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Jean- Baptiste-Rene Robinet was a comparatively little known 18th Century French philosopher, who is often cited as a pioneer of evolutionary thought. Robinet adopted an all-pervading vitalism (hyl...

Marine tetrapods quickly diversified and were established as marine top predators after the end-Permian Mass extinction (EPME). Ichthyosaurs were the forerunner of this rapid radiation but the main drivers of the diversification are poorly understood. Cartorhynchus lenticarpus is a basal ichthyosauriform with the least degree of aquatic adaptation, holding a key to identifying such a driver. The unique specimen appeared edentulous based on what was exposed but a CT scanning revealed that the species indeed had rounded teeth that are nearly perpendicular to the jaw rami, and thus completely concealed in lateral view. There are three dental rows per jaw ramus, and the root lacks infoldings of the dentine typical of ichthyopterygians. The well-developed and worn molariform dentition with three tooth rows supports the previous inference that the specimen is not of a juvenile. The premaxilla and the corresponding part of the dentary are edentulous. Molariform dentition evolved three to five times independently within Ichthyosauriformes in the Early and Middle Triassic. Convergent exploitation of hard-shelled invertebrates by different subclades of ichthyosauriforms likely fueled the rapid taxonomic diversification of the group after EPME.

Panzhousaurus rotundirostris Jiang, Lin, Rieppel, Motani and Sun, 2019, is restudied on the basis of a second specimen from the Upper Member of the Guanling Formation near Panzhou City, Guizhou Pro...

Summary: Air-breathing marine predators have been essential components of the marine ecosystem since the Triassic. Many of them are considered the apex predators but without direct evidence—dietary inferences are usually based on circumstantial evidence, such as tooth shape. Here we report a fossil that likely represents the oldest evidence for predation on megafauna, i.e., animals equal to or larger than humans, by marine tetrapods—a thalattosaur (∼4 m in total length) in the stomach of a Middle Triassic ichthyosaur (∼5 m). The predator has grasping teeth yet swallowed the body trunk of the prey in one to several pieces. There were many more Mesozoic marine reptiles with similar grasping teeth, so megafaunal predation was likely more widespread than presently conceived. Megafaunal predation probably started nearly simultaneously in multiple lineages of marine reptiles in the Illyrian (about 242–243 million years ago).

The Middle and early Late Triassic of southern China is well known for a remarkable diversity of marine vertebrates, particularly reptiles, including an abundance of intriguing new forms (e.g., Jiang et al., 2005; Hu et al., 2011; Li et al., 2016). Here we describe a new diapsid from Yunnan Province. It possesses an elongate neck that exhibits a remarkable similarity to that of many Protorosauria, yet in other respects the skull and postcranium are much less derived.The new taxon is part of the so-called Panxian-Luoping Fauna and the deposits correspond to the Upper Member of the Guanling Formation, comprising thin to medium bedded, gray to dark-gray laminated marly limestone and limestone, with several layers of bentonite intercalated in the fossil level at Panxian (Wan, 2002; Motani et al., 2008; Jiang et al., 2009). Their age is Pelsonian (middle Anisian, Middle Triassic) as is indicated by the conodont Nicoraella kockeli Zone (Sun et al., 2006; Zhang et al., 2009). A recent U-Pb study indicates the absolute age of these middle Anisian beds to be close to 244 Ma (Wang et al., 2014).

Thalattosaurs (Thalattosauriformes) form a small clade of extinct diapsid marine reptiles (Nicholls, 1999; Rieppel et al., 2000). Due to the scarcity of fossils and their fragmentary nature, thalat...

Tanystropheus longobardicus is one of the most remarkable and iconic Triassic reptiles. Mainly known from the Middle Triassic conservation Lagerstätte of Monte San Giorgio on the Swiss-Italian border, it is characterized by an extraordinarily long and stiffened neck that is almost three times the length of the trunk, despite being composed of only 13 hyper-elongate cervical vertebrae [1-8]. Its paleobiology remains contentious, with both aquatic and terrestrial lifestyles having been proposed [1, 9-12]. Among the Tanystropheus specimens, a small morphotype bearing tricuspid teeth and a large morphotype bearing single-cusped teeth can be recognized, historically considered as juveniles and adults of the same species [4]. Using high-resolution synchrotron radiation microtomography (SRμCT), we three-dimensionally reconstruct a virtually complete but disarticulated skull of the large morphotype, including its endocast and inner ear, to reveal its morphology for the first time. The skull is specialized toward hunting in an aquatic environment, indicated by the placement of the nares on the top of the snout and a "fish-trap"-type dentition. The SRμCT data and limb bone paleohistology reveal that the large morphotype represents a separate species (Tanystropheus hydroides sp. nov.). Skeletochronology of the small morphotype specimens indicates that they are skeletally mature despite their small size, thus representing adult individuals of Tanystropheus longobardicus. The co-occurrence of these two species of disparate size ranges and dentitions provides strong evidence for niche partitioning, highlighting the surprising versatility of the Tanystropheus bauplan and the complexity of Middle Triassic nearshore ecosystems.

—Records of Early Triassic marine reptiles, when they first emerged after the end Permian mass extinction, are rare. During an excavation at Majiashan, Chaohu, Anhui Province, a new sauropt...

The Xingyi Fauna has been known widely for yielding abundant specimens of the pachypleurosaur sauropterygian Keichousaurus hui, the first Triassic marine reptile described from China (Young, 1958)....

A new species of ichthyosauriform is recognized based on 20 specimens, including nearly complete skeletons, and namedChaohusaurus brevifemoralis. A part of the specimens was previously identified asChaohusaurus chaoxianensisand is herein reassigned to the new species. The new species differs from existing species ofChaohusaurusin a suite of features, such as the bifurcation of the caudal peak neural spine and a short femur relative to trunk length. The specimens include both complete and partially disarticulated skulls, allowing rigorous scrutiny of cranial sutures. For example, the squamosal does not participate in the margin of the upper temporal fenestra despite previous interpretations. Also, the frontal unequivocally forms a part of the anterior margin of the upper temporal fenestra, forming the most medial part of the anterior terrace. The skull of the holotype largely retains three-dimensionality with the scleral rings approximately in situ, revealing that the eyeball was uncovered in two different directions, that is, laterally and slightly dorsally through the main part of the orbit, and dorsally through the medial extension of the orbit into the skull roof. This skull construction is likely a basal feature of Ichthyosauromorpha. Phylogenetic analyses place the new species as a sister taxon ofChaohusaurus chaoxianensis.

The placodonts of the Triassic period (252 201 mya) represent one of the earliest and most extreme specialisations to a durophagous diet of any known reptile group. Exceptionally enlarged crushing tooth plates on the maxilla dentary and palatine cooperated to form functional crushing areas in the buccal cavity. However the extreme size of these teeth combined with the unusual way they occluded constrained how replacement occurred. Using an extensive micro computed tomographic dataset of 11 specimens that span all geographic regions and placodont morphotypes tooth replacement patterns were investigated. In addition the previously undescribed dental morphologies and formulae of Chinese taxa are described for the first time and incorporated into the analysis. Placodonts have a unique tooth replacement pattern and results follow a phylogenetic trend. The plesiomorphic Placodus species show many replacement teeth at various stages of growth with little or no discernible pattern. On the other hand the more derived cyamodontoids tend to have fewer replacement teeth growing at any one time replacing teeth unilaterally and/or in functional units thus maintaining at least one functional crushing area at all times. The highly derived placochelyids have fewer teeth and as a result only have one or two replacement teeth in the upper jaw. This supports previous suggestions that these taxa had an alternative diet to other placodonts. Importantly all specimens show at least one replacement tooth growing at the most posterior palatine tooth plates indicating increased wear at this point and thus the most efficient functional crushing area. © 2014 Anatomical Society.

Largocephalosaurus polycarpon Cheng et al. 2012a was erected after the study of the skull and some parts of a skeleton and considered to be an eosauropterygian. Here we describe a new species of the genus, Largocephalosaurus qianensis, based on three specimens. The new species provides many anatomical details which were described only briefly or not at all in the type species, and clearly indicates that Largocephalosaurus is a saurosphargid. It differs from the type species mainly in having three premaxillary teeth, a very short retroarticular process, a large pineal foramen, two sacral vertebrae, and elongated small granular osteoderms mixed with some large ones along the lateral most side of the body. With additional information from the new species, we revise the diagnosis and the phylogenetic relationships of Largocephalosaurus and clarify a set of diagnostic features for the Saurosphargidae Li et al. 2011. Largocephalosaurus is characterized primarily by an oval supratemporal fenestra, an elongate dorsal ‘rib-basket’, a narrow and elongate transverse process of the dorsal vertebrae, and the lack of a complete dorsal carapace of osteoderms. The Saurosphargidae is distinct mainly in having a retracted external naris, a jugal–squamosal contact, a large supratemporal extensively contacting the quadrate shaft, a leaf-like tooth crown with convex labial surface and concave lingual surface, a closed dorsal ‘rib-basket’, many dorsal osteoderms, a large boomerang-like or atypical T-shaped interclavicle. Current evidence suggests that the Saurosphargidae is the sister-group of the Sauropterygia and that Largocephalosaurus is the sister-group of the Saurosphargis–Sinosaurosphargis clade within the family.

Phalarodon atavus from the Germanic Muschelkalk Basin was previously represented only by cranial elements. Here we report a nearly complete and articulated specimen of P. atavus from the Middle Triassic Luoping Biota, Yunnan, South China. This is the first specimen of P. atavus from outside the Germanic Basin. This discovery demonstrates a peri-Tethyan distribution of P. atavus. The new specimen is also the first one preserving the postcranial anatomy of this species, providing the opportunity to evaluate its sustained swimming ability. Inferences made on its functional morphology suggest that this species was probably adapted for active foraging. Tooth crown morphology suggests that P. atavus may have preferred externally soft prey.

The earliest known herbivorous marine reptile is described from the Middle Triassic of southern China., Newly discovered fossils of the Middle Triassic reptile Atopodentatus unicus call for a radical reassessment of its feeding behavior. The skull displays a pronounced hammerhead shape that was hitherto unknown. The long, straight anterior edges of both upper and lower jaws were lined with batteries of chisel-shaped teeth, whereas the remaining parts of the jaw rami supported densely packed needle-shaped teeth forming a mesh. The evidence indicates a novel feeding mechanism wherein the chisel-shaped teeth were used to scrape algae off the substrate, and the plant matter that was loosened was filtered from the water column through the more posteriorly positioned tooth mesh. This is the oldest record of herbivory within marine reptiles.

On some morphology-based phylogenies of extant snakes the capacity to ingest prey of a diameter larger than the snake's head optimizes as a derived condition of macrostomatan snakes such as boas and pythons. The evolution of macrostomatan jaw mechanics can be traced in the more basal scolecophidian and anilioid snakes, such as blind snakes, thread snakes, pipe snakes, and shield tails. Several recent morphology-based phylogenetic analyses of snake interrelationships including fossil snakes have placed fossil taxa of large body size and/or with a macrostomatan skull structure basal to either all extant snakes, or basal to the Alethinophidia (Anilioidea plus Macrostomata, excluding Scolecophidia). This has led to the characterization of scolecophidians and/or anilioids as “regressed macrostomatans”. These snakes would have lost their macrostomatan feeding capacities in adaptation to a fossorial or secretive mode of life, correlated in some forms such as scolecophidians and uropeltines with miniatur...

Joint expeditions by the American Museum of Natural History and Mongolian Academy of Sciences have recovered significant new remains of the basal monstersaur Gobiderma pulchrum. We describe these new specimens in detail and also revisit the originally described material in order to more fully understand this pivotal anguimorph taxon. The newly discovered specimens include skull and postcranial materials that add dramatically to the understanding of the osteology of Gobiderma pulchrum. We revise the diagnosis of this species, adding to the previously published diagnosis the following character states: premaxillary nasal process is narrowest mediolaterally; postfrontal and postorbital remain unfused; postorbital extends posteriorly for almost the entire length of the supratemporal fenestra; the Vidian canal is posteriorly enclosed by the parabasisphenoid; an anterior coracoid emargination is present; the pelvis is completely fused; and the lateral plantar tubercle is distally placed. A phylogenetic...

A new specimen of the protorosaur Macrocnemus fuyuanensis, from the Zhuganpo Member of the Falang Formation at Fuyuan (Yunnan Province, southwestern China), is described and compared with Macrocnemus bassanii. The new specimen is the first in the genus Macrocnemus that clearly shows details of the preorbital region of the skull. A large, plate-like lacrimal is located in front of the tall, columnar prefrontal that defines the anterior margin of the orbit. A longitudinally oriented nasal groove extends along the anterior two-thirds of the snout, accommodating the external naris at its anterior part. A similar preorbital depression has previously been described for Dinocephalosaurus and it is also reported here for the first time in Tanystropheus. The new specimen confirms the status of Macrocnemus fuyuanensis as a species distinct from Macrocnemus bassanii on the basis of a humerus that significantly exceeds the radius in length. The occurrence of both Macrocnemus and Tanystropheus in southwestern...

A recent article published by Diedrich (2011a, Hist Biol. iFirst online, 1–19, doi: 10.1080/08912963.2011.575938) aspired to provide a complete revision of the known material of the placodont genus Cyamodus Meyer, 1863 from the Germanic Basin of central Europe. It is the latest in a series of similar articles by the same author (see Diedrich 2010, Palaeogeogr Palaeoclimatol Palaeoecol. 285(3–4):287–306; 2011b, Nat Sci. 3(1):9–27 for overview) focussing on the European members of the Placodontia (Reptilia: Sauropterygia), a diverse group of enigmatic marine reptiles known from Triassic shallow marine deposits. In a similar fashion to some previous works by Diedrich (see Tintori 2011, Palaeogeogr Palaeoclimatol Palaeoecol. 300(1–4):205–207 for similar points of criticism), this newest article demonstrates a narrow scope of presenting and discussing data, including omitted articles relevant to the topic, and over-interpretation of results, all with the aim of embedding the idea of placodonts being herbivorou...

A new genus and species of Pachypleurosauria, Dianopachysaurus dingi, gen. et sp. nov., from a recently discovered Middle Triassic Lagerstatte in the Anisian Guanling Formation of Yunnan Province is described. The monophyly of Pachypleurosauria, including all potential Chinese pachypleurosaurs in this study, is supported by the rigorous cladistic analysis conducted here. Phylogenetic relationships of Chinese pachypleurosaurs are clarified. Wumengosaurus occupies the most basal position within Pachypleurosauria. Keichousaurus and Dianopachysaurus form the monophyletic Keichousauridae that is the sister group of all European pachypleurosaurs. Our cladistic analysis also supports a previously proposed paleobiogeographic hypothesis of an eastern Tethyan origin of pachypleurosaurs and their migration into the western Tethyan faunal province. The existence of a long ghost lineage as required by the paleobiogeographic hypothesis is greatly shortened by the discovery of Dianopachysaurus.

A new genus and species of marine reptile is described from the Pelsonian (Anisian, Middle Triassic) of Luoping County, Yunnan Province, southwestern China. This diapsid reptile with a secondarily closed upper temporal fossa is the sister taxon to Saurosphargis from the lower Muschelkalk (Anisian, Middle Triassic) of central Europe. It further emphasizes the close faunal affinities between the Eastern and Western Tethyan realm. The new taxon is convergent on cyamodontoid placodonts in having developed a dorsal body armor composed of small osteoderms. The underlying ribs are transversely broadened so as to establish contact along their length, thus forming a closed dorsal ‘rib basket,’ a unique morphology shared with Saurosphargis.

Species are groups of organisms, marked out by reproductive (replicative) properties. Monophyletic taxa are groups of species, marked out by synapomorphies. In Nelson’s analysis, monophyly and synapomorphy are identical relations. Monophyly and synapomorphy, however, are not equivalent relations. Monophyly is epistemically not accessible, whereas synapomorphy is epistemically accessible through character analysis. Monophyly originates with speciation, the two sister-species that come into being through the splitting of the ancestral species lineage forming a monophyletic taxon at the lowest level of inclusiveness. Synapomorphy provides the empirical evidence for monophyly, inferred from character analysis in the context of a three-taxon statement. If synapomorphy and monophyly were equivalent, phylogenetic systematists should find a single tree, instead of multiple equally parsimonious trees. Understanding synapomorphy as the relevant evidence for phylogenetic inference reveals a category mistake in contemporary phylogenetics: the treatment of morphological characters mapped onto molecular trees as synapomorphies and homoplasies. The mapping of morphological characters onto nodes of a molecular tree results in an empirically empty procedure for synapomorphy discovery. Morphological synapomorphies and homoplasies can only be discovered by morphological and combined analyses. The use of morphology in phylogenetic inference in general is defended by examples from Laurales and Squamata in particular. To make empirical evidence scientifically relevant in order to search for concordance, or dis-concordance, of phylogenetic signal, is certainly more fruitful for phylogenetics than the uncritical mapping of morphological traits on a molecular scaffold. © The Willi Hennig Society 2010.

—Eosauropterygians rapidly diversified in the Anisian (Middle Triassic), a period by which the invertebrates had already completely recovered from the end-Permian mass extinction. The Pelso...

The protorosaur Tanystropheus longobardicus is well known from the Middle Triassic of alpine Europe. It has been described on the basis of a number of specimens that apparently range from juvenile to adult. The largest specimens have a total body length of approximately 3 m. Here we report on the first occurrence of a large tanystropheid from the Middle or early Late Triassic of southwestern China. The new specimen is indistinguishable from the largest specimens of T. longobardicus from Europe, although it lacks a skull. Both the Chinese specimen here described and the European specimens of T. longobardicus are characterized by 13 cervical vertebrae (not 12 as had previously been assumed). The new find, together with a recent specimen of Macrocnemus from Yunnan Province, highlight shared elements of the vertebrate fauna around the coastline of western and eastern Tethys during Middle to Late Triassic times.

The Middle Triassic Panxian fauna is a physical marker and representative record of the rapid recovery of the Triassic marine ecosystem following the Early Triassic stagnant stage after the end-Permian mass extinction. Ten marine reptile taxa have been found from the 1.82–2.10 m-thick fossiliferous level in the Upper Member of the Guanling Formation, which can be subdivided into three marine reptile beds through the analysis on the stratigraphic distributions of fossil reptiles. The Lower Reptile Bed yields the sauropterygians Placodus inexpectatus Jiang et al., 2008 and Lariosaurus hongguoensis Jiang et al., 2006, the ichthyopterygians Xinminosaurus catactes Jiang et al., 2008 and Phalarodon cf. Phalarodon fraasi Merriam, 1910, associated with Mixosaurus panxianensis Jiang et al., 2006, representing a stage of predominance of durophagous taxa. In this bed, the large complete skeletons may reach up to 2.3 m in length, and lithofacies and chemostratigraphic analyses indicate a relatively deep carbonate platform with an oxic water environment near the bottom, as well as a rising sea level. The Middle Reptile Bed yields the sauropterygian Nothosaurus yangjuanensis Jiang et al., 2006 and the archosaur Qianosuchus mixtus Li et al., 2006, associated with Mixosaurus panxianensis Jiang et al., 2006. The fossils in this bed are characterized by its pincering dentition and large overall body size, with the largest possibly exceeding 3 m in length. This bed might represent a time of deepest basin with relatively anoxic condition near the bottom. The Upper Reptile Bed yields the sauropterygians Wumengosaurus delicatomandibularis Jiang et al., 2008, Keichousaurus sp., the protorosaur Dinocephalosaurus orientalis Li, 2003, and the ichthyopterygian Mixosaurus panxianensis Jiang et al., 2006. In this bed, reptilian taxa characterized by suction feeding appeared, and most are less than 1 m long. This bed corresponds to a period of decreasing water depth.

The Hapsidopareiontidae are microsaurian amphibians known only from the Lower Permian of the U.S. The hapsidopareiontid skull has a large temporal embayment that occupies most of the area of the cheek, in which the quadratojugal is either absent (Hapsidopareion) or present and greatly reduced (Llistrofus). the unique holotype skull of Llistrofus pricei is well preserved in soft clay. It was originally prepared and described in dorsal view only, but has now been prepared completely free of the matrix. This permitted the first description of the palate, occiput and mandible along with a redescription of the rest of the skull, resulting in substantial emendation of previously published descriptions. Comparison with the eight known complete and partial skulls of Hapsidopareion lepton demonstrates that the two genera are much more similar than had been recognized earlier. Their continued separation is advocated, however, based on size difference, a small number of osteological differences, and the difficulty of obtaining comparably detailed morphological information for Hapsidopareion, which is less well preserved than the Llistrofus specimen. the new morphological information, combined with results of recently published cladistic analyses, suggests that Hapsidopareion and Llistrofus are the only microsaurs that can at present be assigned to the Hapsidopareiontidae. the large temporal embayment of hapsidopareiontids might be thought to have significant functional implications, possibly including “escape” of jaw adductor musculature onto the skull roof. Detailed consideration of this possibility reveals morphological evidence to the contrary, however, and the functional implications of the embayment remain uncertain.

Summary A classification of higher taxa of primitive snakes is based on a review of their skull structure. Skull characters are analysed by outgroup comparison. The classification is based on a strictly cladistic argumentation. The fossil Dinilysia is treated as a terminal taxon, sequenced in the Linnean classification as a plesion. Dinilysia is considered to be the sister-group of the Alethinophidia. Resume Une classification cladistique des serpents primitifs La classification des taxa superieurs des serpents primitifs est basee sur une analyse de I'anatomie du crane. Les caracteres craniaux sont analyses par comparaison avec des groups voisins. La classification l'est proposee par une argumentation strictement cladistique. Le serpent fossil Dinilysia est considere comme taxon terminal, et il est inch dans la classification cornme plesion. Dinilysia est considere sister-group des Alethinophidiens. Zusamrnenfassung Eine cladistische Klassifkation primitiver Schlungen aufder Grundlage des Schadelbaus Die Klassifikation hoherer Taxa primitiver Schlangen wird mit deren Schadelanatomie begrundet. Die Schadelmerkmale werden durch den Vergleich mit Nachbargruppen gewertet. Die Klassifikation beruht auf einer streng kladistischen Argumentation. Die fossile Schlange Dinilysia wird als ein terminales Taxon aufgefast und im Klassifikationsschema als Plesion aufgefuhrt. Dinilysia wird als Schwestergruppe der Alethinophidia aufgefast.

A well preserved 220-million-year-old fossil from marine deposits of the Late Triassic of Guizhou in southwest China sheds light on the intermediate steps in the acquisition of the unique turtle body-plan. Transitional forms are scarce in this lineage, making this transition one of the mysteries of reptile evolution. The find is the most primitive turtle known. It has a fully developed plastron, the ventral dermal armour, evolved before the carapace, the dorsal (upper) part of the shell structure. In this fossil the carapace consists of neural plates only. This suggest that the carapace developed via ossification of the neural plates and broadening of the ribs — a sequence that echoes the developmental pattern in young turtles today. 220-million-year-old fossils from southwestern China represent the most primitive turtle known, and shed light on intermediate steps in the acquisition of the unique and highly specialized turtle body-plan. The origin of the turtle body plan remains one of the great mysteries of reptile evolution. The anatomy of turtles is highly derived, which renders it difficult to establish the relationships of turtles with other groups of reptiles. The oldest known turtle, Proganochelys from the Late Triassic period of Germany1, has a fully formed shell and offers no clue as to its origin. Here we describe a new 220-million-year-old turtle from China, somewhat older than Proganochelys, that documents an intermediate step in the evolution of the shell and associated structures. A ventral plastron is fully developed, but the dorsal carapace consists of neural plates only. The dorsal ribs are expanded, and osteoderms are absent. The new species shows that the plastron evolved before the carapace and that the first step of carapace formation is the ossification of the neural plates coupled with a broadening of the ribs. This corresponds to early embryonic stages of carapace formation in extant turtles, and shows that the turtle shell is not derived from a fusion of osteoderms. Phylogenetic analysis places the new species basal to all known turtles, fossil and extant. The marine deposits that yielded the fossils indicate that this primitive turtle inhabited marginal areas of the sea or river deltas.

A new primitive ichthyopterygian Xinminosaurus catactes gen. et. sp. nov. is erected based on a complete skeleton from the Middle Triassic Upper Member of the Guanling Formation at Panxian, Guizhou, southwestern China. It has a suite of uniquely derived characters in its dentition, ulna, carpals and tarsals. It is similar to primitive ichthyopterygians in retaining elongated limb bones. The new taxon and a diversity of marine reptiles in Panxian Fauna are the physical markers of the Middle Triassic Biotic radiation. Detailed studies of this fauna will supply essential knowledge on the diversity, migration and paleobiogeographic affinity of Middle Triassic ichthyopterygians.

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Li, Z.-G., D.-Y. Jiang, O. Rieppel, R. Motani, A. Tintori, Z.-Y. Sun, and C. Ji. 2016. A new species of Xinpusaurus (Reptilia, Thalattosauria) from the Ladinian (Middle Triassic) of Xingyi, Guizhou, southwestern China. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1218340.

The naso-frontal joint of snakes is described on the basis of high-resolution X-ray computed tomography scans of single individuals of spirit-preserved snake specimens. The suspension of the snout unit from the braincase at the naso-frontal joint shows some broad evolutionary trends among snakes with potential phylogenetic implications, such as sutured or fused medial frontal flanges formed by the medial frontal pillars and the frontal subolfactory processes (in alethinophidians), the restriction of the usually extended dorsoventral contact of the medial nasal flange with the medial frontal flanges to a dorsal or ventral contact (in macrostomatans), and the transfer of the main element of snout suspension from the nasal to the septomaxilla (in colubroids). Some phylogenetic implications of the morphological characters identified in this study are outlined and discussed.

A pleurodontan iguanian from the Green River Formation (Eocene) is described in detail and named. The new taxon is known only from a single specimen preserving all areas of the body. Although many of the bone surfaces are eroded, almost all of the skeleton is present and some cartilaginous elements are preserved. The new taxon shares important characteristics with the extant anisolepines and leiosaurines, including the morphology and placement of the caudal autotomy planes, the postxiphisternal inscriptional ribs, and notched or fenestrated clavicles that are expanded proximally. This is the earliest complete iguanian known from the Americas and the earliest known iguanian that may be confidently referred to an extant “family.” A phylogenetic analysis including this taxon and other fossil and extant iguanians offers some support for the monophyly of Polychrotidae sensu lato, Tropiduridae sensu lato, and non-acrodont iguanians (Pleurodonta).

The skeleton of a newly discovered, exceptionally preserved specimen of Saniwa ensidens is described in detail. The fossil consists of a complete articulated skeleton exposed in dorsal view. It adds important additional information to our knowledge of the anatomy of this fossil varanoid taxon, including a detailed description of the dermatocranium in dorsal view, complete vertebral counts, and a detailed account of the appendicular skeleton. Cartilage preservation allows the identification of treacheal rings, sternum, inscriptional ribs, epicoracoid and suprascapula. Patches of skin are preserved on dermal skull bones, and scattered scales surround the entire skeleton. Incomplete ossification of carpal and tarsal elements, as well as of epiphyses, indicate that the specimen is not fully mature.

The skull of the rare Malaysian snake Anomochilus leonardi is described in detail on the basis of a high-resolution X-ray computed tomographic scan of a mature specimen. Its skull anatomy is compared with that of Anomochilus weberi, as well as with that of scolecophidians and basal alethinophidians such as Anilius, Cylindrophis, uropeltines and selected Booidea. Anomochilus leonardi is found to be more paedomorphic than Anomochilus weberi. The genus Anomochilus most closely resembles uropeltines in skull anatomy. Both Anomochilus and uropeltines develop a ‘central rod design’ of skull morphology, which requires the presence of medial frontal pillars, in adaptation to burrowing habits. These pillars are an alethinophidian characteristic, absent in the skull of scolecophidians, which develop an ‘outer shell design’ in adaptation to burrowing. These results are discussed in the light of the hypothesis that scolecophidians and basal (i.e. non-macrostomatan) alethinophidians are ‘regressed macrostomatans’. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149, 671–685.

The evolutionary history of sexual selection in the geologic past is poorly documented based on quantification, largely because of difficulty in sexing fossil specimens. Even such essential ecological parameters as adult sex ratio (ASR) and sexual size dimorphism (SSD) are rarely quantified, despite their implications for sexual selection. To enable their estimation, we propose a method for unbiased sex identification based on sexual shape dimorphism, using size-independent principal components of phenotypic data. We applied the method to test sexual selection in Keichousaurus hui , a Middle Triassic (about 237 Ma) sauropterygian with an unusually large sample size for a fossil reptile. Keichousaurus hui exhibited SSD biased towards males, as in the majority of extant reptiles, to a minor degree (sexual dimorphism index −0.087). The ASR is about 60% females, suggesting higher mortality of males over females. Both values support sexual selection of males in this species. The method may be applied to other fossil species. We also used the Gompertz allometric equation to study the sexual shape dimorphism of K . hui and found that two sexes had largely homogeneous phenotypes at birth except in the humeral width, contrary to previous suggestions derived from the standard allometric equation.

© 2015 L. Xing et al. Keichousaurus hui is a small pachypleurosaur (Reptilia: Sauropterygia) from the Triassic of China. Many specimens of various growth stages are known, making them ideal for ontogenetic research. We report 22 new specimens from the Middle Triassic of Xingyi (Guizhou, south China), and combined their skeletal measurements with those from 85 published specimens to analyze the ontogenetic trajectory of sexual dimorphism. An Exploratory Factor Analysis suggests that the largest factors behind morphological disparity within the species are body size followed by gender. Sexual dimorphism is most clearly reflected in selected skeletal ratios that are more pronounced in males than in females. We found that the relative length of femur to body size was useful in gender identification, in addition to three ratios that are traditionally used, namely a distal expansion of the humerus relative to its shaft, humerus length relative to body size, and humerus length relative to femur length. Two distinctive patterns exist in allometric changes of these four ratios. The distal expansion of the humerus is exceptional in that it is equally pronounced in juvenile and adult males and therefore must have been fully established during embryonic growth. The other three features are not pronounced at birth size and subsequently become pronounced during postembryonic growth. However, males and females already show different growth trajectories at birth size even in these three. Therefore, the fate of sexually dimorphic features seems to have already been set during embryonic growth in K. hui.

Traditional wisdom holds that biotic recovery from the end-Permian extinction was slow and gradual and was not complete until the Middle Triassic. Here, we report that the evolution of marine predator feeding guilds and their trophic structure, proceeded faster. Marine reptile lineages with unique feeding adaptations emerged during the Early Triassic (about 248 million years ago), including the enigmatic Hupehsuchus that possessed an unusually slender mandible. A new specimen of this genus reveals a well-preserved palate and mandible, which suggest that it was a rare lunge feeder as also occurs in rorqual whales and pelicans. The diversity of feeding strategies among Triassic marine tetrapods reached their peak in the Early Triassic, soon after their first appearance in the fossil record. The diet of these early marine tetrapods most likely included soft-bodied animals that are not preserved as fossils. Early marine tetrapods most likely introduced a new trophic mechanism to redistribute nutrients to the top 10 m of the sea, where the primary productivity is highest. Therefore, a simple recovery to a Permian-like trophic structure does not explain the biotic changes seen after the Early Triassic.

A new genus and species of protorosaur is described on the basis of material originally referred to Tanystropheus antiquus from the Upper Buntsandstein of the Black Forest, Germany. The new taxon is characterized by eight cervical vertebrae that bear markedly elongate cervical ribs, a shagreen of denticles covering the vomers, palatines and pterygoids, a bifurcate second sacral rib, a well-ossified tarsus with three distal tarsals, and an elongate proximal phalanx on digit five. The status of Tanystropheus antiquus is discussed and, while it is retained, its validity is questioned.

The rostral structure of thalattosaurs is reviewed on the basis of a re-investigation of the holotype of Nectosaurus halius and Thalattosaurus alexandrae. The askeptosaurid genera Askeptosaurus and Anshunsaurus share an elongated, parallel-sided rostrum that terminates in a blunt tip. A diastema separating the premaxillary from the maxillary teeth is absent. The claraziid genera Clarazia and Thalattosaurus share a relatively shorter rostrum that has convergent lateral margins and that terminates in a pointed tip. A diastema separating the premaxillary from the maxillary teeth is present. The well-preserved holotype of Nectosaurus halius shows a highly derived rostral structure. The maxilla is short with an anteriorly truncated (vertical) margin, a narrow but high ascending process, and a dorsally curving medial flange that is in natural articulation with the ventrally deflected vomer. These findings corroborate Peyer's original reconstruction of Hescheleria with a nearly vertically placed premaxilla.

Thin sections through the dentary of two specimens of the Late Cretaceous mosasaur Clidastes propython document the upright (vertical) position of developing replacement teeth. Snakes are the only squamates with replacement teeth that develop in a nearly horizontal, posteriorly inclined position. The thin sections also corroborate the finding in 2003 by M. L. Caldwell, L. A. Bundy, and D. O. Lamourex that interdental ridges fully separate successive teeth at their base in mosasaurs, at least on the dentary. This feature is also seen in alethinophidian snakes among squamates, but it remains unknown for more basal members of the mosasauroid clade, and it is absent in scolecophidian snakes.

We here describe the complete skeletal anatomy of Anshunsaurus huangguoshuensis that previously remained unknown. The description includes a review of the dorsal side of the skull as well as the first description of the ventral side of the skull and of the postcranial skeleton. A new phylogenetic analysis supports the monophyly of Askeptosauridea and Thalattosauridea; Endennasaurus is found to be closely related to Askeptosauridae.

A new species of the genus Nothosaurus from the Lower Muschelkalk of Winterswijk, The Netherlands, shows relatively plesiomorphic features such as a relatively forward position of the pineal foramen. The jugal enters into the ventral margin of the orbit, which would also be regarded as plesiomorphic, were it not that this feature optimizes unequivocally as a reversal and, hence, as a diagnostic (derived) character of the new taxon. The new taxon does not, however, increase the fit of the cladogram for the phylogenetic relationships within Nothosaurus to the stratigraphic record of the genus. The basal position of Nothosaurus juvenilis remains problematic.

The fossil snake species Haasiophis terrasanctus Tchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description of Haasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges. Haasiophis cannot be considered a juvenile specimen of Pachyrhachis. The implications of the presence of well-developed hind limbs in Haasiophis, Pachyrhachis, and Podophis for the cladistic analysis of the phylogenetic interrelationships of these f...

The anatomy of a specimen of Lariosaurus xingyiensis (IVPP V 11866) from the Middle Triassic of southern China is described in detail. The specimen ranks among the best preserved of its genus. Specimen IVPP V 11866 is the first unequivocal record of the occurrence of Lariosaurus in the Triassic of southern China, indeed the first record of this genus outside the western Tethyan province. A cladistic analysis using parsimony found IVPP V 11866 to represent the sister taxon of Lariosaurus calcagnii from the Middle Triassic of the southern Alps. This result reinforces the signal for western Tethyan paleobiogeographic relationships of the Triassic marine reptiles from southern China.

The skeletal material of Wonambi naracoortensis has been re-examined, and used to test its phylogenetic relationships. The skeletal description, and the resulting data matrix, concentrates on characters that can be assessed by observation (on the associated material of Wonambi kept at the South Australian Museum). Macrostomatan affinities of Wonambi prove to be well supported. The taxon nests within Macrostomata, above Xenopeltis and Loxocemus.

A new specimen of an enigmatic hupehsuchian genus is reported. The genus was first recognized by Robert L. Carroll and Zhi-ming Dong in 1991, who refrained from naming it because of the poor quality of the only specimen known at the time. After more than two decades, we finally report a second specimen of this genus, which remained unprepared until recently. The new specimen preserves most of the skeleton except the skull, allowing us to erect a new genus and species, Eretmorhipis carrolldongi. The new species shares many characters with Parahupehsuchus longus, including the strange axial skeleton that forms a bony body tube. However, the body tube is short in the new species, being limited to the pectoral region. The vertebral count and limb morphology considerably differ between the new species and P. longus. The forelimb of E. carrolldongi is markedly larger than its hind limb as in Hupehsuchus nanchangensis but unlike in P. longus. The new species is unique among hupehsuchians in a list of features. It has manual and pedal digits that spread radially, forming manus and pes that are almost as wide as long. The third-layer elements of the dermal armor are unusually large, spanning four vertebral segments, yet there are substantial gaps among them. With the addition of the unique paddle, it is now clear that Hupehsuchia had diverse forelimb morphologies spanning from paddles to flippers, unlike ichthyopterygians that were taxonomically more diverse yet only had flippers.

The skull of Augustasaurus hagdorni from the Middle Triassic of northwestern Nevada is described in detail, and compared to those of Pistosaurus and Plesiosaurus. New information amends the earlier description of the postcranial skeleton of Augustasaurus. Phylogenetic analysis corroborates the sister-group relationship of Augustasaurus and Pistosaurus. These two taxa form a clade that is the sister-group of Plesiosaurus. The paleobiogeographical implication of the sister-group relationship of Augustasaurus and Pistosaurus is discussed and linked to the exotic terrane model.

Rieppel, Olivier (2002): Feeding mechanics in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas. Zoological Journal of the Linnean Society 135 (1): 33-63, DOI: 10.1046/j.1096-3642.2002.00019.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1046/j.1096-3642.2002.00019.x

Pachyrhachis problematicusis an early Upper Cretaceous snake with legs from the Middle East. The taxon is involved in an increasingly controversial debate about the origin and higher-level interrelationships of snakes. Its status is problematic because it combines characters of advanced (macrostomatan) snakes with plesiomorphic squa- mate traits. Two competing hypotheses of relationships have consequently been proposed: (1) Pachyrhachis is the sister group of all other snakes, and links Serpentes with Mosasauroidea; and (2) Pachyrhachis is related to the advanced macrostomatan snakes and has no bearing on the issue of snake origins. In a recent paper published in this journal, Caldwell critically reviewed the status of Pachyrhachis as the sister-taxon of macrostomatan snakes, and concluded that Pachyrhachis is the sister-group of all other snakes instead. In the present paper, we review several aspects of character delimitations as proposed by Caldwell, and corroborate the macrostomatan affinities of Pachyrhachis.

A new specimen of Lariosaurus xingyiensis is described and provides new information on the dermal palate of the skull and the postcranial skeleton. Based on a comprehensive comparison with the holotype specimen, an amended diagnosis of L. xingyiensis is given on the basis of the following features: a medium-sized species of Lariosaurus with jugal absent, longitudinal diameter of upper temporal fenestra about 1.7 times longitudinal diameter of orbit, retroarticular process elongate, clavicles without anterolaterally expanded corners, posterior scapular process (blade) slender and elongate, humerus distinctly shorter than femur, and dorsal process of ilium with distinct tubercular ornamentation. Two phylogenetic analyses of Nothosauridae demonstrate that Nothosaurus as previously conceived is not monophyletic whereas Lariosaurus is a monophylum. Three species previously referred to Nothosaurus are more closely related to Lariosaurus and are hereby reassigned to Lariosaurus, namely, L. juvenilis, L. ...