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Correlations between continental sequences within the Karoo-aged basins of southern and eastern Africa are difficult due to the dearth of shared index fossils and a lack of radioisotopic dates for key formations. Here we describe four sites along the southeastern shoreline of Lake Kariba, Zimbabwe, within the Mid-Zambezi Basin, that yield material of phytosaurs (Archosauromorpha: Phytosauria) from within the informal Tashinga Formation (Upper Karoo Group). These phytosaur remains are the first to be recovered from sub-Saharan mainland Africa, representing a major geographic range extension for this group into high southern latitudes. Furthermore, an LA-ICPMS maximum depositional age of 209.2 ± 4.5 Ma (late Norian/early Rhaetian) derived from detrital zircons provides the first absolute age estimate for any of these sites. The phytosaurs are associated with lungfish and metoposaurid amphibians, forming part of a terrestrial-aquatic dominated biota, a previously undocumented biome from the Late Triassic of southern Africa.

A monotaxic bonebed containing numerous phytosaur specimens is reported from the Upper Triassic Tiki Formation of India. The comprehensive minimum number of individuals is estimated to be 21, which includes multiple juveniles and subadults, and only a few adults. Such intraspecific aggregation of juvenile-dominated phytosaurs is explained here by parental care and juveniles living in cohorts, as are evident from extant phylogenetic bracketing of either lepidosaurs or crocodiles and birds. The cause of this mass death is probably disease related, after which the carcasses bloated, floated, and disarticulated at the site of death, resulting in an autochthonous assemblage. The carcasses remained submerged under shallow, slow-moving or standing water for a prolonged time and later were subaerially exposed after the recession of water. Subsequently, flooding events resulted in their burial under the overbank fines. Comparison of biostratinomic variables with those of a rhynchosaur-dominated bonebed recovered previously from the same stratigraphic horizon showed distinct differences in their causes of death and fossilization pathways. The latter may be attributed to their habitat differences because the phytosaurs lived in the low-lying areas or ponds and the rhynchosaurs resided on relatively higher and drier areas of the Tiki floodplain.

Herein we describe phytosaurs from thin fluvial overbank sandstones of the Upper Triassic Malmros Klint Formation of the Fleming Fjord Group (central East Greenland). The new sample includes more than 150 disarticulated bones and teeth from small to large specimens belonging to at least four individuals. The fossils mostly consist of teeth and postcranial elements and permit the recognition of a new species of Mystriosuchus, M. alleroq, diagnosed by an L-shaped quadratojugal whose anterior suture trends anterodorsally and a tripartite degree of heterodonty. Humeral diaphyseal histology of one specimen reveals a fairly compact cortex that surrounds a cancellous medullary region followed by a remodeling zone containing scattered secondary osteons. Primary bone tissue is parallel-fibred with a moderate to low vascular density. The cortex is cyclically interrupted by distinct growth marks indicating a seasonal environment. A change in growth rate from moderate to low is documented within the outer cortex, indicating that at least this individual was close to somatic maturity. Mystriosuchus has formerly been known as an exclusively European taxon. The new findings support the European faunal influence in East Greenland during the Late Triassic inferred from other taxa such as temnospondyls and archosaurs. The mid-late Norian age of European Mystriosuchus suggests an additional age constraint for the vertebrate-bearing portion of the Malmros Klint Formation.

Following the end-Permian extinction, terrestrial vertebrate diversity recovered by the Middle Triassic, and that diversity was now dominated by reptiles. However, those reptilian clades, including archosaurs and their closest relatives, are not commonly found until ~30 million years post-extinction in Late Triassic deposits despite time-calibrated phylogenetic analyses predicting an Early Triassic divergence for those clades. One of these groups from the Late Triassic, Phytosauria, is well known from a near-Pangean distribution, and this easily recognized clade bears an elongated rostrum with posteriorly retracted nares and numerous postcranial synapomorphies that are unique compared with all other contemporary reptiles. Here, we recognize the exquisitely preserved, nearly complete skeleton of Diandongosuchus fuyuanensis from the Middle Triassic of China as the oldest and basalmost phytosaur. The Middle Triassic age and lack of the characteristically-elongated rostrum fill a critical morphological and temporal gap in phytosaur evolution, indicating that the characteristic elongated rostrum of phytosaurs appeared subsequent to cranial and postcranial modifications associated with enhanced prey capture, predating that general trend of morphological evolution observed within Crocodyliformes. Additionally, Diandongosuchus supports that the clade was present across Pangea, suggesting early ecosystem exploration for Archosauriformes through nearshore environments and leading to ease of dispersal across the Tethys.

Many recent studies have detailed the morphology of archosaurian endocrania. However, the outgroup to Archosauria, Phytosauria, has yet to be studied with modern techniques that would allow reconstruction of their internal anatomy. Pseudopalatus mccauleyi is a derived phytosaur from the Upper Triassic Chinle Formation, Arizona. A skull of P. mccauleyi, USNM 15839, was imaged using computed tomography in order to create the first high-quality, digitally reconstructed phytosaur endocast. Pseudopalatus mccauleyi exhibits overall endocast morphology that is similar to that of an extant crocodylian. These clades, phytosaurs and extant crocodylians, exhibit convergent Bauplane and similar inferred ecologies. A notable difference between the endocasts of the two clades is a considerable dural expansion in P. mccauleyi that denotes a large pineal body. This expansion, and the overall morphology of the endocast, is consistent with the historic endocranial reconstructions of the phytosaurs Pseudopalatus bu...

The Triassic was first defined based on the characteristic three-fold sequence of rocks that crops out across much of Europe, and many of the first records of Triassic dinosaurs, crocodile-line arc...

A new phytosaur taxon from Petrified Forest National Park, Arizona, is here described based on cranial material from a single individual. This specimen previously was included in an extensive phylogenetic analysis, and it was found to possess a combination of character states that differs from all known phytosaur taxa in addition to two autapomorphies within the braincase and an autapomorphy of the mandible. The new taxon adds to the taxonomic diversity recognized from the Sonsela Member of the Chinle Formation. The continued increase in phytosaur diversity emphasizes the need to more accurately characterize and identify taxa within a phylogenetic systematic context in order to produce a more refined signal for biostratigraphic correlations, biochronologic inferences, and faunal dynamics during the Late Triassic.

Leptosuchus Case, 1922 (Reptilia: Phytosauria) from the Late Triassic of the American West is represented by many specimens. Here, I present complete morphological descriptions of the skull material of a new taxon from the Sonsela Member (Chinle Formation) of Petrified Forest National Park, Arizona, with the first rigorous phylogenetic analysis focused on the interrelationships of Leptosuchus. The new taxon is recovered as the sister taxon to Pseudopalatinae. It possesses one unambiguous synapomorphy (the ‘septomaxillae’ form part of the lateral borders of the nares) and shares the presence of a subsidiary opisthotic process with Pseudopalatinae. The new taxon does not fall within the restricted clade Leptosuchus. In my analysis, the previously proposed, but undemonstrated, sister taxon relationship between Angistorhinus and Rutiodon is not supported, Paleorhinus is recovered as paraphyletic, and a subset of taxa traditionally included within Leptosuchus are found to be more closely related to Pseudopalatinae, rendering Leptosuchus paraphyletic. ‘Leptosuchus’adamanensis emerges as sister taxon to Smilosuchus gregorii and is here referred to as Smilosuchus adamanensis nov. comb., and ‘Machaeroprosopus’lithodendrorum is also transferred to Smilosuchus lithodendrorum nov. comb. Documentation of the variation present within Phytosauria, and specifically within Leptosuchus sensu lato, demonstrates higher diversity within Phytosauria than previously appreciated and places the character states previously proposed for Pseudopalatinae into a broader context of shared characters.

Mystriosuchus westphali is based on a large, well-preserved cranium and a snout fragment from the Stubensandstein (Norian) of south-west Germany. The hypodigm is redescribed and new or poorly known cranial structures in phytosaurs are discussed. For the first time, the presence of a premaxillary crest is substantiated in a phytosaur. The type specimen shows a supernumerary occipital element (=‘tabular’) that is probably fused to the parietal in other phytosaurs, and an orbitosphenoid. A computerised parsimony analysis confirms the hypothesis that Mystriosuchus is nested within Pseudopalatinae, the most derived clade of phytosaurs, and thus does not fall within basal phytosaurs. Mystriosuchus is characterised by five unique features (slit-like interpremaxillary fossa, triangular cross-section of the postorbito-squamosal bar, strongly reduced posttemporal fenestra, and two features of the cranial sculpture), plus eight synapomorphies that also occur in some more distantly related taxa. Mystriosuchus westphali is diagnosed by, among other apomorphies, a distinct premaxillary crest, a squamosal-proo¨tic contact, absence of a posterior process of the squamosal, and a slit-like posttemporal fenestra. The type species Mystriosuchus planirostris shows, most significantly, the naris facing forward anteriorly and upward posteriorly, and the longest rostrum and the highest degree of depression of the supratemporal opening in any phytosaur. Mystriosuchus exemplifies a common pattern in phytosaurids in being a genus that includes a gracile, elongated, slender-snouted and a more robust species with a broader, often crested snout. This study demonstrates that a detailed analysis of the cranial anatomy and the rigorous application of cladistic principles to identified character states help to clarify current inconsistencies in the taxonomy and nomenclature of phytosaurs.

Pathologies in the skeleton of phytosaurs, extinct archosauriform reptiles restricted to the Late Triassic, have only been rarely described. The only known postcranial pathologies of a phytosaur are two pairs of fused vertebrae of "Angistorhinopsis ruetimeyeri" from Halberstadt, Germany, as initially described by the paleontologist Friedrich von Huene. These pathologic vertebrae are redescribed in more detail in this study in the light of modern paleopathologic methods. Four different pathologic observations can be made in the vertebral column of this individual: 1) fusion of two thoracic vertebral bodies by new bone formation within the synovial membrane and articular capsule of the intervertebral joint; 2) fusion and conspicuous antero-posterior shortening of last presacral and first sacral vertebral bodies; 3) destruction and erosion of the anterior articular surface of the last presacral vertebra; and 4) a smooth depression on the ventral surface of the fused last presacral and first sacral vertebral bodies. Observations 1-3 can most plausibly and parsimoniously be attributed to one disease: spondyloarthropathy, an aseptic inflammatory process in which affected vertebrae show typical types of reactive new bone formation and erosion of subchondral bone. The kind of vertebral shortening present in the fused lumbosacral vertebrae suggests that the phytosaur acquired this disease in its early life. Observation 4, the smooth ventral depression in the fused lumbosacral vertebrae, is most probably not connected to the spondyloarthropathy, and can be regarded as a separate abnormality. It remains of uncertain origin, but may be the result of pressure, perhaps caused by a benign mass such as an aneurysm or cyst of unknown type. Reports of spondyloarthropathy in Paleozoic and Mesozoic reptiles are still exceptional, and our report of spondyloarthropathy in fossil material from Halberstadt is the first unequivocal occurrence of this disease in a Triassic tetrapod and in a phytosaur.

“Zanclodon”arenaceus has been suggested to represent the oldest reliably dated phytosaur. The type and only specimen, a mandibular fragment of an archosaur from the Schilfsandstein (Carnian; Late Triassic) of Southwest Germany, is described in detail for the first time. “Z.”arenaceus is characterized by a great elongation of the mandible and symphysis, and labiolingually flattened, serrated teeth, a combination that is so far unique among Triassic archosaurs. The previous assignment to the enigmatic reptilian genusZanclodon is unsubstantiated. “Z.”arenaceus shares with Phytosauria both these mandibular characters, but differs in numerous other characters, including most of the autapomorphic mandibular and dental features of Phytosauria. Thus, “Z.”arenaceus is not a phytosaur as currently defined. A cladistic analysis identified “Z.”arenaceus as the sister-taxon of Phytosauria, but because of the limited data available and numerous homoplasies that occur among mandibular characters of archosaurs a closer relationship with other archosaur taxa is a reasonable alternative. It seems unjustified to redefine Phytosauria, or to propose a more inclusive taxon to include “Z.”arenaceus, and therefore the species is assessed as Archosauriaincertae sedis.

The holotype and only specimen of Paleorhinus (= Arganarhinus) magnoculus is most likely a juvenile, as demonstrated by absolute size and skull proportions such as large orbits, a short snout and a narrow rostrum in comparison with other primitive (non-phytosaurid) phytosaurs. The specimen is the most complete juvenile phytosaur known, and may shed light on the poorly known ontogenetic development of phytosaurs. On the basis of the data available at present, P. magnoculus, and therefore Arganarhinus, cannot be regarded as valid taxa.

The dentition of Nicrosaurus kapffi, a phytosaur from the Norian of central Europe, consists of three distinct dental sets in the upper jaw, and two in the mandible. Dental sets are defined by: (1) gradual, linear transformations of dental characters within an array that results in characteristic end members; and (2) the position of each array within the jaws. The tip-of-snout set in the upper jaw comprises mainly the large fang-like anteriormost teeth. In the premaxilla set, the teeth grade from a conical, unspecialized form anteriorly to high, D-shaped and bicarinate teeth posteriorly. In the maxilla set the teeth grade from stout, conical, unspecialized forms anteriorly to triangular forms with expanded flanges posteriorly. The tip-of-mandible and the dentary set correspond to the tip-of-snout, and to an elongated maxilla set, respectively, but were studied in less detail. The presence of tripartite and bipartite dentitions (three versus two dental sets in the upper jaw) is suggested as a crit...

The red arkosic sandstones of the Cenger Formation, in the allochthonous units of the Lycian Taurus (western Turkey), which had already yielded a small ichthyofauna, have yielded fragmentary remains (teeth, jaw fragments, vertebrae) of archosaurian reptiles. Among these, phytosaur remains can be recognised; they are too incomplete to warrant an accurate identification, but they do provide biostratigraphical data, since they indicate a Late Triassic age. The reptile remains from the Cenger Formation thus confirm the stratigraphical conclusions previously drawn from the study of lungfishes, and increase our knowledge of the geographical distribution of Gondwanan phytosaurs.

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We describe here new Late Triassic haramiyidan mammaliaform and reptile fossils from near the classic ‘Microlestes’ Quarry’ at Holwell, Somerset, U.K., where Charles Moore discovered a huge collection of microvertebrates in the 1850s. Moore’s discoveries included the haramiyid Thomasia (formerly ‘Microlestes’ and Microcleptes) for which he achieved worldwide fame. Subsequently, despite much fossicking by researchers at Holwell, few new identifiable specimens of mammaliamorphs and lepidosaurs have been recorded and these were by Kuhne in 1939. The new finds described here from a bedded sequence, not from a fissure, add significantly to our knowledge of the Holwell tetrapods and to the Rhaetian terrestrial faunas of the SW U.K. Our discovery of haramiyidan teeth includes a previously unknown type of Theroteinus, a genus not previously recorded from outside of the St-Nicholas-de-Port locality in France. An archosaur tooth, possibly from a phytosaur, is also recorded. The new lepidosaur specimens add significant detail to the recently described ‘basal’ rhynchocephalian Penegephyrosaurus curtiscoppi as well as demonstrating that the global diversity of Lepidosauria in the Late Triassic remains incompletely known.

Trace fossils such as bite marks provide rare, direct evidence of animal behavior, including predator-prey interactions. We present an osteoderm of the aetosaur Typothorax coccinarum from the Late Triassic Chinle Formation of Arizona with several punctures and scores, interpreted here as bite marks, preserved as evidence of predation/scavenging by a large carnivore. The marks include a single bite producing four subparallel fusiform pits on the ventral surface and several additional marks, including striated scores, on the dorsal surface. These traces are described and compared with known contemporaneous carnivorous taxa to determine the source of the bite marks. Some Triassic carnivores, including theropod dinosaurs can be ruled out because of tooth shape and serration densities. Phytosaurs and large paracrocodylomorphs remain as likely candidates based on tooth morphology. Although some phytosaur teeth are too rounded to produce the marks seen in this specimen, we demonstrate that the more lingually flattened teeth typically found in the posterior section of the snout are sufficiently mediolaterally compressed to produce a fusiform pit. A protective function for aetosaur osteoderms cannot be confirmed presently, but the extensive carapace these bones formed would have been a major barrier to both scavengers and active predators and may preserve more feeding/predation traces than previously thought. The bite marks described herein support the hypothesis that aetosaurs were prey items of large archosauromorphs, expanding our understanding of the complex, and seemingly carnivore dominated Late Triassic terrestrial ecosystems of North America.

Regurgitalites (fossilized regurgitates) can provide insight into the behavioral ecology and physiology of extinct species but they are rarely reported because they are difficult to identify and distinguish from coprolites. A compact mass of skeletal material from the Owl Rock Member of the Upper Triassic Chinle Formation of Arizona reveals features that identify it as a regurgitalite. Characteristics of the teeth and osteoderms in the specimen indicate that these remains belong to the pseudosuchian archosaur Revueltosaurus. Chemical and microstructural analysis revealed a dearth of gastric etching, the preservation of muscle fibers, and the absence of a phosphatic matrix, indicating that this bone mass is a regurgitalite and not a coprolite. It was probably produced by a phytosaur, rauisuchid, or temnospondyl, all of which occur in the Owl Rock Member. We offer an identification key to assist in distinguishing between different types of digestive remains produced by vertebrate carnivores.

Heteropelta boboi is a new archosauriform reptile from the upper Anisian of northeastern Italy represented by a fragment of dorsal armor with a row of neural arches of the dorsal vertebrae. The dorsal armor of the new taxon is composed of two columns of paramedian osteoderms and at least six columns of lateral osteoderms. Unlike other armored archosaurs, the osteoderms are imbricated with the posterior osteoderm overlapping the anterior one. The low neural arches bear small neural spines and long postzygapophyses. The osteoderms of the lateral columns increase in size and change in shape from the most medial to the most lateral columns. Among the Archosauriformes, only the non-archosaur proterochampsians Vancleavea campi, Litorosuchus somnii, and the doswelliids have dorsal armor comprised of more than two columns of osteoderms per side, but the morphology and arrangement of their osteoderms is unlike those of the new Italian taxon. A cladistic analysis of Archosauromorpha positions Heteropelta boboi as either a basal phytosaur or a basal suchian. However, a second cladistic analysis focused on armored archosaurs alternatively positions the new taxon as a basal archosauriform, basal suchian, basal loricatan or crocodylomorph. Better resolution of the phylogenetic relationships of Heteropelta boboi will likely be obtained only with the discovery of cranial and postcranial remains associated with its diagnostic armor elements.

The Late Triassic vertebrate assemblages from Hallau, Switzerland, have been collected since 1915 and include sharks, bony fish (actinopterygians and lungfish), amphibians and archosau- riformes (a phytosaur and the dinosaur Plateosaurus). Many of the microtetrapods, including the haramyid and morganucodontid mammaliamorphs, are well known but the lepidosaurian reptiles have not been figured or described in any detail. We address that gap here reporting four distinct taxa in the 20th century collections made by Bernhard Peyer and emil Schutz. We describe a new basal rhynchocephalian, Deltadectes elvetica gen. et. sp. nov., which is of Gephyrosaurus-type grade rather than a sphenodontian. All the lepidosaurs in the fauna have teeth showing little or no replacement including a suppressed pleurodont and/or pleuracrodont dentition or acrodonty. A Diphydontosaurus- like sphenodontian is present and we record Paleollanosaurus,previously only known from the type locality in Texas U. S. A., together with an acrodont rhynchocephalian of uncertain affinities. The Hal- lau basal rhynchocephalians add further insight into the Norian-Rhaetian lepidosaur faunas found in Europe and North America by providing important new information, particularly to our knowledge of non-sphenodontian rhynchocephalians.

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.

Author(s): Lessner, Emily J.; Parker, William G.; Marsh, Adam D.; Nesbitt, Sterling J.; Irmis, Randall B.; Mueller, Bill D. | Abstract: The Upper Triassic Dockum Group of Garza County, Texas (lower, middle, and upper Cooper Canyon Formation) captures the radiation of Triassic non-marine tetrapods by preserving a variety of Late Triassic taxa from the southwestern United States. Our understanding of the vertebrate assemblage from these strata largely comes from a single site, the Post Quarry (lower Cooper Canyon Formation), with previous research documenting a variety of temnospondyls, sphenodontians, non-archosauriform archosauromorphs, and archosauriforms including a phytosaur, three species of aetosaurs, a poposauroid, a rauisuchid, a crocodylomorph, and several dinosauromorphs. To more completely reconstruct the vertebrate assemblage of the Dockum Group of Garza County we use an apomorphy-based approach to identify morphologically similar disarticulated and fragmentary elements from a variety of localities that span the entire Cooper Canyon Formation (Norian-Rhaetian), allowing assignments from the large clade level to the species level. Many skeletal elements are incomplete yet diagnostic and are assigned to the least inclusive clade if discrete character states do not allow for an unambiguous species-level identification. We identify new specimens referable to numerous clades including Tanystropheidae, Allokotosauria + Prolacerta + Archosauriformes, Vancleavea + Litorosuchus, Phytosauria, Paracrocodylomorpha, Dinosauriformes, and Saurischia, in addition to additional species identifications of the aetosaur Scutarx deltatlyus, and the dinosauromorph Dromomeron gregorii. Our study of this material demonstrates the utility of an apomorphy-based approach in making testable and repeatable observations for identifying small, isolated fragmentary fossil tetrapod material to reconstruct a more accurate faunal hypothesis for a portion of the Late Triassic of Texas. Previous claims of the earliest dinosaurs from near the base of the Dockum Group do not pass the apomorphy-based identification test, and the question of whether the oldest known North American dinosaurs are present in the Chinle Formation or Dockum Group can be resolved by utilizing vertebrate biostratigraphic correlation. Our revision of these fossil assemblages supports the hypothesis that early diapsids, early archosauromorphs, and non-dinosaurian dinosauromorphs were more common, diverse, and widespread in low latitudes during this time than previously thought.

A rostrum fragment from the marginal marine upper Lunz Formation of Austria (early Late Triassic: late Carnian) was previously identified as a new species of phytosaurian archosauriform, ‘Francosuchus’ trauthi. ‘Francosuchus’ trauthi was subsequently synonymized with the non-phytosaurid phytosaur Paleorhinus, and this synonymy was used as evidence to correlate the ‘Paleorhinus biochron’ and the Otischalkian land-vertebrate faunachron to the marine timescale. Here, I provide a redescription of ‘Francosuchus’ trauthi and document anatomical features that differ substantially from all known species of non-phytosaurid phytosaur. There is no evidence to support synonymy of ‘Francosuchus’ trauthi with Paleorhinus, and no unambiguous features to support a phytosaurian identification. However, ‘Francosuchus’ trauthi possesses a unique combination of characters that distinguish it from all other Triassic tetrapods, and necessitates referral of the species to a new genus, Dolerosaurus, gen. nov. Rejection ...

Phytosaurs are a clade of large, carnivorous pseudosuchian archosaurs from the Late Triassic with a near cosmopolitan distribution. Their superficial resemblance to longirostrine (long-snouted) crocodylians, such as gharials, has often been used in the past to infer ecological and behavioural convergence between the two groups. Although more than thirty species of phytosaur are currently recognised, little is known about the endocranial anatomy of this clade. Here, we describe the endocranial anatomy (including the brain, inner ear, neurovascular structures and sinus systems) of the two non-mystriosuchine phytosaursParasuchus angustifrons(=“Paleorhinus angustifrons”) andEbrachosuchus neukamifrom the Late Triassic of Germany based on digital reconstructions. Results show that the endocasts of both taxa are very similar to each other in their rostrocaudally elongate morphology, with long olfactory tracts, weakly demarcated cerebral regions and dorsoventrally short endosseous labyrinths. In addition, several sinuses, including large antorbital sinuses and prominent dural venous sinuses, were reconstructed. Comparisons with the endocranial anatomy of derived phytosaurs indicate that Phytosauria is united by the presence of elongate olfactory tracts and longitudinally arranged brain architecture—characters which are also shared with Crocodyliformes. However, a substantial morphological variability is observed in the cephalic and pontine flexure and the presence of a pineal organ across the different phytosaur species. These results suggest that the endocranial anatomy in Phytosauria generally follows a plesiomorphic pattern, with moderate variation within the clade likely resulting from divergent sensory and behavioural adaptations.

Phytosaurs are a diverse and morphologically distinctive clade of superficially crocodile-like archosauriforms that had a near global distribution during the Late Triassic. Because their remains are among the most abundant vertebrate remains recovered in many Upper Triassic terrestrial formations, phytosaurs are used extensively in long-range biochronological and biostratigraphic correlations. The biochronologically oldest and earliest branching known phytosaurs include an array of nominal species from the early Late Triassic of the United States, Germany, Poland, Morocco, and India that have been synonymized within the genus Paleorhinus, and subsequently used to define a global ‘Paleorhinus biochron’. However, recent phylogenetic work suggested that the North American species previously referred to Paleorhinus are paraphyletic. Here, we reassess the systematics and anatomy of putative specimens of Paleorhinus from southern Germany. Two well-preserved basal phytosaur skulls from the Blasensandstein (Carnian) of Bavaria form the holotypes of Francosuchus angustifrons and Ebrachosuchus neukami, both of which were synonymized with Paleorhinus by previous workers. We demonstrate that Francosuchus angustifrons shares unique synapomorphies with specimens referred to Paleorhinus bransoni from the Late Triassic of Texas, and thus refer the species to Paleorhinus. By contrast, the longirostrine Ebrachosuchus is highly distinctive in morphology, and our new cladistic analysis of Phytosauria demonstrates that it represents a valid taxon that is more closely related to Phytosauridae than to Paleorhinus. We provide the first autapomorphy-based support for a monophyletic but restricted Paleorhinus (supported by a nodal row on the jugal, and low paired ridges on the squamosal) and confirm that previous broader conceptions of Paleorhinus are likely to be paraphyletic. © 2013 The Linnean Society of London

The vomeronasal (VN) system is a pheromone-processing sensory system of tetrapods. Tetrapods use pheromones to communicate territorial boundaries, reproductive status, sex, and species identity. Presumed impressions of VN bulbs on phytosaur frontals led to a claim that phytosaurs possessed the VN system. However, in extant crocodilians, which lack the VN system, the corresponding impressions are associated not with cerebral tissue but with the ophthalmic nerves. Phytosaur head morphology was not conducive to pheromone collection. The extant phylogenetic bracket suggests that all extinct archosaurs, including phytosaurs, lacked the VN system. Without the pheromonal sense, they would not have used chemical means to convey territorial boundaries, reproductive status, sex, and species identity. Instead, they would have used visual, acoustic, and tactile cues, as in extant archosaurs and other tetrapods in which the VN sense is reduced or absent.

The Upper Triassic Tiki Formation of India is a rich storehouse of varied vertebrate fossil assemblages. So far, there is no information on taphonomic signatures of the Tiki vertebrate assemblages in comparison to that of other fossiliferous horizons of India. We report a new, low diversity, mono-dominant, multitaxic vertebrate accumulation where rhynchosaurs constitute the dominant component. The formation of the rhynchosaur bonebed is attributed to biological aggregation with a hydraulic overprint resulting in a mixed-origin concentration. Other taxa include rauisuchid, phytosaur, small indeterminate archosaur and cynodonts. Taphonomic study based on 617 skeletal specimens of rhynchosaurs collected from nine sites within an area of about 250 × 217 m 2 shows that most of the specimens are disarticulated and disassociated but in close spatial proximity to one another; some are associated specimens and few are articulated. About 13 to 20 individuals of rhynchosaur at different ontogenetic stages are estimated from the specimens collected, suggesting gregarious behavior, possibly herding. These specimens show varying degree of weathering, breakage, encrustation, abrasion and deformation. The bonebed is preserved within the Tiki red mudstone unit and is found in association with paleosol profiles, suggesting prolonged subaerial exposure. Spatial distribution and relative bone frequencies show differential susceptibility of the skeletal specimens to fluvial transport. 55.4% of the collected skeletal specimens belonged to Voorhies Group I, whereas 12.4% and 24% constituted Voorhies Groups II and III respectively, and 8.2% of the collected specimens belonged to the intermediate Groups I and II. It appears that the animals concentrated in the vicinity of the water sources during prolonged period of aridity and died possibly during high seasonal rainfall that resulted in a major flood event. Subsequently, the soft tissues decomposed, and the skeletons suffered prolonged subaerial exposure when the water receded leading to disarticulation and fragmentation followed by minor dispersion by low velocity water currents. This resulted in segregation of skeletal specimens, which were gradually covered by mud deposited during later flooding events. Based on the known flora and fauna, the Tiki Upper Triassic ecosystem is reconstructed for the first time. In the aquatic ecosystem, the metoposaurid labyrinthodonts occupied the top of the food pyramid together with the semi-aquatic parasuchids, which occupied an ecological niche similar to that of the present day crocodilians. The abundance of herbivorous rhynchosaurs at the base with few large and carnivorous rauisuchids and parasuchids at the top suggest a trophic structure similar to that of a modern day terrestrial ecosystem.

The recent discovery of Triassic tetrapod fossils in the Picket Wire Canyonlands of southeastern Colorado necessitates large-scale modification of the currently accepted stratigraphy of the area. The bone-bearing strata lie stratigraphically above a thick (∼80 meter [m]) eolianite historically identified as the Middle Jurassic Entrada Sandstone. The identifiable fossils include teeth and bone fragments of Late Triassic tetrapods, including metoposaurs, phytosaurs, and aetosaurs, recovered from thin (m-scale) discontinuous channels of limestone-pebble conglomerate deposited in a high-energy fluvial environment. Metoposaur bones consist of characteristically textured dermal bone fragments of the skull and pectoral elements, as well as a tooth. Phytosaur fossils consist of type C and B teeth, skull and jaw fragments, and some osteoderms. Aetosaurs are represented by several distinctive osteoderms, including some with evidence of prominent eminences and anterior bars. All identifiable tetrapods pertain to taxa known only from strata of Late Triassic age elsewhere, but none constrains the age of the fossil assemblage more precisely, although the assemblage is similar to lower Chinle Group assemblages of Carnian age (Otischalkian–Adamanian). The two most reasonable solutions to the discovery of Late Triassic index fossils stratigraphically above “Jurassic” beds are that the Triassic strata of this area have been mistakenly correlated with the Middle Jurassic Entrada Sandstone, or else the fossils are reworked into dramatically younger (Middle to Upper Jurassic) beds. The conglomerates are lithologically dissimilar from other Jurassic units regionally, but similar to Upper Triassic conglomerates of Wyoming (Gartra Formation) and New Mexico (Cobert Canyon Bed). Therefore, we consider the fossils to be in Upper Triassic strata. New lithostratigraphic data, including a composite measured section from the Picket Wire Canyonlands—as well as analysis and correlation of newly measured sections and others in the literature from south-central Wyoming, Colorado, Oklahoma, and New Mexico—suggest that the eolianite below the bone-bearing horizon and the finer clastic strata directly beneath the eolianite are best correlated to the Red Draw Member of the Jelm Formation. We correlate the bone-bearing conglomerates with the Cobert Canyon Bed at the base of the Chinle Group, described by previous authors as limestone and lithic-pebble conglomerate underlying the Travesser Formation in northern New Mexico. The gypsiferous and clastic strata overlying the conglomerates and below the Morrison Formation, ∼30 m higher in Picket Wire Canyon, are referred to the Middle Jurassic Ralston Creek (= Bell Ranch) Formation, a correlative of the Summerville Formation. These correlations extend the known distribution of Jelm Formation strata southeastward from north-central Colorado and south-central Wyoming and highlight the need for a major, modern restudy of this unit.

The Upper Triassic Canjilon Quarry in northern New Mexico preserves a vertebrate assemblage typical of the Norian Stage of North America. Although dominated in relative abundance by the phytosaur Pseudopalatus and the aetosaur Typothorax, a more diverse assemblage of smaller forms was previously reported. Additions to the Canjilon Quarry vertebrate assemblage are critically reviewed and described using an apomorphy-based method for assigning taxa. An apomorphy-based approach for compiling and comparing assemblages allows each taxonomic assignment to be a testable hypothesis. Fragmentary yet diagnostic elements that may not be assignable to a species-level taxon can be assigned to a larger clade and thus provide useful information. Additionally, each taxon listed in the assemblage must be tied to a diagnostic specimen listed with a museum specimen number. Using this method for the Canjilon Quarry, we establish the presence of an assemblage that is more similar to other vertebrate quarries near Gho...

We document here a new taxon of sphenodontian, Whitakersaurus bermani gen. et sp. nov., that is also the most complete sphenodontian fossil from the Upper Triassic Chinle Group in the south-western USA and the first Chinle sphenodontian represented by more than a single fragmentary dentulous element. The holotype was recovered during preparation of block C-8-82 from the famous Coelophysis (Whitaker) quarry at Ghost Ranch, New Mexico, and is the most complete small vertebrate recovered from the quarry. Detailed lithostratigraphy and geologic mapping demonstrate that the Whitaker quarry is in the Rock Point Formation of the Chinle Group, so Whitakersaurus is the first sphenodontian reported from this unit. Records of the phytosaur Redondasaurus at the quarry and elsewhere in the Chinle Group demonstrate that the quarry, and thus Whitakersaurus, is of Apachean (late Norian–Rhaetian) age. The sphenodontian specimen consists of incomplete left and right dentaries, a partial left? maxilla?, and impressions of a probable palatal element, all of which preserve multiple teeth. Whitakersaurus is distinct from other sphenodontians in possessing a unique combination of the following features: marginal dentition pleurodont anteriorly and posteriorly acrodont; pronounced heterodonty in dentary, with as many as 15 smaller, peg-like teeth anteriorly and several larger, posterior teeth that are conical and striated; faint radial ornamentation of posterior tooth crowns; presence of c. 19 dentary teeth; and absence of a distinct flange on posterior teeth. Numerous other details distinguish it from both more primitive and more derived taxa. Whitakersaurus, therefore, helps to document further mosaic evolution and an extensive diversification event of sphenodontians during Triassic time. Although sphenodontian taxa are relatively easily recognized, widely distributed, and common small- or microvertebrate fossils, the long stratigraphic ranges of taxa known from multiple specimens hinders their utility as index fossils with which to correlate strata across Pangaea.

The sequence of neurocentral suture closure is one criterion for the determination of ontogenetic stage in extant crocodylians. This pattern is frequently used to assess ontogeny for a variety of fossil archosaurs that may or may not follow the same sequence and timing of suture closure. Phytosaurs are one of the few basal archosaur groups with a sample size large enough to help test whether the crocodylian pattern of suture closure is plesiomorphic for Pseudosuchia and Archosauria. Analysis of a large sample of North American phytosaur specimens confirms that phytosaurs share the crocodylian state of closure, and so this pattern is probably plesiomorphic for the Pseudosuchia. An additional independent ontogenetic trend observed in phytosaurs is that the lateral fossae on cervical vertebrae in phytosaurs deepen with ontogeny. A preliminary survey indicates that there is considerable variation of both the sequence and timing of neurocentral suture closure in other archosaur clades. Therefore, it i...

Age assignments of Triassic tetrapod fossils can be achieved by direct reference to a scheme of Triassic land-vertebrate faunachrons (LVFs) that correlates Triassic tetrapod fossil assemblages to each other based solely on the tetrapod fossils. Correlation of Triassic tetrapod assemblages to the standard global chronostratigraphic scale (SGCS, the “marine timescale”) is a separate cross correlation between the vertebrate biochronology and marine biochronology that usually relies on other data (e. g., palynostratigraphy, magnetostratigraphy, radioisoto- pic ages) to be completed. Late Triassic tetrapod fossils in southern Poland are found at two stratigraphic positions, the Krasiejow and Lisowice levels. The tetrapod assemblage of the Krasiejow level is assigned to the early Adamanian LVF based primarily on the stratigraphic overlap of the phytosaur Parasuchus with the Adamanian index aetosaur Stagonolepis . The amphibians Cyclotosaurus and Gerrothorax , a Proterochersis -like turtle and the aetosaur Paratypothorax from the Lisowice level indicate it is assignable to the Revueltian LVF. Cross correla- tions to the SGCS are less definitive, but suggest that the Krasiejow level is late Carnian and the Lisowice level is early/middle Norian. However, this correlation of the Krasiejow level is confounded by disagreements over correlation of the marine Carnian–Norian boundary to nonmarine strata. Indeed, the possibility that the Krasiejow tetrapods fill a gap in the early Norian record of tetrapods merits consideration. Such difficulties emphasize the value of correlating tetrapod assemblages to each other using a land-vertebrate biostratigraphy/biochronology, instead of immediately attempting the more problematic correlation to the SGCS.

An incomplete well-preserved skull of a small phytosaur from the Upper Triassic New Oxford Formation of York County, Pennsylvania, resembles skulls previously referred to Rutiodon carolinensis in the plesiomorphic possession of a slender, uncrested rostrum. It differs from the latter only in the course of the palatal suture between the premaxilla and maxilla and the sharply notched anterior margin of the supratemporal fenestra. The type species of Rutiodon Emmons, 1856, R. carolinensis from the Cumnock Formation of North Carolina, cannot be adequately diagnosed at present and is considered a metataxon sensu Gauthier (1986). A very large tooth of a phytosaur from the same locality as the skull is not conspecific with the latter and indicates the existence of a second, much larger phytosaur in the New Oxford Formation.

An accumulation of skeletons of the pre-dinosaur Silesaurus opolensis, gen. et sp. nov. is described from the Keuper (Late Triassic) claystone of Krasiejow in southern Poland. The strata are correlated with the late Carnian Lehrberg Beds and contain a diverse assemblage of tetrapods, including the phytosaur Paleorhinus, which in other regions of the world co-occurs with the oldest dinosaurs. A narrow pelvis with long pubes and the extensive development of laminae in the cervical vertebrae place S. opolensis close to the origin of the clade Dinosauria above Pseudolagosuchus, which agrees with its geological age. Among the advanced characters is the beak on the dentaries, and the relatively low tooth count. The teeth have low crowns and wear facets, which are suggestive of herbivory. The elongate, but weak, front limbs are probably a derived feature.

The skull anatomy of a new species of the phytosaurMachaeroprosopusis described for the first time on the basis of two specimens from the Upper Triassic Cooper Canyon Formation of Texas. Additional information is provided by a third specimen referred toMachaeroprosopussp. A paranasal bone, an additional paired element of the narial region, is identified. Important new data are presented for the braincase, including the morphology of the epipterygoid and presphenoid, an anterior process of the prootic, an anteroventral process of the laterosphenoid, and a parasphenoid process.Machaeroprosopus lottorumn. sp. is characterised by four apomorphies: a supratemporal fenestra closed on the skull roof with bevelled anterior rim, a comparatively short squamosal, a flat and rugose narial rim, and medially extended palatines that come close to form an ossified secondary palate. With respect to the supratemporal fenestra, the supraoccipital–parietal complex and several features of the squamosal,Machaeroprosopus lottorumn. sp. bridges the morphological gap between species previously referred to the generaPseudopalatusandRedondasaurus. A parsimony analysis of known species ofMachaeroprosopussupports the hypothesis that the development of the rostral crest inMachaeroprosopusis a sexually dimorphic feature, and questions the validity of the genusRedondasaurus. Consequently,Redondasaurusis here considered a junior synonym ofMachaeroprosopus.

This paper reports a new assemblage from the Late Triassic (mid–late Carnian) at Woźniki near Częstochowa (Poland). The Woźniki vertebrate assemblage is similar to that of Lisowice–Lipie Śląskie, a new locality bearing vertebrates from latest Triassic (latest Norian–early Rhaetian) strata of southern Poland, in the presence of dicynodonts, shark spines, plagiosaurs and a cyclotosaur, but conchostracans and bivalves are similar to those from the Krasiejów site (late Carnian). The most complete specimen from Woźniki belongs to a dicynodont, and consists of cranial and postcranial bones of a single individual. It demonstrates that large dicynodonts were part of the Late Triassic vertebrate assemblage in Central Europe. Numerous tetrapod tracks and traces are associated with skeletal fossils at Woźniki.

The Stubensandstein (Upper Triassic, Norian) is a complex system of fluvial deposits in southwest Germany and yields one of the most diverse records of fossil vertebrates from the European continental Triassic. Taphonomic data from 17 partial skeletons of the prosauropod dinosaur Sellosaurus gracilis are presented, with emphasis on a recently rediscovered field sketch of one particular specimen. The preservational states and burial postures of individuals forming a practically monospecific prosauropod assemblage indicates in-situ preservation of single specimens, most likely by miring in unconsolidated fluvial sands covered by floodplain deposits. Shed teeth of carnivores and the mode of preservation suggest that one of the prosauropod carcasses was scavenged. At least two different types of predators, several individuals of a large indeterminate primitive archosaur and a phytosaur, left traces of their activities during scavenging on the carcass. The prosauropod-carnivore tooth assemblage provides the first evidence that deep-snouted phytosaurs with heterodont dentitions were capable of manipulating and feeding on large terrestrial prey. Moreover, scavenger–prey assemblages in the Norian of central Europe support the hypothesis that large carnivorous basal archosaurs (as represented for example by rauisuchians) were replaced by theropod dinosaurs in the Late Triassic.

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...

An unusual tetrapod tooth was discovered in the Upper Triassic Chinle Formation of southeastern Utah. The tooth was originally hypothesized to pertain to Revueltosaurus, but further investigations have rejected that hypothesis. In this paper, we compare MNA V10668 to other known fossil tooth crowns from the Chinle Formation and assign the tooth to the least inclusive clade currently available, Archosauriformes, based on the presence of mesial and distal serrations, a distal keel, and a conical mesiodistal profile. Using data found in other publications and pictures of other teeth, we compare this specimen to other Triassic dental taxa. MNA V10668 shares some similarities with Crosbysaurus, Tecovasaurus, and several other named taxa, including a teardrop-shaped labiolingual profile, but possesses a unique combination of characteristics not found in other archosauromorph teeth. This increases the known diversity of archosauromorphs from the Chinle Formation and represents the first tooth of this morphotype to be found from Utah in the Late Triassic.

An unusual tetrapod tooth was discovered in the Late Triassic Chinle Formation of southeastern Utah. The tooth was originally thought to belong to Revueltosaurus but further investigations have rejected that hypothesis. In this paper we compare MNA V10668 to other known fossil teeth found in the Chinle Formation and identify the least inclusive clade it may belongs to. Using data found in other publications and pictures of other teeth, we compare this specimen to other Triassic dental taxa. MNA V10668 shares some similarities with Crosbysaurus, Tecovasaurus, and several other named taxa but possesses unique characteristics not found in other diapsid teeth. We conclude that it is most likely an archosauromorph and probably an archosauriform. This increases the known diversity of tetrapods from the Chinle Formation and represents the first tooth morphotype completely unique to Utah in the Late Triassic Period.

(2001). A new Paleorhinus fauna in the Early Late Triassic of Poland. Journal of Vertebrate Paleontology: Vol. 21, No. 3, pp. 625-627.

SUMMARYStudy of casts ofStegomosuchus, a small reptile from the Upper Trias of the Connecticut Valley, hitherto regarded as a pseudosuchian thecodont, suggests that the skull ofProtosuchusincludes two pairs of supraorbital bones, and as a consequence the narrow interorbital region indicates a closer relationship to the South African genusNotochampsathan has previously been thought. These three genera of late Triassic crocodilians are placed in the family Stegomosuchidae von Huene, 1922.Proterochampsa,from the Ischigualasto Formation of Argentina, described by Reig (1959) and Sill (1967) as an ancestral crocodile, is considered to be an extremely primitive phytosaur.

Following the end-Permian extinction, terrestrial vertebrate diversity recovered by the Middle Triassic, and that diversity was now dominated by reptiles. However, those reptilian clades, including archosaurs and their closest relatives, are not commonly found until ~30 million years post-extinction in Late Triassic deposits despite time-calibrated phylogenetic analyses predicting an Early Triassic divergence for those clades. One of these groups from the Late Triassic, Phytosauria, is well known from a near-Pangean distribution, and this easily recognized clade bears an elongated rostrum with posteriorly retracted nares and numerous postcranial synapomorphies that are unique compared with all other contemporary reptiles. Here, we recognize the exquisitely preserved, nearly complete skeleton of Diandongosuchus fuyuanensis from the Middle Triassic of China as the oldest and basalmost phytosaur. The Middle Triassic age and lack of the characteristically-elongated rostrum fill a critical morphological and temporal gap in phytosaur evolution, indicating that the characteristic elongated rostrum of phytosaurs appeared subsequent to cranial and postcranial modifications associated with enhanced prey capture, predating that general trend of morphological evolution observed within Crocodyliformes. Additionally, Diandongosuchus supports that the clade was present across Pangea, suggesting early ecosystem exploration for Archosauriformes through nearshore environments and leading to ease of dispersal across the Tethys.

Phytosauria is a clade of large, carnivorous, semi-aquatic archosauromorphs which reached its peak diversity and an almost global distribution in the Late Triassic (c. 230–201 Mya). Previous phylogenetic analyses of Phytosauria have either focused primarily on the relationships of specific subclades, or were limited in taxonomic scope, and no taxonomically comprehensive dataset is currently available. We here present the most taxonomically comprehensive cladistic dataset of phytosaurs to date, based on extensive first-hand study, identification of novel characters and synthesis of previous matrices. This results in an almost twofold increase in phylogenetic information scored per taxon over previous analyses. Alongside a traditional discrete character matrix, three variant matrices were analysed in which selected characters were coded using continuous and landmarking methods, to more rigorously explore phytosaur relationships. Based on these four data matrices, four tree topologies were recovered. Relationships among non-leptosuchomorph phytosaurs are largely consistent between these four topologies, whereas those of more derived taxa are more variable. Rutiodon carolinensis consistently forms a sister relationship with Angistorhinus. In three topologies Nicrosaurus nests deeply within a group of traditionally non-Mystriosuchini taxa, leading us to redefine Mystriosuchini by excluding Nicrosaurus as an internal specifier. Two distinct patterns of relationships within Mystriosuchini are present in the four topologies, distinguished largely by the variable position of Mystriosuchus. In two topologies Mystriosuchus forms the most basal clade in Mystriosuchini, whilst in the others it occupies a highly derived position within the Machaeroprosopus clade. ‘Redondasaurus’ is consistently recovered as monophyletic; however, it also nests within the Machaeroprosopus clade. The greatest impact on tree topology was associated with the incorporation of continuous data into our matrices, with landmark characters exerting a relatively modest influence. All topologies correlated significantly with stratigraphic range estimates. Topological variability in our results highlights clades in which further investigation may better elucidate phytosaur relationships.