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The sacrum - consisting of those vertebrae that articulate with the ilia - is the exclusive skeletal connection between the hindlimbs and axial skeleton in tetrapods. Therefore, the morphology of this portion of the vertebral column plays a major role in the evolution of terrestrial locomotion. Whereas most extant reptiles only possess the two plesiomorphic sacral vertebrae, additional vertebrae have been incorporated into the sacrum multiple times independently among early-diverging archosaurian (crocodylians + birds) clades. Phytosauria was a diverse, abundant, and cosmopolitan clade of archosauriforms throughout the Late Triassic, but postcrania of this clade are rarely described and few species-level taxonomic placements of phytosaurian postcranial material are available, potentially hampering knowledge of morphological disparity in the postcranial skeleton among phytosaurs. Here, we describe the sacrum of Smilosuchus adamanensis, a phytosaur recovered from the Upper Triassic Chinle Formation of Arizona. This sacrum consists of the two primordial sacral vertebrae, but has a vertebra incorporated from the trunk into the sacrum (= a dorsosacral) and is therefore the first Late Triassic phytosaur and one of the first non-archosaurian archosauromorphs to be described with more than two sacral vertebrae. Our interpretation of this element as a dorsosacral is justified by the lateral extent of the dorsosacral ribs, clear surfaces of articulation between the distal ends of the dorsosacral ribs and the first primordial sacral ribs, and the scar on the medial surface of each ilium for articulation with each dorsosacral rib. Additionally, we provide the first detailed description of the vertebral junction formed by two anteriorly projecting flanges on the first primordial sacral ribs and their corresponding facets on the centrum of the dorsosacral. Computed tomographic ( CT) imaging reveals that the two primordial sacrals are not co-ossified and that the dorsosacral morphology of this specimen is not the result of obvious pathology. We place this incorporation of a trunk vertebra into the phytosaurian sacrum in a broader evolutionary context, with this shift in vertebral identity occurring at least seven times independently among Triassic archosauriforms, including at least three times in early crocodylian-line archosaurs and at least four times among bird-line archosaurs. Additionally, anteriorly projecting flanges of sacral ribs which articulate with the anterior-adjacent centrum have evolved several times in archosauriforms, and we interpret 'shared' sacral ribs (= a sacral rib that articulates with two adjacent sacral centra more or less equally) present in some archosaurian clades as a more extreme example of this morphology. In extant taxa the highly conserved Hox gene family plays a central role in the patterning of the axial skeleton, especially vertebral identity; therefore, the independent incorporation of a trunk vertebra into the sacrum across multiple archosauriform lineages may suggest a homologous underlying developmental mechanism for this evolutionary trend. [ABSTRACT FROM AUTHOR]

Fossils of Mesozoic terrestrial vertebrates from Lithuania and the wider East Baltic region of Europe have previously been unknown. We here report the first Mesozoic terrestrial vertebrate fossils from Lithuania: two premaxillary specimens and three teeth that belong to Phytosauria, a common clade of semiaquatic Triassic archosauriforms. These specimens represent an uncrested phytosaur, similar to several species within the genera Paleorhinus, Parasuchus, Rutiodon and Nicrosaurus. Because phytosaurs are currently only known from the Upper Triassic, their discovery in northwestern Lithuania (the Šaltiškiai clay-pit) suggests that at least part of the Triassic succession in this region is Late Triassic in age, and is not solely Early Triassic as has been previously considered. The new specimens are among the most northerly occurrences of phytosaurs in the Late Triassic, as Lithuania was approximately 7–10° further north than classic phytosaur-bearing localities in nearby Germany and Poland, and as much as 40° further north than the best-sampled phytosaur localities in North America. The far northerly occurrence of the Lithuanian fossils prompts a review of phytosaur biogeography and distribution, which suggests that these predators were widely distributed in the Triassic monsoonal belt but rarer in more arid regions. [ABSTRACT FROM PUBLISHER]

Abstract: The neotype skull of the Indian phytosaur Parasuchus hislopi Lydekker, 1885 (ISI R42) is re‐evaluated and compared with the type material of other basal phytosaurs. Parasuchus hislopi is extremely similar to species previously placed in Paleorhinus (P. bransoni and P. angustifrons), sharing with them such characters as a series of nodes on the lateral surface of the jugal, paired ridges on the squamosal and a frontal depression. Parasuchus hislopi represents a valid species: it can be distinguished from P. bransoni by a relatively low narial eminence and P. angustifrons by the absence of paired nasal depressions. Inclusion of Parasuchus hislopi in a phylogenetic analysis of phytosaurs recovers it in a well‐supported clade with P. bransoni and P. angustifrons. Parasuchus is considered the senior synonym of Paleorhinus and Arganarhinus. Parasuchus (here considered to include P. hislopi, P. angustifrons, P. bransoni and P. magnoculus) has a broad circum‐Pangaean distribution, with species occurring in the south‐western United States, Morocco, central Europe and India. Phytosaur higher‐level taxonomy is also revised: Parasuchidae is redefined to include ‘Paleorhinus‐grade’ phytosaurs and the later‐diverging Mystriosuchinae (the group formerly known as Phytosauridae), and Pseudopalatinae is renamed Mystriosuchini for reason of priority. [ABSTRACT FROM AUTHOR]

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The examination of endocranial data of archosauriforms has led to advances on the evolution of body size, nerve pathways, and sensory abilities. However, much of that research has focused on bird-line archosaurs, resulting in a skewed view of Archosauria. Phytosauria, a hypothesized sister taxon to or early-branching member of Archosauria, provides a potential outgroup condition. Most previous phytosaur endocranial studies were executed without the use of modern technology and focused on derived members of Phytosauria. We present a comparative CT examination of the internal cranial anatomy of Wannia scurriensis, the most basal known parasuchid phytosaur. Wannia scurriensis shows some overall similarity with extant crocodylians and derived phytosaurs in general endocranial shape, a large hypophyseal fossa, and trigeminal ( CN V) innervation, but as a whole, the endocast has noticeable differences to crocodylians and other phytosaurs. The pineal region is expanded dorsally as in other phytosaurs but also laterally (previously unrecognized). CN V exits the pons in a more dorsal position than in Parasuchus hislopi, Machaeroprosopus mccauleyi, or Smilosuchus gregorii. Wannia scurriensis also exhibits a larger hypophyseal fossa relative to brain size than observed in P. hislopi or S. gregorii, which may indicate more rapid growth. The well-preserved semicircular canals have lateral canals that are angled more anteroventrally than in derived phytosaurs. Extensive facial innervation from the large CN V indicates increased rostrum sensitivity and mechanoreceptive abilities as in Alligator mississippiensis. These endocranial similarities among phytosaurs and with Alligator indicate conserved ecological and functional results of an aquatic lifestyle, and highlight a need for further exploration of endocranial anatomy among Archosauriformes. [ABSTRACT FROM AUTHOR]

Pseudosuchians were the dominant group of archosaurs on continental ecosystems during the Triassic. However, studies that report palaeopathologies based on osteohistological evidence in this group are scarce. Here, two cases of palaeopathologies found in appendicular bones of two clades of pseudosuchians are presented: Aetosauria, a distal fragment of the fibula of Aetosauroides scagliai and Erpetosuchidae, the distal half of the tibia of Tarjadia ruthae from the Ischigualasto and Chañares formations, respectively (province of La Rioja, Argentina). The cortex in both specimens is composed of woven-fibred bone in the deepest part and by parallel-fibred bone in the subperiosteum. Towards the outermost portion of the cortex, a thin layer of periosteal bone with an irregular margin is recorded, mainly formed by a fibrolamellar bone vascularized with relatively wide and anastomosed radial canals. These features are compatible with a specific tissue recognized in pathological conditions, the radial fibrolamellar bone (RFB), generated by periosteal reactive bone. Additionally, a thin layer of parallel-fibred/lamellar bone crossed this structure in A. scagliai and surrounding the outermost portion in both specimens. The presence of RFB shows an abnormally accelerated bony overgrowth. However, due to the short thickness of this layer and the subsequent formation of parallel-fibred bone, it indicates a slowdown in its development and a possible recovery of the pathological condition. The configuration of the injury is compatible with periostitis and it constitutes the first record of this type of pathologies in non-crocodylomorph pseudosuchians. As the causes for this benign injury, it is inferred a non-traumatic stress followed by a pyogenic infection. [ABSTRACT FROM AUTHOR]

Crocodylomorpha is the stem-lineage of modern crocodylians and the only pseudosuchian (i.e. crocodylian-line archosaurs) clade that survived the Triassic–Jurassic mass extinction event. Its earliest members, the non-crocodyliform crocodylomorphs, also known as 'sphenosuchians', were terrestrial and mostly small-bodied (<2 m long), although some large-bodied forms are known. Saltoposuchus connectens is one of the first described crocodylomorph species but it remains poorly studied, in part due to its contentious taxonomy. Here, all referred Saltoposuchus specimens are described in detail for the first time and its taxonomy is revised, with additional taxonomic implications for the British crocodylomorph Terrestrisuchus gracilis and the coelophysoid theropod Procompsognathus triassicus. Saltoposuchus connectens is clearly distinguished from Terrestrisuchus gracilis based on both cranial and postcranial features. The phylogenetic analysis finds that Saltoposuchus connectens , Terrestrisuchus gracilis , and Litargosuchus leptorhynchus form a clade of gracile, long-legged crocodylomorphs, identified as Saltoposuchidae Crush 1984. A histological section of a femur reveals highly vascularized fibrolamellar tissue in the second-largest specimen of Saltoposuchus connectens (SMNS 12596), indicating sustained high growth rates. A similar pattern was previously observed in Terrestrisuchus sp. contrasting with slower growth rates in the crocodylomorph Hesperosuchus agilis. These findings suggest that saltoposuchids had a high resting metabolic rate and active lifestyle. [ABSTRACT FROM AUTHOR]

Metoposaurids are a clade of large-bodied temnospondyls commonly found in non-marine Late Triassic deposits across northern Pangea. Three taxa are known from North America: Anaschisma browni, Apachesaurus gregorii, and "Metoposaurus" bakeri. While the osteology of most metoposaurids has been recently revised, that of a few taxa, including "Metoposaurus" bakeri remains poorly characterized. This taxon was formally described in 1931 as "Buettneria bakeri," and its taxonomy has remained in flux ever since then. "Metoposaurus" bakeri is the earliest appearing metoposaurid in North America (Carnian of Texas), and Metoposaurus has frequently been utilized as an index taxon of the Otischalkian estimated holochron ('land vertebrate faunachron') and for biostratigraphic correlations with other geographic regions. The taxonomy of this species is therefore relevant for both taxonomic experts and biostratigraphers. Here we redescribe all material from the type locality of "M." bakeri, the Elkins Place bone bed, and perform a phylogenetic analysis using a revised matrix assembled from several previous studies. Anatomical comparisons and phylogenetic analyses do not support placement in either Metoposaurus, a taxon otherwise only found in Europe, or Anaschisma, the only other large-bodied taxon from North America. Therefore, we erect a new genus, Buettnererpeton gen. nov., to accommodate this species. Metoposaurus is consequently absent from North America, and this genus cannot be used in global biostratigraphy. Phylogenetic analyses provide evidence that the phylogeny of the Metoposauridae remains extremely labile, with drastic differences in topological resolution and structure being linked to just a handful of characters and scores. Metoposaurids' morphological conservatism and the increased recognition of intraspecific variation thus continue to be major confounds to elucidating the evolutionary history of this clade. [ABSTRACT FROM AUTHOR]

We provide a detailed description of the poorly known reptile Eifelosaurus triadicus Jaekel, 1904 from the Upper Buntsandstein (Triassic: early Anisian) of Oberbettingen in the southwestern Eifel region of Rhineland-Palatinate, Germany. The holotype and only known specimen is a partial postcranial skeleton exposed in ventral view. Since its original description Eifelosaurus triadicus has been almost completely ignored in the literature. Our phylogenetic analysis recovered this taxon within Rhynchosauria and Rhynchosauridae, as the sister taxon to the clade comprising Stenaulorhynchinae and hyperodapedontine-line rhynchosaurids. A unique combination of character states allows distinguishing Eifelosaurus triadicus from other rhynchosaur species with preserved matching postcranial bones. Thus, we tentatively consider this taxon valid until more information about the postcrania of other Early to Middle Triassic rhynchosaurs becomes available. Eifelosaurus triadicus represents a paleobiogeographically important record, showing that rhynchosaurs had already attained a broad paleolatitudinal distribution by the early Middle Triassic. [ABSTRACT FROM AUTHOR]

The historical clade "Protorosauria" represents an important group of archosauromorph reptiles that had a wide geographic distribution between the Late Permian and Late Triassic. "Protorosaurs" are characterized by their long necks, which are epitomized in the genus Tanystropheus and in Dinocephalosaurus orientalis. Recent phylogenetic analyses have indicated that "Protorosauria" is a polyphyletic clade, but the exact relationships of the various "protorosaur" taxa within the archosauromorph lineage is currently uncertain. Several taxa, although represented by relatively complete material, have previously not been assessed phylogenetically. We present a new phylogenetic hypothesis that comprises a wide range of archosauromorphs, including the most exhaustive sample of "protorosaurs" to date and several "protorosaur" taxa from the eastern Tethys margin that have not been included in any previous analysis. The polyphyly of "Protorosauria" is confirmed and therefore we suggest the usage of this term should be abandoned. Tanystropheidae is recovered as a monophyletic group and the Chinese taxa Dinocephalosaurus orientalis and Pectodens zhenyuensis form a new archosauromorph clade, Dinocephalosauridae, which is closely related to Tanystropheidae. The well-known crocopod and former "protorosaur" Prolacerta broomi is considerably less closely related to Archosauriformes than was previously considered. [ABSTRACT FROM AUTHOR]

The fusion of the sacrum occurs in the major dinosaur lineages, i.e. ornithischians, theropods, and sauropodomorphs, but it is unclear if this trait is a common ancestral condition, or if it evolved independently in each lineage, or even how or if it is related to ontogeny. In addition, the order in which the different structures of the sacrum are fused, as well as the causes that lead to this co‐ossification, are poorly understood. Herein, we described the oldest record of fused sacral vertebrae within dinosaurs, based on two primordial sacral vertebrae from the Late Triassic of Candelária Sequence, southern Brazil. We used computed microtomography (micro‐CT) to analyze the extent of vertebral fusion, which revealed that it occurred only between the centra. We also assessed the occurrence of sacral fusion in Dinosauria and close relatives. The degree of fusion observed in representatives of the major dinosaur lineages suggested that there may be a sequential pattern of fusion of the elements of the sacrum, more clearly observed in Sauropodomorpha. Our analyses suggest that primordial sacral vertebrae fuse earlier in the lineage (as seen in Norian sauropodomorphs). Intervertebral fusion is observed to encompass progressively more vertebral units as sauropodomorphs evolve, reaching up to five or more fully fused sacrals in Neosauropoda. Furthermore, the new specimen described here indicates that the fusion of sacral elements occurred early in the evolution of dinosaurs. Factors such as ontogeny and the increase in body size, combined with the incorporation of vertebrae to the sacrum may have a significant role in the process and in the variation of sacral fusion observed. [ABSTRACT FROM AUTHOR]

Rhynchosaurs were quadrupedal, bulky herbivorous archosauromorph diapsids with a highly specialized dental apparatus. This group is restricted to the Triassic Period and became extremely abundant worldwide during the late Carnian, numerically dominating some of the first dinosaur-bearing assemblages. Despite their high abundance in upper Carnian beds of South America, rhynchosaurs are restricted to a handful of specimens in the latest Ladinian–early Carnian tetrapod assemblages of this continent. Here, we improve the record of one of the oldest rhynchosaur assemblages of South America with the detailed description of all the rhynchosaur specimens currently known from the Tarjadia Assemblage Zone (AZ) (late Ladinian–?earliest Carnian) of the Chañares Formation (Ischigualasto-Villa Unión Basin, La Rioja Province). Most of these specimens were only preliminarily reported before, and as part of this revision we name the new taxon Elorhynchus carrolli gen. et sp. nov. based on one of these specimens, which represents the first new taxon for the Chañares Formation in 22 years. Elorhynchus carrolli and three more rhynchosaur specimens from the Chañares Formation are identified as stenaulorhynchine rhynchosaurs based on the presence of a crowded field of numerous lingual teeth in the dentary and the presence of small occlusal teeth in the maxillary tooth plate. Although their morphology is congruent, we did not refer the other stenaulorhynchine specimens to Elorhynchus carrolli because they lack diagnostic overlapping character states between them. Nevertheless, there is no current evidence for the presence of more than one rhynchosaur species in the Chañares Formation. The description of Elorhynchus carrolli and the other stenaulorhynchines from the Chañares Formation reinforces biostratigraphical links with the Dinodontosaurus AZ (Santa Maria Supersequence) of southern Brazil and the Lifua Member of the Manda Beds of Tanzania. [ABSTRACT FROM AUTHOR]

We describe a new eusphenodontian, Lanceirosphenodon ferigoloi gen. et sp. nov., from the Upper Triassic (Norian) Riograndia Assemblage Zone (AZ) of the Candelária Sequence (Santa Maria Supersequence) of Rio Grande do Sul, Brazil. The new taxon consists of an almost complete left dentary with dentition, which exhibits a mosaic of features considered 'typical' of non-eusphenodontian rhynchocephalians, along with others reported for eusphenodontian taxa. It has the typical rhynchocephalian regionalized dentition with 19 teeth and also pleuroacrodont implantation; the additional dentition presents alternation of size and shape, with the last additional teeth resembling a spear in labial view. A well-developed chin is also present. Our phylogenetic analysis places Lanceirosphenodon as one of the most basal eusphenodontians and reinforces the hypothesis that Rhynchocephalia underwent an early diversification, probably in the Early Triassic, followed by an explosion in morphological disparity. Based on the ontogenetic sequence of Sphenodon, Lanceirosphenodon fitted between stages T2 and T3, representing a probable early juvenile individual. In spite of its ontogenetic stage, the set of characters present in Lanceirosphenodon, including two autapomorphies, supports its recognition as a new taxon. This new taxon increases our knowledge of the faunal diversity in the Triassic of Gondwana and more locally for the Riograndia Assemblage Zone of southern Brazil. [ABSTRACT FROM AUTHOR]

Metoposaurids are non-marine temnospondyls that are among the most common constituents of Late Triassic deposits, but despite their abundance, the evolutionary relationships of the group are poorly resolved and have not been fully addressed with modern phylogenetic methods. The genus Anaschisma is one of a number of poorly resolved metoposaurid taxa and was erected to describe two species from the Popo Agie Formation (Carnian) in Wyoming: Anaschisma browni and Anaschisma brachygnatha. Since being named, the genus has been repeatedly synonymized and separated with other taxa in the context of broader revisions of the Metoposauridae. At present, Anaschisma is considered to be an indeterminate metoposaurid. Extensive descriptive work of metoposaurids since the erection of Anaschisma in 1905 and the last taxonomic review of the clade in 1993, including the naming of several new taxa and the reappraisal of several others, has generated a sufficiently detailed database through which to re-evaluate the taxonomy of the Metoposauridae as part of the analysis of phylogenetic relationships of Anaschisma. Here we reappraise and redescribe the holotypes of A. browni and A. brachygnatha to determine their taxonomic status and relationships in the context of an updated and revised metoposaurid phylogenetic framework. Anaschisma browni and Anaschisma brachygnatha are synonymized under the former species, as all previously listed diagnostic differences are compatible with intraspecific variation. Additionally, the well-known Koskinonodon perfectus is found to be a junior synonym of Anaschisma browni, which takes taxonomic precedence given its earlier description. Poor phylogenetic resolution of the Metoposauridae is likely the product of marked morphological conservatism within the clade and limited character sampling, although some patterns of regional clustering are apparent from the analysis. [ABSTRACT FROM AUTHOR]

The lithostratigraphy of the Triassic deposits of the Jameson Land Basin in central East Greenland is revised. The new Scoresby Land Supergroup is now composed of the Wordie Creek, Pingo Dal, Gipsdalen and Fleming Fjord Groups. This paper only deals with the lithostratigraphy of the late Early-Late Triassic continental deposits of the latter three groups with emphasis on the vertebratebearing Fleming Fjord Group. The new Pingo Dal Group consists of three new formations, the Rødstaken, Paradigmabjerg and Klitdal Formations (all elevated from members), the new Gipsdalen Group consists of three new formations, the Kolledalen, Solfaldsdal (with the new Gråklint Member) and Kap Seaforth Formations (all elevated from members), and the new Fleming Fjord Group is subdivided into three new formations, the Edderfugledal, Malmros Klint and Ørsted Dal Formations (all elevated from members). The Edderfugledal Formation contains two cyclic bedded, lacustrine members, a lowermost Sporfjeld Member (elevated from beds), and an uppermost Pingel Dal Member (elevated from beds). The lacustrine red beds of the Malmros Klint Formation are not subdivided. The lacustrine and fluvial Ørsted Dal Formation contains three new members. In the eastern and central part of the basin, the formation is initiated by cyclic bedded, red lacustrine mudstones of the Carlsberg Fjord Member (elevated from beds), while in the northwestern part of the basin the lowermost part of the formation is composed of grey fluvial conglomerates and sandstones with subordinate red mudstones of the Bjergkronerne Member (elevated from beds). The uppermost part of the formations in most of the basin is composed of cyclic bedded, variegated lacustrine mudstones and grey to yellowish marlstones of the Tait Bjerg Member (elevated from beds). The sediments in the Fleming Fjord Group contain remains of a rich and diverse vertebrate fauna including dinosaurs, amphibians, turtles, aeotosaurs, pterosaurs, phytosaurs and mammaliaforms. Most vertebrate bones have been found in uppermost Malmros Klint Formation, and in the Carlsberg Fjord and Tait Bjerg Members. The Norian-early Rhaetian, lacustrine Fleming Fjord Group was deposited at about 41° N on the northern part of the supercontinent Pangaea. Lacustrine sedimentation was controlled by seasonal as well as longer-term (orbital) variation in precipitation. Precipitation was probably brought to the basin by southwesterly winds. The lacustrine sediments of the uppermost Fleming Fjord Group show deposition during increasingly humid conditions changing the lake environment from an ephemeral lake-steppe area to a perennial lake. This evolution of lake environment suggests a change from a winter-wet temperate climate to one with precipitation throughout the year. [ABSTRACT FROM AUTHOR]

The "red siltstone" member of the Upper Triassic Chinle Formation in the Eagle Basin of Colorado contains a diverse assemblage of dinosauromorphs falling outside of Dinosauria. This assemblage is the northernmost known occurrence of non-dinosaurian dinosauromorphs in North America, and probably falls within the Revueltian land vertebrate estimated biochronozone (215-207 Ma, middle to late Norian). Lagerpetids are represented by proximal femora and a humerus referable to Dromomeron romeri. Silesaurids (non-dinosaurian dinosauriforms) are the most commonly recovered dinosauromorph elements, consisting of dentaries, maxillae, isolated teeth, humeri, illia, femora, and possibly a scapula and tibiae. These elements represent a new silesaurid, Kwanasaurus williamparkeri, gen. et sp. nov., which possesses several autapomorphies: a short, very robust maxilla with a broad ascending process, a massive ventromedial process, a complex articular surface for the lacrimal and jugal, and 12 teeth; 14 dentary teeth; an ilium with an elongate and blade-like preacetabular process and concave acetabular margin; a femur with an extremely thin medial distal condyle and a depression on the distal end anterior to the crista tibiofibularis. The recognition of K. williamparkeri further demonstrates the predominantly Late Triassic diversity and widespread geographic distribution across Pangea of the sister clade to Asilisaurus, here named Sulcimentisauria. Silesaurid dentition suggests a variety of dietary specializations from faunivory and omnivory in the Middle Triassic and early Late Triassic (Carnian), to herbivory in the Late Triassic (Carnian and Norian), with the latter specialization possibly coinciding with the radiation of Sulcimentisauria across Pangea. The extremely robust maxilla and folidont teeth of K. williamparkei may represent a strong herbivorous dietary specialization among silesaurids. [ABSTRACT FROM AUTHOR]

Rhynchosauria is a group of archosauromorph reptiles abundant in terrestrial ecosystems of the Middle Triassic. Mesosuchus is one of the earliest and basalmost rhynchosaurs, playing an important role not only for the understanding of the evolution of the group as a whole, but also of archosauromorphs in general. The braincase of Mesosuchus has been previously described, albeit not in detail, and the middle and inner ears were missing. Here, we provide new information based on micro-computed tomography scanning of the best-preserved specimen of Mesosuchus, SAM-PK-6536. Contrary to what has been stated previously, the braincase of Mesosuchus is dorso-ventrally tall. The trigeminal foramen lies in a deep recess on the prootic whose flat ventral rim could indicate the articulation surface to the laterosphenoid, although no such element was found. The middle ear of Mesosuchus shows a small and deeply recessed fenestra ovalis, with the right stapes preserved in situ. It has a rather stout, imperforated and posteriorly directed shaft with a small footplate. These features suggest that the ear of Mesosuchus was well-suited for the detection of low-frequency sounds. The semicircular canals are slender and elongate and the floccular fossa is well-developed. This is indicative of a refined mechanism for gaze stabilization, which is usually related to non-sprawling postures. The most striking feature of the Mesosuchus braincase is, however, the presence of a pneumatic sinus in the basal tubera. The sinus is identified as originating from the pharyngotympanic system, implying ossified Eustachian tubes. Braincase pneumatization has not yet been a recognized feature of stem-archosaurs, but the potential presence of pneumatic foramina in an array of taxa, recognized here as such for the first time, suggests braincase sinuses could be present in many other archosauromorphs. [ABSTRACT FROM AUTHOR]

Prestosuchus chiniquensis is the most famous "rauisuchian" described by Friedrich von Huene, eight decades ago, and several specimens have been assigned to this taxon since then. In the present contribution, we provide the first detailed description of a complete and very well preserved skull (including the braincase) assigned to Prestosuchus chiniquensis from the Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence of southern Brazil. The detailed description of the skull of Prestosuchus chiniquensis, besides increasing the knowledge about this taxon, may help elucidate the taxonomic relationships of pseudosuchians even further, since most of the characters used in phylogenetic analyzes are cranial. The presence of the subnarial fenestra, a controvertial extra opening on the skull of "rauisuchians", is thoroughly discussed considering the evidence provided by this new specimen. We consider that the small slit-opening between the premaxilla and the maxilla in Prestosuchus chiniquensis, can not safely be considered a true fenestra, but indicates more likely the existence of some degree of cranial kinesis between these elements which can result in different relative positions of the bones after definitive burial and fossilization, so that the size and shape of this opening is taphonomically controlled. Complementarily, the digital reconstruction of its cranial endocast was developed both from the observation of the preserved braincase and from CT scan images, which resulted in obtaining the first endocast known for a "rauisuchian". The endocast of Prestosuchus chiniquensis exhibited some remarkable convergences with that of theropod dinosaurs, which could be a reflection of the similar niches they occupied, since "rauisuchians" were the top predators at the end of the Late Triassic, before the extinction of all non-crocodylomorph pseudosuchians. [ABSTRACT FROM AUTHOR]

Erythrosuchidae is a clade of early archosauriform reptiles, which were apex predators in many late Early andMiddle Triassic ecosystems, following the Permo-Triassic mass extinction. Erythrosuchids had a worldwide distribution, with well-preserved fossil material known from South Africa, European Russia, and China. We here redescribe the anatomy and revise the taxonomy of Guchengosuchus shiguaiensis, which is one of the stratigraphically oldest erythrosuchids and is known from a single partial skeleton from the lowermost Middle Triassic (lower Anisian) lower Ermaying Formation of Shaanxi Province, China. We provide a new differential diagnosis for Guchengosuchus shiguaiensis, and identify a series of autapomorphies relating to the morphologies of the skull roof and vertebrae. Incorporating updated anatomical information for Guchengosuchus into the most comprehensive morphological phylogenetic analysis available for early archosauromorphs recovers it as an early branching member of Erythrosuchidae, outside of the clade formed by Garjainia, Erythrosuchus, Chalishevia, and Shansisuchus. Fugusuchus hejiapanensis, from the uppermost Lower Triassic to lower Middle Triassic Heshanggou Formation of China, is recovered as the earliest branching member of Erythrosuchidae. [ABSTRACT FROM AUTHOR]

Prestosuchus chiniquensis is the most famous "rauisuchian" described by Friedrich von Huene, eight decades ago, and several specimens have been assigned to this taxon since then. In the present contribution, we provide the first detailed description of a complete and very well preserved skull (including the braincase) assigned to Prestosuchus chiniquensis from the Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence of southern Brazil. The detailed description of the skull of Prestosuchus chiniquensis, besides increasing the knowledge about this taxon, may help elucidate the taxonomic relationships of pseudosuchians even further, since most of the characters used in phylogenetic analyzes are cranial. The presence of the subnarial fenestra, a controvertial extra opening on the skull of "rauisuchians", is thoroughly discussed considering the evidence provided by this new specimen. We consider that the small slit-opening between the premaxilla and the maxilla in Prestosuchus chiniquensis, can not safely be considered a true fenestra, but indicates more likely the existence of some degree of cranial kinesis between these elements which can result in different relative positions of the bones after definitive burial and fossilization, so that the size and shape of this opening is taphonomically controlled. Complementarily, the digital reconstruction of its cranial endocast was developed both from the observation of the preserved braincase and from CT scan images, which resulted in obtaining the first endocast known for a "rauisuchian". The endocast of Prestosuchus chiniquensis exhibited some remarkable convergences with that of theropod dinosaurs, which could be a reflection of the similar niches they occupied, since "rauisuchians" were the top predators at the end of the Late Triassic, before the extinction of all non-crocodylomorph pseudosuchians. [ABSTRACT FROM AUTHOR]

The evolution and diversification of Triassic pseudosuchian lineages has been the subject of much interest and revision in the last couple of decades, fuelled by new and important discoveries, which have allowed for better-sampled phylogenetic analysis. In the present contribution, we add to this by describing a new taxon, Pagosvenator candelariensis gen. et sp. nov. for the Middle–Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence of southernmost Brazil. A comparative osteological analysis combined with a phylogenetic analysis supports its inclusion within the clade Erpetosuchidae and provides an insight into the phylogenetic relationship and evolutionary history of this clade, with two possibilities for the Erpetosuchidae relationship: as an early branch of pseudosuchians, being a sister group of Ornithosuchidae; or a closer relationship with the clade composed by Gracilisuchidae and Paracrodylomorpha with respect to Orntithosuchidae and Aetosauria. Additionally, the results presented and discussed here are of biostratigraphical importance, given that the taxon is from the Ladinian/Carnian age and would fill a temporal gap that exists within Erpetosuchidae between Parringtonia gracilis from the Anisian and Erpetosuchus from late the Carnian to Norian. Furthermore, it would be the first occurrence of a member of this clade in South America. [ABSTRACT FROM AUTHOR]

Calyptosuchus wellesi is a medium-sized desmatosuchian aetosaur common in Adamanian (early to middle Norian) age rocks from the Chinle Formation and Dockum Group of the Western United States. Known chiefly from osteoderms, this taxon has never been fully described and non-osteoderm material assigned to Calyptosuchus has been done so based on questionable criteria. Mapping of aetosaurian elements from the Placerias Quarry allows for the recognition of associated material providing support for referrals of non-osteoderm material. Furthermore, another previously undescribed specimen from the Chinle Formation of Arizona provides more details about this taxon. Presently Calyptosuchus lacks discrete autapomorphies, but can be distinguished from other aetosaurs based on a unique combination of characters supported by a phylogenetic analysis. Calyptosuchus is one of the most common aetosaurians in theWestern United States and an index taxon of the early Adamanian biozone. The name Calyptosuchus is retained and encouraged as the applicable genus name for the species wellesi rather than the often used Stagonolepis because assignments of taxa to multi-species genus names are problematic and in this case provides a proposed taxonomic relationship that cannot be unambiguously supported, even by phylogenetic analyses. Because of the inherent limitations of the fossil record, referral of specimens and species to species and genera respectively is an epistemological problem in vertebrate paleontology. [ABSTRACT FROM AUTHOR]

Vertebrates from the Triassic Period have broadly disparate tooth shapes and dentition patterns, the result of intense morphospace experimentation following the Permo-Triassic extinction. Here, we describe fragmentary tooth-bearing jaw elements of the rare Gondwanan Middle Triassic taxon Palacrodon that represent first occurrences from the Upper Triassic Chinle Formation in northeastern Arizona. These specimens come from two notably diverse macrovertebrate and microvertebrate assemblages, the "coprolite layer" horizon in Petrified Forest National Park, and the Placerias Quarry near St. Johns, Arizona. Palacrodon is diagnosed by the presence of acrodont maxillary and dentary dentition of labiolingually-widened, bulbous teeth, which are fused to one another mesiodistally, and are pyramidal in lateral view. We agree with previous workers and refer Palacrodon to Diapsida based on the presence of a posterior jugal spur and a quadrate that has a quadratojugal foramen and a concave posterior surface. Formerly known only from the Cynognathus Assemblage Zone in southern Africa and Antarctica, the presence of Palacrodon in the Norian of North America represents a temporal range extension of at least 15 million years and represents the first tetrapod genus known to be present in the Karoo Basin, Fremouw Formation, and the Upper Triassic of the southwestern United States. Range extensions such as this suggest that some vertebrate biostratigraphic hypotheses for the Triassic may be less robust than previously believed and subject to significant sampling biases. [ABSTRACT FROM AUTHOR]

Vertebrates from the Triassic Period have broadly disparate tooth shapes and dentition patterns, the result of intense morphospace experimentation following the Permo-Triassic extinction. Here, we describe fragmentary tooth-bearing jaw elements of the rare Gondwanan Middle Triassic taxon Palacrodon that represent first occurrences from the Upper Triassic Chinle Formation in northeastern Arizona. These specimens come from two notably diverse macrovertebrate and microvertebrate assemblages, the "coprolite layer" horizon in Petrified Forest National Park, and the Placerias Quarry near St. Johns, Arizona. Palacrodon is diagnosed by the presence of acrodont maxillary and dentary dentition of labiolingually-widened, bulbous teeth, which are fused to one another mesiodistally, and are pyramidal in lateral view. We agree with previous workers and refer Palacrodon to Diapsida based on the presence of a posterior jugal spur and a quadrate that has a quadratojugal foramen and a concave posterior surface. Formerly known only from the Cynognathus Assemblage Zone in southern Africa and Antarctica, the presence of Palacrodon in the Norian of North America represents a temporal range extension of at least 15 million years and represents the first tetrapod genus known to be present in the Karoo Basin, Fremouw Formation, and the Upper Triassic of the southwestern United States. Range extensions such as this suggest that some vertebrate biostratigraphic hypotheses for the Triassic may be less robust than previously believed and subject to significant sampling biases. [ABSTRACT FROM AUTHOR]

Osteoderms are common in most archosauriform lineages, including basal forms, such as doswelliids and proterochampsids. In this survey, osteoderms of the doswelliids Doswellia kaltenbachi and Vancleavea campi, and proterochampsid Chanaresuchus bonapartei are examined to infer their palaeobiology, such as histogenesis, age estimation at death, development of external sculpturing, and palaeoecology. Doswelliid osteoderms have a trilaminar structure: two cortices of compact bone (external and basal) that enclose an internal core of cancellous bone. In contrast, Chanaresuchus bonapartei osteoderms are composed of entirely compact bone. The external ornamentation of Doswellia kaltenbachi is primarily formed and maintained by preferential bone growth. Conversely, a complex pattern of resorption and redeposition process is inferred in Archeopelta arborensis and Tarjadia ruthae. Vancleavea campi exhibits the highest degree of variation among doswelliids in its histogenesis (metaplasia), density and arrangement of vascularization and lack of sculpturing. The relatively high degree of compactness in the osteoderms of all the examined taxa is congruent with an aquatic or semi-aquatic lifestyle. In general, the osteoderm histology of doswelliids more closely resembles that of phytosaurs and pseudosuchians than that of proterochampsids. [ABSTRACT FROM AUTHOR]

Osteoderms are common in most archosauriform lineages, including basal forms, such as doswelliids and proterochampsids. In this survey, osteoderms of the doswelliids Doswellia kaltenbachi and Vancleavea campi, and proterochampsid Chanaresuchus bonapartei are examined to infer their palaeobiology, such as histogenesis, age estimation at death, development of external sculpturing, and palaeoecology. Doswelliid osteoderms have a trilaminar structure: two cortices of compact bone (external and basal) that enclose an internal core of cancellous bone. In contrast, Chanaresuchus bonapartei osteoderms are composed of entirely compact bone. The external ornamentation of Doswellia kaltenbachi is primarily formed and maintained by preferential bone growth. Conversely, a complex pattern of resorption and redeposition process is inferred in Archeopelta arborensis and Tarjadia ruthae. Vancleavea campi exhibits the highest degree of variation among doswelliids in its histogenesis (metaplasia), density and arrangement of vascularization and lack of sculpturing. The relatively high degree of compactness in the osteoderms of all the examined taxa is congruent with an aquatic or semi-aquatic lifestyle. In general, the osteoderm histology of doswelliids more closely resembles that of phytosaurs and pseudosuchians than that of proterochampsids. [ABSTRACT FROM AUTHOR]

The so-called historical Polish discoveries of Triassic ‘dinosaurs’ have been repeatedly cited in papers and popular science books. Here, we re-evaluate each historical and purported Triassic dinosaur find from Poland. Additionaly, we describe several supposed ‘dinosaur’ bones collected by Polish geologists but only briefly mentioned: in regional geological journals, on collection labels, or in field notes. We attempt to assign all investigated specimens to the least inclusive taxon possible. Our revision indicates that part of this material represents non-dinosaur archosauromorph taxa. Most of the analysed specimens are fragmentary bones or isolated teeth and are indistinguishable from skeletal elements described from other well-known Triassic archosauromorph taxa. We conclude that fossils of dinosauriforms are present in the Upper Triassic of Silesia and Holy Cross Mountains. New analysis ofVelocipes guerichivon Huene, 1932 holotype specimen from Kocury shows that it is the proximal part of fibula of a medium-sized theropod (or even neotheropod). Formally undescribed part of dinosauriform limb bone from the Holy Cross Mountains andV.guerichifrom Silesia are the only identifiable dinosauromorph skeletal remains recognised in the Polish Triassic discovered prior to the description ofSilesaurus opolensisDzik, 2003 from the Upper Carnian of Krasiejów. [ABSTRACT FROM PUBLISHER]

Clevosauruswas a cosmopolitan Rhynchocephalia genus restricted to the Late Triassic and the Early Jurassic. In Brazil,C. brasiliensisis one of the most conspicuous species collected from the Candelária Sequence (RiograndiaAssemblage Zone, Norian age) of the Santa Maria Supersequence. Several jaws ofC. brasiliensisare housed in the Laboratório de Paleontologia de Vertebrados of the Instituto de Geociências-UFRGS. Some of these jaws bear a relatively small protuberant bony callus on the anterolateral margin of the dentary, evidenced by a different tissue pattern incorporating small pits and discrete grooves. This pattern closely resembles a common bone infection known in the mandible of the extantSphenodon punctatus. Although this similarity, the infection may be the result of two possible processes: as consequence of orthal jaw shearing movements during feeding at the moments that the dentary impacts with the enlarged premaxillary tooth or due to injuries produced after fights between conspecific individuals (as is the case forS. punctatus). If the second hypothesis is correct, the same pathological processes probably occurred in the Late TriassicC. brasiliensisindicating that similar ethological conditions were already present at the beginning of the Mesozoic, during the initial radiation of the lepidosaurian clade. [ABSTRACT FROM PUBLISHER]

The present work provides a detailed lithological map of the western part of the Satpura basin around Sohagpur and reports the presence of new archosauromorph fossil bones from that region. The study area is dominated by the Bagra Formation along with a narrow patch of the underlying upper part of the Denwa Formation. The lower Denwa and the underlying Pachmarhi formations are absent here. The presence of the Pachmarhi Formation, as a tongue shaped area, as mapped by Crookshank (1936) is discarded in this study on the basis of lithology and petrographic analyses, instead the presence of the Bagra Formation is suggested in this area. A comparison of the lithologies and the vertebrate faunas of the upper Gondwana formations between eastern and western part of the basin has been carried out for the first time. The comparison indicates that the Denwa Formation present in the western sector represents only the topmost part of the formation while the complete succession of Denwa is preserved in the eastern sector. The Bagra Formation in the western sector documents the presence of sheet-like sandstone bodies unlike the eastern part. The vertebrate fauna of the eastern part is dominated by temnospondyl amphibians while that of the western part is dominated by archosauromorph. The vertebrate fossils of upper part of Denwa Formation, found from similar lithologies in west and east though, have differences in the amount of transportation before their burial. [ABSTRACT FROM AUTHOR]

The Triassic plant macrofossils of Poland are very poorly known. There are few Triassic rock exposures here, they contain very few plant specimens, there is little scientific interest in the subject, and the rare plant remains found in drill cores are of low stratigraphical significance. The Lower Triassic macroflora is surprisingly poorer taxonomically than coeval European floras, and only single specimens have been found. The flora of the Middle Triassic is even poorer as a result of the Muschelkalk sea transgression. Only the Upper Triassic floras contain many specimens and taxa. The Upper Triassic macrofloras from Polish territory are well known since the early 19th century. Pioneering descriptions of these floras were given by Goeppert and Raciborski. From the Polish Triassic, the seed fern Lepidopteris ottonis (index species for the Rhaetian stage) and Neocalamites lehmannianus (sphenopsid species typical of almost all European Upper Triassic and Lower Jurassic floras) were described for the first time ever. In the 20th century only single specimens were described from outcrops and drill cores. Barbacka revised Lepidopteris ottonis specimens from old collections and described some new material. Palynological research on Triassic strata in Poland intensified from the 1970s on. That work has produced spore-pollen and megaspore zonations for Triassic strata in Poland, but the correlation of the dispersed spores and pollen grains with their parent plants is low. The Polish Triassic flora is comprised of ferns, lycopsids, sphenopsids, cycads, bennettitaleans, ginkgoaleans and conifers. This flora is taxonomically poorer than equally old and geographically close European floras. All available data about Polish Triassic plants fossils are critically summarised in this paper for the first time. The biostratigraphical and lithostratigraphical correlations of Polish Triassic floras with other European Triassic floras are outlined. New macrofloral assemblages for the Lower and Middle Triassic and macrofloral assemblage zones for the Upper Triassic are proposed for Poland. Recent new finds of taxonomically rich, abundant and well-preserved floras accompanying vertebrate remains in Silesia provide an opportunity for comprehensive research on Polish Triassic floras. This should improve our perception of their taxonomy and allow them to be described in evolutionary and palaeoecological contexts. [ABSTRACT FROM AUTHOR]

Numerous well-preserved skeletal remains of a distinctive armoured archosauriform reptile from the Lower Keuper (Erfurt Formation; Middle Triassic: Ladinian: Longobardian) of Baden-Württemberg (Germany) represent a new taxon,Jaxtasuchus salomonigen. et sp. nov. The dermal armour ofJaxtasuchuscomprises transverse rows of four rectangular osteoderms each in the cervical, dorsal and caudal regions, with the individual plates closely resembling those ofDoswellia kaltenbachifrom Carnian strata in North America. The long and low maxilla ofJaxtasuchusheld at least 15 teeth. The labial and lingual surfaces of the tall, only slightly recurved crowns of the maxillary teeth bear distinct vertical ridges and smooth mesial and distal carinae. The cervical region of the vertebral column is long. Phylogenetic analysis placesJaxtasuchusas the sister taxon toDoswelliain DoswelliidaesensuDesojoet al. (2011). Doswelliidae is diagnosed by the coarsely reticulate, incised ornamentation of osteoderms composed of central regular pits of subequal size and contour, and a mostly smooth anterior articular lamina on each osteoderm. The discovery ofJaxtasuchusconfirms that Doswelliidae had a wide palaeogeographical distribution during the latter half of the Triassic. http://www.zoobank.org/urn:lsid:zoobank.org:pub:4A400628-07F3-4D1B-9CA8-336C379721FA [ABSTRACT FROM PUBLISHER]

Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook-like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla-maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic ( Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic. [ABSTRACT FROM AUTHOR]

The current work attempts to address a century old problem regarding the stratigraphic disposition of the Upper Gondwana succession of the Rewa basin based on geological mapping and litholog preparation along well exposed transects. The proposed Upper Gondwana stratigraphy of the Rewa basin comprises a continuous and thick package of Triassic sediments unconformably overlain by the Jurassic Parsora Formation. The Triassic succession consists of a basal Pali Formation, an intermediate and newly designated Karki Formation and the overlying mud-dominant Tiki Formation. These formations are well defined based on physical attributes such as lithology, textures and sedimentary structures, and are easily distinguishable in the field. Based on stratigraphic correlation and fossil content, a Lower-Middle Triassic age has been assigned for the Pali and Karki formations, while the Tiki Formation is Upper Triassic (Carnian) in age. Preliminary observations based on lithological characteristics, sand body geometry and sand: mud ratios suggest that within a fluvial setting there were considerable changes in environments of deposition through time, especially during Triassic to Jurassic transition. [ABSTRACT FROM AUTHOR]

Disarticulated material from the Late Triassic Timezgadiouine Formation in the Argana Basin of Morocco represents a new taxon of silesaurid dinosauromorph, Diodorus scytobrachion gen. et sp. nov. D. scytobrachion can be distinguished from other silesaurids by the presence of anteriorly-canted teeth that decrease in size towards the anterior end of the dentary and a distinct lateral ridge running parallel to the dentary alveolar margin. In a phylogenetic analysis, D. scytobrachion is recovered as the sister-taxon to the Brazilian Sacisaurus agudoensis, nested deep within Silesauridae. This new taxon provides further evidence of a near-cosmopolitan range for basal dinosauriforms in the Late Triassic and further demonstrates the disparity of dental morphologies within Silesauridae. [ABSTRACT FROM AUTHOR]

Brachychirotherium is the common ichnogenus of Late Triassic chirothere footprints well known from western Europe, North America, Argentina and South Africa. Although it has long been agreed by most workers that the trackmaker of Brachychirotherium was a derived crurotarsan archosaur, the trackmaker has been identified as either a rauisuchian or an aetosaur, and some workers attribute it to a primitive crocodylomorph (sphenosuchian). New knowledge of the osteology of the manus and pes of a large aetosaur, Typothorax coccinarum, indicates a close correspondence between the manus and pes structure of aetosaurs and the morphology of Brachychirotherium. Furthermore, functional analysis of complete skeletons indicates aetosaurs plausibly placed their feet in the narrow gauge, nearly the overstepped walk characteristic of Brachychirotherium. Brachychirotherium and aetosaurs have matched distributions, that is, they were Pangea-wide during the Late Triassic. The manus and pes morphology of rauisuchians and early crocodylomorphs (sphenosuchians) deviate from Brachychirotherium footprint morphology in key features, thus excluding their identification as trackmakers. Aetosaurs made Brachychirotherium footprints. [ABSTRACT FROM PUBLISHER]

Venom delivery systems occur in a wide range of extant and fossil vertebrates and are primarily based on oral adaptations. Teeth range from unmodified (Komodo dragons) to highly specialized fangs similar to hypodermic needles (protero- and solenoglyphous snakes). Developmental biologists have documented evidence for an infolding pathway of fang evolution, where the groove folds over to create the more derived condition. However, the oldest known members of venomous clades retain the same condition as their extant relatives, resulting in no fossil evidence for the transition. Based on a comparison of previously known specimens with newly discovered teeth from North Carolina, we describe a new species of the Late Triassic archosauriform Uatchitodon and provide detailed analyses that provide evidence for both venom conduction and document a complete structural series from shallow grooves to fully enclosed tubular canals. While known only from teeth, Uatchitodon is highly diagnostic in possessing compound serrations and for having two venom canals on each tooth in the dentition. Further, although not a snake, Uatchitodon sheds light on the evolutionary trajectory of venom delivery systems in amniotes and provide solid evidence for venom conduction in archosaur-line diapsids. [ABSTRACT FROM AUTHOR]

The rise of archosaurs during the Triassic and Early Jurassic has been treated as a classic example of an evolutionary radiation in the fossil record. This paper reviews published studies and provides new data on archosaur lineage origination, diversity and lineage evolution, morphological disparity, rates of morphological character change, and faunal abundance during the Triassic???Early Jurassic. The fundamental archosaur lineages originated early in the Triassic, in concert with the highest rates of character change. Disparity and diversity peaked later, during the Norian, but the most significant increase in disparity occurred before maximum diversity. Archosaurs were rare components of Early???Middle Triassic faunas, but were more abundant in the Late Triassic and pre-eminent globally by the Early Jurassic. The archosaur radiation was a drawn-out event and major components such as diversity and abundance were discordant from each other. Crurotarsans (crocodile-line archosaurs) were more disparate, diverse, and abundant than avemetatarsalians (bird-line archosaurs, including dinosaurs) during the Late Triassic, but these roles were reversed in the Early Jurassic. There is no strong evidence that dinosaurs outcompeted or gradually eclipsed crurotarsans during the Late Triassic. Instead, crurotarsan diversity decreased precipitously by the end-Triassic extinction, which helped usher in the age of dinosaurian dominance. [ABSTRACT FROM PUBLISHER]

Triassic tetrapods are of key importance in understanding their evolutionary history, because several tetrapod clades, including most of their modern lineages, first appeared or experienced their initial evolutionary radiation during this Period. In order to test previous palaeobiogeographical hypotheses of Triassic tetrapod faunas, tree reconciliation analyses (TRA) were performed with the aim of recovering biogeographical patterns based on phylogenetic signals provided by a composite tree of Middle and Late Triassic tetrapods. The TRA found significant evidence for the presence of different palaeobiogeographical patterns during the analysed time spans. First, a Pangaean distribution is observed during the Middle Triassic, in which several cosmopolitan tetrapod groups are found. During the early Late Triassic a strongly palaeolatitudinally influenced pattern is recovered, with some tetrapod lineages restricted to palaeolatitudinal belts. During the latest Triassic, Gondwanan territories were more closely related to each other than to Laurasian ones, with a distinct tetrapod fauna at low palaeolatitudes. Finally, more than 75 per cent of the cladogenetic events recorded in the tetrapod phylogeny occurred as sympatric splits or within-area vicariance, indicating that evolutionary processes at the regional level were the main drivers in the radiation of Middle and Late Triassic tetrapods and the early evolution of several modern tetrapod lineages. [ABSTRACT FROM AUTHOR]

Crown group Archosauria, which includes birds, dinosaurs, crocodylomorphs, and several extinct Mesozoic groups, is a primary division of the vertebrate tree of life. However, the higher-level phylogenetic relationships within Archosauria are poorly resolved and controversial, despite years of study. The phylogeny of crocodile-line archosaurs (Crurotarsi) is particularly contentious, and has been plagued by problematic taxon and character sampling. Recent discoveries and renewed focus on archosaur anatomy enable the compilation of a new dataset, which assimilates and standardizes character data pertinent to higher-level archosaur phylogeny, and is scored across the largest group of taxa yet analysed. This dataset includes 47 new characters (25% of total) and eight taxa that have yet to be included in an analysis, and total taxonomic sampling is more than twice that of any previous study. This analysis produces a well-resolved phylogeny, which recovers mostly traditional relationships within Avemetatarsalia, places Phytosauria as a basal crurotarsan clade, finds a close relationship between Aetosauria and Crocodylomorpha, and recovers a monophyletic Rauisuchia comprised of two major subclades. Support values are low, suggesting rampant homoplasy and missing data within Archosauria, but the phylogeny is highly congruent with stratigraphy. Comparison with alternative analyses identifies numerous scoring differences, but indicates that character sampling is the main source of incongruence. The phylogeny implies major missing lineages in the Early Triassic and may support a Carnian-Norian extinction event. [ABSTRACT FROM AUTHOR]

The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as “all descendants of the most recent common ancestor of birds and Triceratops”. Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and Spondylosoma absconditum. The identification of dinosaur apomorphies is jeopardized by the incompleteness of skeletal remains attributed to most basal dinosauromorphs, the skulls and forelimbs of which are particularly poorly known. Nonetheless, Dinosauria can be diagnosed by a suite of derived traits, most of which are related to the anatomy of the pelvic girdle and limb. Some of these are connected to the acquisition of a fully erect bipedal gait, which has been traditionally suggested to represent a key adaptation that allowed, or even promoted, dinosaur radiation during Late Triassic times. Yet, contrary to the classical “competitive” models, dinosaurs did not gradually replace other terrestrial tetrapods over the Late Triassic. In fact, the radiation of the group comprises at least three landmark moments, separated by controversial (Carnian-Norian, Triassic-Jurassic) extinction events. These are mainly characterized by early diversification in Carnian times, a Norian increase in diversity and (especially) abundance, and the occupation of new niches from the Early Jurassic onwards. Dinosaurs arose from fully bipedal ancestors, the diet of which may have been carnivorous or omnivorous. Whereas the oldest dinosaurs were geographically restricted to south Pangea, including rare ornithischians and more abundant basal members of the saurischian lineage, the group achieved a nearly global distribution by the latest Triassic, especially with the radiation of saurischian groups such as “prosauropods” and coelophysoids. [ABSTRACT FROM AUTHOR]

Definitive criteria for distinguishing gastroliths from sedimentary clasts are lacking for many depositional settings, and many reported occurrences of gastroliths either cannot be verified or have been refuted. We discuss four occurrences of gastrolith-like stones (category 6 exoliths) not found within skeletal remains from the Upper Triassic Bull Run Formation of northern Virginia, USA. Despite their lack of obvious skeletal association, the most parsimonious explanation for several characteristics of these stones is their prolonged residence in the gastric mills of large animals. These characteristics include 1) typical gastrolith microscopic surface texture, 2) evidence of pervasive surface wear on many of these stones that has secondarily removed variable amounts of thick weathering rinds typically found on these stones, and 3) a width/length-ratio modal peak for these stones that is more strongly developed than in any population of fluvial or fanglomerate stones of any age found in this region. When taken together, these properties of the stones can be explained most parsimoniously by animal ingestion and gastric-mill abrasion. The size of these stones indicates the animals that swallowed them were large, and the best candidate is a prosauropod dinosaur, possibly an ancestor of the Early Jurassic gastrolith-producing prosauropod Massospondylus or Ammosaurus. Skeletal evidence for Upper Triassic prosauropods is lacking in the Newark Supergroup basins; footprints (Agrestipus hottoni and Eubrontes isp.) from the Bull Run Formation in the Culpeper basin previously ascribed to prosauropods are now known to be underprints (Brachychirotherium parvum) of an aetosaur and underprints (Kayentapus minor) of a ceratosaur. The absence of prosauropod skeletal remains or footprints in all but the uppermost (upper Rhaetian) Triassic rocks of the Newark Supergroup is puzzling because prosauropod remains are abundant elsewhere in the world in Upper Triassic (Carnian, Norian, and lower Rhaetian) continental strata. The apparent scarcity of prosauropods in Upper Triassic strata of the Newark Supergroup is interpreted as an artifact of ecological partitioning, created by the habitat range and dietary preferences of phytosaurs and by the preservational biases at that time within the lithofacies of the Newark Supergroup basins. [ABSTRACT FROM AUTHOR]

The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re-evaluation of saurischian and theropod synapomorphies. Here, we re-evaluate each purported Triassic dinosaur from North America on a specimen by specimen basis using an apomorphy-based approach. We attempt to assign specimens to the most exclusive taxon possible. Our revision of purported Late Triassic dinosaur material from North America indicates that dinosaurs were rarer and less diverse in these strata than previously thought. This analysis concludes that non-dinosaurian dinosauriforms were present in North America in the Late Triassic. Most of the proposed theropod specimens are fragmentary and/or indistinguishable from corresponding elements in the only well-known Triassic theropod of North America, Coelophysis bauri. No Triassic material from North America can be assigned to Sauropodomorpha, because none of the purported 'prosauropod' material is diagnostic. Recent discovery of the skull and skeleton of Revueltosaurus callenderi from Arizona shows that it is a pseudosuchian archosaur, not an ornithischian dinosaur. As a result, other purported North American ornithischian teeth cannot be assigned to the Ornithischia and therefore, there are no confirmed North American Triassic ornithischians. Non-tetanuran theropods and possible basal saurischians are the only identifiable dinosaurs recognised in North America until the beginning of the Jurassic Period. [ABSTRACT FROM AUTHOR]

Ornithischian dinosaurs are one of the most taxonomically diverse dinosaur clades during the Mesozoic, yet their origin and early diversification remain virtually unknown. In recent years, several new Triassic ornithischian taxa have been proposed, mostly based upon isolated teeth. New discoveries of skeletal material of some of these tooth taxa indicate that these teeth can no longer be assigned to the Ornithischia using unambiguous synapomorphies. The Triassic record of ornithischian dinosaurs now comprises only three probable occurrences: Pisanosaurus and an unnamed heterodontosaurid from Argentina, and an unnamed specimen from the uppermost Triassic of South Africa. This revised Triassic record suggests that ornithischians were not very diverse or abundant through the Triassic, and there are large gaps in the Triassic ornithischian fossil record. Moreover, traditional living analogues for interpreting the feeding ecology of early ornithischians from their tooth morphology are generally inappropriate, and "herbivorous" archosaur teeth such as those found in early ornithischians are not necessarily diagnostic of herbivorous feeding. [ABSTRACT FROM AUTHOR]

Well-preserved cranial remains of a small sphenodontian lepidosaur from the Upper Triassic Caturrita Formation of Rio Grande do Sul, Brazil, are the first record of the genus Clevosaurus Swinton, 1939 from South America. They represent a new species, Clevosaurus brasiliensis, which is distinguished by a very short antorbital region of the skull (corresponding to about 20 per cent of skull length) and the presence of teeth in addition to two longitudinal rows on the pterygoid. C. brasiliensis most closely resembles C. bairdi from the Lower Jurassic of Nova Scotia (Canada) and C. mcgilli from the Lower Jurassic of Yunnan (China). The discovery of Clevosaurus in the Upper Triassic of southern Brazil provides a significant range extension of this widely distributed sphenodontian genus. Along with other recent finds, it also suggests that there may have been less biotic provincialism among terrestrial vertebrates during the Late Triassic than has previously been assumed. [ABSTRACT FROM AUTHOR]

Geographical Information Systems (GIS) have been applied extensively to analyse spatial data relating to varied environmental issues, but have not so far been used to address biostratigraphical or macroevolutionary questions over extended spatial and temporal scales. Here, we use GIS techniques to test the stability, validity and utility of proposed Middle and Late Triassic 'Land Vertebrate Faunachrons' (LVFs), a global biostratigraphical framework based upon terrestrial/freshwater tetrapod occurrences. A database of tetrapod and megafloral localities was constructed for North America and Western Europe that also incorporated information on relevant palaeoenvironmental variables. This database was subjected to various spatial analysis techniques. Our GIS analysis found support at a global level for Eocyclotosaurus as an Anisian index taxon and probably Aetosaurus as a Norian indicator. Other tetrapod taxa are useful biostratigraphical/biochronological markers on a regional basis, such as Longosuchus and Doswellia for Late Carnian time. Other potential index fossils are hampered, however, by taxonomic instability (Mastodonsaurus, Metoposaurus, Typothorax, Paleorhinus, Pseudopalatus, Redondasaurus, Redondasuchus) and/or are not clearly restricted in temporal distribution (Paleorhinus, Angistorhinus, Stagonolepis, Metoposaurus and Rutiodon). This leads to instability in LVF diagnosis. We found only in the western Northern Hemisphere is there some evidence for an Anisian-Ladinian biochronological unit amalgamating the Perovkan and Berdyankian LVFs, and a possible late Carnian unit integrating the Otischalkian and Adamanian. Megaplants are generally not useful for biostratigraphical correlation in the Middle and Upper Triassic of the study area, but there is some evidence for a Carnian-age floral assemblage that corresponds to the combined Otischalkian and Adamanian LVFs, Environmental biases do not appear to strongly affect the spatial distribution of either the tetrapods or megaplants that have been proposed as index taxa in biostratigraphical schemes, though several examples of apparent environmental bias were detected by the analysis. Consequently. we argue that further revision and refinement of Middle and Late Triassic LVFs is needed before they can be used to support global or multi-regional biostratigraphical correlations. Caution should therefore be exercised when using the current scheme as a platform for macroevolutionary or palaeoecological hypotheses. Finally, this study demonstrates the potential of GIS as a powerful tool for tackling palaeontological questions over extended timescales. [ABSTRACT FROM AUTHOR]

The marine reptileEndennasaurusfrom the Upper Triassic Zorzino Limestone of northern Italy is redescribed and reassessed. New details of the skull and postcranial skeleton are revealed, confirming the attribution of this genus to the diapsid reptile clade Thalattosauriformes. Phylogenetic analysis suggests thatEndennasauruswas related to the European genusAskeptosaurusand the ChineseAnshunsaurus. Despite a rather conservative postcranial morphology,Endennasaurusclearly occupied a highly specialized dietary niche as it combined a slender tapering premaxillary rostrum with a complete absence of either marginal or palatal teeth. [ABSTRACT FROM AUTHOR]