The postcranial skeleton of Teyujagua paradoxa (Reptilia: Archosauromorpha) from the early Triassic of South America.

Teyujagua paradoxa is a remarkable early archosauromorph from the Lower Triassic Sanga do Cabral Formation, Brazil. The species was originally described from an almost complete skull and a few associated cervical vertebrae, and no further postcranial elements were known at that time. Additional fieldwork in the Sanga do Cabral Formation, however, was successful in recovering a fairly complete postcranial skeleton attributable to the holotype. Here, we describe this new postcranial material, which is composed of cervical, dorsal, sacral and caudal vertebrae, limbs, pectoral and pelvic girdles, ribs, and gastralia. The description of its postcranial skeleton makes T. paradoxa one of the best-known early-diverging archosauromorphs. The cladistic analysis performed after the scoring of postcranial data recovered T. paradoxa in the same position initially described, close to the node that defines the Archosauriformes. Teyujagua paradoxa shares morphological features with representatives of early-diverging archosauromorphs and archosauriforms, with certain traits demonstrating a mosaic of plesiomorphic and apomorphic character states. We also performed partitioned morphospace and disparity analysis to elucidate the morphological disparity and evolutionary patterns among archosauromorphs. Teyujagua paradoxa occupies a notable position, suggesting an intermediate morphology between early archosauromorphs and proterosuchids. Disparity estimates highlighted Pseudosuchia and Avemetatarsalia as having the highest median disparity, reflecting their diverse cranial and postcranial morphologies, respectively. These findings offer valuable insights into archosauromorph macroevolution and adaptation.

Correction: A new archosauromorph from South America provides insights on the early diversification of tanystropheids.

[This corrects the article DOI: 10.1371/journal.pone.0230890.].

A new archosauromorph from South America provides insights on the early diversification of tanystropheids.

After the Permo-Triassic mass extinction, the archosauromorph fossil record is comparatively abundant and ecologically diverse. Among early archosauromorphs, tanystropheids gained considerable attention due to the presence of extreme skeletal adaptations in response to sometimes overspecialized lifestyles. The origin and early radiation of Tanystropheidae, however, remains elusive. Here, a new Early Triassic archosauromorph is described and phylogenetically recovered as the sister-taxon of Tanystropheidae. The new specimen, considered a new genus and species, comprises a complete posterior limb articulated with pelvic elements. It was recovered from the Sanga do Cabral Formation (Sanga do Cabral Supersequence, Lower Triassic of the Paraná Basin, Southern Brazil), which has already yielded a typical Early Triassic vertebrate assemblage of temnospondyls, procolophonoids, and scarce archosauromorph remains. This new taxon provides insights on the early diversification of tanystropheids and represents further evidence for a premature wide geographical distribution of this clade. The morphology of the new specimen is consistent with a terrestrial lifestyle, suggesting that this condition was plesiomorphic for Tanystropheidae.