analyses. Assemblages grouped according to biome, with most coming from arid or semi-arid/seasonal climates. Differences between assemblages are tied to the proportion of large high-browsing vs. small ground-foraging herbivores, which separates arid from semi-arid and moister environments, respectively. However, the effects of historical, taphonomic, and other environmental factors are still evident.Conclusions/significanceThis study is the first to show that the general ecological structure of Late Jurassic dinosaur assemblages is preserved at large scales and can be assessed quantitatively. Despite a broad similarity of climatic conditions, a degree of ecological variation is observed between assemblages, from arid to moist. Taxonomic differences between Asia and the other regions demonstrate at least one case of ecosystem convergence. The proportion of different ecomorphs, which reflects the prevailing climatic and environmental conditions present during fossil deposition, may therefore be used to differentiate Late Jurassic dinosaur fossil assemblages. This method is broadly applicable to different taxa and times, allowing one to address questions of evolutionary, biogeographic, and climatic importance.
| S-EPMC2933236 | biostudies-literature
Project description:Modern turtles are composed of two monophyletic groups, notably diagnosed by divergent neck retraction mechanisms. Pleurodires (side-necked turtles) bend their neck sideways and protect their head under the anterior margin of the carapace. Cryptodires (hidden-necked turtles) withdraw their neck and head in the vertical plane between the shoulder girdles. These two mechanisms of neck retraction appeared independently in the two lineages and are usually assumed to have evolved for protective reasons. Here we describe the neck of Platychelys oberndorferi, a Late Jurassic early stem pleurodire, and find remarkable convergent morphological and functional similarities with modern cryptodires. Partial vertical neck retraction in this taxon is interpreted to have enabled fast forward projection of the head during underwater prey capture and offers a likely explanation to the functional origin of neck retraction in modern cryptodires. Complete head withdrawal for protection may therefore have resulted from an exaptation in that group.
| S-EPMC5312562 | biostudies-literature
Project description:To date, only a handful of viruses have been identified in sea turtles. Although eukaryotic circular Rep (replication initiation protein)-encoding single-stranded DNA (CRESS DNA) viruses have been reported from a wide variety of terrestrial species, and some of these viruses have been associated with clinical conditions in certain animals, limited information is available on CRESS DNA viruses from marine life. The present study aimed to investigate the presence of CRESS DNA viruses in sea turtles. In the present study, two (samples T3 and T33) of the 34 cloacal samples from 31 sea turtles (found in ocean waters around the Caribbean Islands of St. Kitts and Nevis) tested positive for CRESS DNA viruses by a pan-rep nested PCR assay. The partial Rep sequence of T3 shared 75.78% of a deduced amino acid (aa) identity with that of a CRESS DNA virus (classified under family Circoviridae) from a mollusk. On the other hand, the complete genome (2428 bp) of T33 was determined by an inverse nested PCR assay. The genomic organization of T33 mirrored those of type II CRESS DNA viral genomes of cycloviruses, characterized by the putative "origin of replication" in the 5'-intergenic region, and the putative Capsid (Cap)- and Rep-encoding open reading frame on the virion-sense- and antisense-strand, respectively. The putative Rep (322 aa) of T33 retained the conserved "HUH endonuclease" and the "super 3 family helicase" domains and shared pairwise aa identities of ~57% with unclassified CRESS DNA viruses from benthic sediment and mollusks. Phylogenetically, the T33 Rep formed a distinct branch within an isolated cluster of unclassified CRESS DNA viruses. The putative Cap (370 aa) of T33 shared maximum pairwise aa identity of 30.51% with an unclassified CRESS DNA virus from a capybara. Except for a blood sample from T33 that tested negative for CRESS DNA viruses, other tissue samples were not available from the sea turtles. Therefore, we could not establish whether the T3 and T33 viral strains infected the sea turtles or were of dietary origin. To our knowledge, this is the first report on the detection of CRESS DNA viruses from sea turtles, adding yet another animal species to the rapidly expanding host range of these viruses. Complete genome analysis of T33 identified a novel, unclassified CRESS DNA virus, providing insights into the high genetic diversity between viruses within the phylum Cressdnaviricota. Considering that sea turtles are an at-risk species, extensive studies on virus discovery, surveillance, and pathogenesis in these marine animals are of the utmost importance.
| S-EPMC10142553 | biostudies-literature