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Characterized by an elongated snout, proterochampsids are carnivorous non-archosaur archosauriforms. The clade is endemic to South America and its fossil record extends from the early Carnian to the late Carnian/early Norian. Nesting close to Archosauria, it is a key clade for understanding the origin and evolution of archosaurian traits. Unfortunately, hind limb elements are usually poorly preserved for the group. Therefore, the hind limb anatomy of proterochampsids still lacks detailed descriptions. In the present study, we partially fill this gap with the description of a new proterochampsid represented by a complete and well-preserved hind limb. Stenoscelida aurantiacus gen. et sp. nov. was excavated from the late Carnian/early Norian (Late Triassic) beds of southern Brazil. A phylogenetic investigation recovers the new taxon as a non-rhadinosuchine proterochampsid. The species bears an unusual set of traits for the group, which provides clues on the evolutionary origins of some muscle attachment structures. For instance, the femur of Stenoscelida aurantiacus gen. et sp. nov. possesses an anterior trochanter and an anterolateral scar. So far, these features have not been reported in other non-archosaurian archosauriforms. Therefore, the new specimen indicates that some typical archosaurian features evolved earlier than previously thought. The taxon also carries additional uncommon features for proterochampsids, such as an iliofibularis tubercle on the anterior margin of the fibula and a vestigial phalanx in digit V. In sum, Stenoscelida aurantiacus has one of the best-preserved hind limbs within Proterochampsidae and sheds light on the polarization of important traits regarding the evolutionary context of Archosauria. [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]

Proterochampsids are one of the several diapsid groups that originated, flourished and became extinct during the Triassic Period. The current fossil record of this group indicates that its species were restricted to continental assemblages of the early Late Triassic of South America. The recent description of new rhadinosuchine proterochampsid specimens from the Chañares Formation (early Carnian, Argentina) increased the morphological diversity of the group and cast doubts on their current taxonomic scheme. Previous authors have pointed out that available diagnoses do not allow specimens to be referred unambiguously to the different rhadinosuchine species. Here we redescribe, figure and compare in detail the holotype of one of these rhadinosuchine species, Chanaresuchus bonapartei from the Chañares Formation. The new information provided here allows us to discuss the degree of post-mortem deformation present in the specimen and check the character scorings for the proterochampsid species sampled in the most comprehensive phylogenetic data set currently available for Permo–Triassic archosauromorphs. Our new cladistic analyses find stronger support than previous studies for the monophyly of Rhadinosuchinae and the clades that include Doswelliidae + Proterochampsidae and Tropidosuchus + Rhadinosuchinae. Doswelliids are recovered within Proterochampsidae, as the sister taxon to the genus Proterochampsa, in some analyses under implied weights. Some characters present a phylogenetic signal consistent with the latter grouping, but one additional step is required to force it in the analysis under equal weights. We consider that the new anatomical and phylogenetic information provided here is a step towards a necessary taxonomic revision of Rhadinosuchinae and further research on the interrelationships of proterochampsian archosauriforms. [ABSTRACT FROM AUTHOR]

Rhynchosaurs are a clade of quadruped, herbivorous stem-archosaur diapsids restricted to the Triassic Period. The group became globally distributed and the numerically dominant tetrapods of several terrestrial ecosystems before their extinction. Derived rhynchosaurs are characterized by a specialized masticatory apparatus, composed of a blade-and-groove occlusion with multiple longitudinal maxillary tooth rows. The morphology of the maxillary tooth plate has shown to be taxonomically and phylogenetically informative. So far, two rhynchosaur maxillary tooth plate morphotypes are known in Argentina, one belonging to an unnamed stenaulorhynchine from the Chañares Formation and the other to the hyperodapedontine Hyperodapedon sanjuanensis, the single rhynchosaur species currently name for the Ischigualasto Formation. Here we describe a new rhynchosaur maxillary tooth plate morphotype based on an indeterminate hyperodapedontine specimen from the Ischigualasto Formation. This maxillary tooth plate (PVL 2728) possesses a single longitudinal groove that divides symmetric lateral and medial tooth-bearing areas with relatively large tooth crowns, which is an uncommon combination of features among hyperodapedontines. These qualitative observations in addition to quantitative analyses show that the morphology of PVL 2728 differs from that of, at least, other sampled South American rhynchosaurs. Therefore, this specimen expands the morphological disparity of rhynchosaurs in northwest Argentina and southwestern Pangaea. [ABSTRACT FROM AUTHOR]

Teraterpeton hrynewichorum is an unusual archosauromorph reptile from the Upper Triassic (Carnian) Evangeline Member of the Wolfville Formation in Nova Scotia (Canada). Its long snout has transversely broad, cusped 'molariform' teeth posteriorly and lacks teeth anteriorly. The temporal region of the cranium is 'euryapsid' with large upper and closed lower temporal fenestrae. A previously undescribed specimen referable to Teraterpeton includes a nearly complete pelvic girdle and both hind limbs. The ilium has a long, dorsoventrally deep anterior process similar to that of derived rhynchosaurs. The pelvis has a well-developed thyroid fenestra, a feature shared only by Tanystropheidae among Archosauromorpha. Metatarsal V is proximodistally short, resembling the condition in Tanystropheidae. The pedal unguals of Teraterpeton are strongly flattened mediolaterally, dorsoventrally deep and weakly curved, much like the manual unguals. We performed a phylogenetic analysis of a matrix comprising 61 taxa of Permo-Triassic diapsid reptiles and 337 characters, which supports the position of Teraterpeton as the sister-taxon of Trilophosaurus + Spinosuchus. In the current phylogeny, parsimony-based character optimization of the aforementioned character-states in Teraterpeton indicate that all were acquired independently from other saurian lineages. The unusual combination of postcranial features in Teraterpeton underscores the critical importance of comprehensive taxon sampling for understanding the mode of character change among Triassic diapsid reptiles and careful apomorphy-based identifications to faunal analyses. [ABSTRACT FROM AUTHOR]

Three small and gracile jaw fragments are recovered from the Boren Quarry, one of the lowest fossil quarries of the Upper Triassic Dockum Group of Texas. The specimens are referred to archosauromorphs, where the morphology of the dentary and teeth of two specimens resemble what is observed in basal saurischians. Growing numbers of early dinosaur fossils from the lowest quarries of the Dockum Group of Texas which correspond to the lowermost Norian raises doubts concerning early dinosaur dispersal during the late Carnian-early Norian interval and the first occurrence of North American dinosaurs which might have happened earlier than previously suggested. [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]

Proterosuchids are a clade of quadrupedal, carnivorous Permo-Triassic diapsids crucial to understand the successful evolutionary radiation of archosaurs during the Mesozoic. The importance and good fossil record of proterosuchids nourished a renewed interest in recent years, but no function has been proposed for their bizarre snouts. An oversized and downturned premaxilla with up to nine teeth with continuous replacement is present in all proterosuchid species and seems to have represented a physiologically costly phenotype that increased towards adulthood. A non-functional or a species recognition hypothesis are not supported as evolutionary mechanisms that drove this phenotype because features expected for these explanations tend to have a very low or zero physiological cost. There is no evidence favouring – but neither rejecting − that this morphology can be explained by non-sexual and non-social natural selection alone. Mutual social and/or sexual selection is favoured here as the most unambiguously supported explanation for the function and origin of the bizarre snout of proterosuchids based on several lines of evidence, including costliness, positive allometry, positive changes in growth rates and modern analogues. Social and/or sexual selection may have been important evolutionary mechanism in the dawn of the lineage that gave rise to crocodiles and dinosaurs. [ABSTRACT FROM PUBLISHER]

In this contribution, we report a distal portion of a left humerus that likely belongs to an indeterminate basal archosauromorph from the Guadalupian (mid-Permian) Rio do Rastro Formation (Paraná Basin) of southern Brazil. A precise taxonomy of the fragmented and isolated humerus UFRGS-PV-0546-P is not warranted at generic nor familiar level but, likely, this specimen belongs to an Archosauromorpha due to the lack of both the entepicondylar and the ectepicondylar foramina. The narrow distal end of the humerus, the rounded radial and ulnar condyles, and the moderately developed supinator process with a shallow ectepicondylar groove (not notched) are features reminiscent of tanystropheids rather than that of other archosauromorphs. This material likely represents the first and oldest Permian archosauromorph from South America and indicates the presence of this lineage before the P/T boundary. [ABSTRACT FROM AUTHOR]

European Russia has yielded several fragmentary but potentially important archosauriform specimens from the Middle Triassic, but these have been only briefly described in the literature. One of these puzzling taxa isDongusuchus efremoviSennikov, 1988, described from the Donguz Svita. We present a redescription ofDongusuchus efremovi, which includes the first photographic atlas and thorough anatomical description of the holotype and referred specimens. This taxon is shown to be a gracile, probably fast-running species with elongate and slender limbs. A phylogenetic analysis recoversDongusuchus efremovias an early-diverging, non-archosaurian archosauriform. Previous work had suggested that this taxon was a ‘rauisuchid’. The gracile proportions of the femur and somewhat wedge-shaped head, however, are unusual for basal archosauriforms and are similar to the plesiomorphic state in crocodile and avian-line crown archosaurs. Several Early-Middle Triassic basal archosauriforms and early members of the crocodile and avian lineages were gracile with elongate, slender limbs. This suggests that the limb morphology ofDongusuchus efremovimay be plesiomorphic for Archosauria and proximal clades. [ABSTRACT FROM AUTHOR]

Arambourg was the first to conduct methodical vertebrate palaeontological studies in the Oulad Abdoun and Ganntour phosphatic basins of Morocco between the 1930s and 1950s. As early as 1935, he identified the main stratigraphical levels of the phosphatic series, characterizing them by a specific association of vertebrates (mainly selachians), and proposed stratigraphical correlations between the phosphatic levels of these two basins. During the last decade, due to a French-Moroccan program of collaboration, vertebrate fossils have been collected in great abundance. Here we present an updated overview of the latest Cretaceous to Ypresian reptilian faunas from the Oulad Abdoun and Ganntour basins, on the basis of published data and new field records. In addition to advances in the study of the already known taxa (i.e., squamates, crocodyliforms, plesiosaurs), recent field works reveal new major reptilian taxa that were unknown (or undescribed) at Arambourg's time: very abundant and diversified marine chelonians (Maastrichtian to Ypresian), scarce dinosaurs and pterosaurs remains (Maastrichtian), and a well diversified marine avifauna (Thanetian and Ypresian). A significant increase in the number of described taxa (52 versus 13) and an improvement of the quality of the specimens found (articulated skeletons versus isolated remains) is worthy of consideration. The Maastrichtian reptilian assemblages are dominated by mosasaurid squamates whereas those of the Palaeogene are by the mirroring crocodyliforms (dyrosaurids and eusuchians). [ABSTRACT FROM AUTHOR]

Supplemental materials are available for this article for free atwww.tandfonline.com/UJVP Citation for this article: Jaquier, V. P., and T. M. Scheyer. 2017. Bone histology of the Middle Triassic long-necked reptilesTanystropheusandMacrocnemus(Archosauromorpha, Protorosauria). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1296456. [ABSTRACT FROM AUTHOR]