Leonardo Kerber

Traversodontids were diverse non‐mammaliaform cynodonts that occupied herbivorous and omnivorous niches during the Middle and Late Triassic. In Brazil, they are particularly well represented in the Santa Maria Supersequence, although the taxonomic status of some historically described taxa remains uncertain. Among them, “ Traversodon (?) major” von Huene, 1936 was established on the basis of isolated cranial, mandibular, and postcranial remains from the Chiniquá region of southern Brazil. Here, we reassess the anatomy and taxonomic affinities of the specimens historically assigned to this species. A left maxilla (GPIT‐PV‐61005, here designated as lectotype) is the most informative specimen. It exhibits a combination of a broad maxillary platform, a maxillary recess, and strongly shouldered postcanine alveoli, supporting traversodontid affinities but not the original assignment to the genus Traversodon. These features are typical of deeply nested gomphodontosuchines, but do not form a unique combination of diagnostic characters that would allow a confident referral to any particular genus. The remaining specimens have no association or anatomical overlap with the lectotype and are here treated independently: the mandibular fragment is referred to Traversodontidae indet., the humerus to Eucynodontia indet., and the scapulocoracoid to an indeterminate non‐cynodont amniote. Accordingly, “ Traversodon (?) major” is retained as a nomen dubium : its lectotype lacks autapomorphies, and the remaining specimens cannot be reliably referred to the same taxon.

Traversodontids are non‐mammaliaform cynodonts, herbivorous to omnivorous, that lived during the Triassic. In the Late Triassic, some members of this group increased in body size relative to other cynodont lineages and evolved postcranial adaptations associated with locomotion. The Late Triassic Siriusgnathus niemeyerorum is one such traversodontid. Originally described in 2018 based on cranial material, the species has since been the focus of considerable advances in our understanding of its skull anatomy; however, its postcranial skeleton remains undescribed. The present study examined the postcranial osteology of this traversodontid, focusing on the pectoral girdle and forelimb of the specimen CAPPA/UFSM 0109, paratype of the species. These remains show that Si. niemeyerorum presents a scapulocoracoid with concave anterior and posterior margins and a lateroventrally oriented glenoid fossa formed by the scapula and coracoid; a humerus with a short diaphysis and a broadly open deltopectoral crest; an ulna with a developed olecranon process; and a manus with a phalangeal formula of 2‐3‐3‐3‐3. One of the distal carpals (dc1) is greatly elongated and morphologically similar to a metacarpal, a feature observed in some gomphodonts. The combination of traits present in the scapulocoracoid (glenoid) and the robustness of the humerus suggests a lateralized (“sprawling”) forelimb posture in Si. niemeyerorum , similar to that inferred for Exaeretodon argentinus and Exaeretodon riograndensis . In summary, this study expands current knowledge of traversodontid postcranial anatomy and provides new insights into the locomotor adaptations among non‐mammaliaform cynodonts.

Nowadays, Lepidosauria is a diverse group represented by squamates and the rhynchocephalian tuatara. However, their origins date back to the end of the Permian Period, when the stem lineages Lepidosauromorpha and Archosauromorpha diverged. Within the lepidosauromorph stem lineage, a few species have been described with unstable phylogenetic placements. In Brazilian strata, the only representative of this lineage is the rare species Cargninia enigmatica . The taxon was found in Norian beds (upper portion of the Candelária Sequence) and is known from the posterior end of a dentary and a tentatively referred partial maxilla. Here, we describe a new specimen (CAPPA/UFSM 0519) referred to Cargninia enigmatica , consisting of a partial dentary recovered from the type locality. The specimen provides new anatomical information on the anterior portion of the dentary. In addition, for the first time, the phylogenetic placement of Cargninia enigmatica was investigated in a computational framework, and the results are congruent with previous suggestions that it represents a non‐lepidosaur lepidosauromorph. Finally, the new specimen reveals details of the anatomy of the mandibular ramus of the trigeminal nerve, demonstrating that it shares a similar condition with its extant relatives.

Prozostrodon brasiliensis , a probainognathian cynodont of the clade Prozostrodontia, is recognized as a key taxon for understanding the origin of Mammaliaformes and mammals. Despite detailed investigations of its cranial anatomy, the postcranial skeleton has received comparatively less attention. In this contribution, we present a multi‐proxy approach to study new postcranial elements assigned to an individual of P. brasiliensis from the Marchezan outcrop ( Hyperodapedon Assemblage Zone of Santa Maria Supersequence, Upper Triassic, Rio Grande do Sul, Brazil), integrating anatomical, osteohistological, and phylogenetic data. The analyzed elements include parts of the pectoral girdle (left scapulocoracoid and left clavicle), forelimb (right and left humeri), hindlimb (left femur, tarsal, and metatarsal elements), and caudal vertebrae. The postcranial skeleton exhibits a mosaic of plesiomorphic and derived features, indicating an intermediate morphological (and possibly functional) condition within Prozostrodontia. The anatomy of the scapulocoracoid and humerus suggests a transitional forelimb posture, whereas the femur and hindfoot indicate a generalized, predominantly terrestrial locomotor pattern. Elongated amphicoelous caudal vertebrae further suggest a proportionally long and functional tail, likely contributing to balance and body stabilization. Osteohistological analyses of the humerus and femur show predominance of a woven‐parallel complex, consistent with relatively high growth rates. The presence of two growth lines indicates cyclical deposition, whereas the absence of an external fundamental system (EFS) and the lack of a marked decrease in vascularization suggest that the individual had not yet reached skeletal maturity at the time of death. A phylogenetic analysis was performed incorporating newly defined humeral characters and a revised set of postcranial characters modified from previous datasets. Phylogenetic mapping of postcranial characters reveals recurrent patterns of homoplasy within Probainognathia, highlighting the anatomical diversity of non‐mammaliaform cynodonts. Together, these results provide new insights into the postcranial record of Prozostrodon brasiliensis and reinforce its significance for understanding the postcranial evolution of the mammal forerunners.

Triassic pseudosuchians had highly diversified cranial morphologies. These archosaurs occupied diverse ecological roles, ranging from terrestrial predators and herbivores to semiaquatic ambush predators and possible waders. Here, we apply linear cranial morphometrics to assess possible convergences with other sauropsids from the clades Theropoda, Squamata, and Plesiosauria and discuss their paleoecology, based upon what was known for the aforementioned clades. Thus, a total of 34 specimens of Triassic pseudosuchians and theropod dinosaurs were added to a morphometrics dataset originally used to infer the ecology of the enigmatic theropod Spinosaurus aegyptiacus . Principal component analysis and permutational multivariate analyses of variance were used to evaluate morphospace occupation and group differentiation. Our results indicate that linear variables are capable of distinguishing semiaquatic and aquatic taxa from terrestrial taxa, but fail to distinguish between semiaquatic and fully aquatic taxa, and could not distinguish between the different niches of the sampled terrestrial taxa. Phytosaurs cluster close to marine squamates, Qianosuchus mixtus occupies an intermediate position between the phytosaurs and the crocodylomorphs, erpetosuchids plotted near varanids. Beaked pseudosuchians did not cluster close to beaked theropods, with Effigia okeeffeae overlapping with Baryonyx walkeri . The loricatans, and possible synonymous, Decuriasuchus quartacolonia and Prestosuchus chiniquensis overlapped. Some loricatans plot near ornithomimids, and Saurosuchus galilei cluster close to Acrocanthosaurus atokensis . We conclude that convergent morphologies do not necessarily reflect convergent function in Triassic pseudosuchians. The research of their paleoecology would benefit from the integration of morphology and function rather than morphology and convergence, especially with obscure taxa such as the poposauroids.

Recent work has suggested that the presence of extraoral soft tissues (‘lips’), in the form of labial scales in theropod dinosaurs, could be inferred based on: anteroposteriorly distributed foramina in the rostral bones, similar to extant lepidosaurs; vertically projected teeth; uniform enamel thickness in maxillary teeth; and an allometric relation between skull length and maxillary crown height. Here, we review the current state of knowledge on the presence of lips in saurischian dinosaurs and further contribute to the debate by inferring and discussing their presence in Triassic archosauromorphs, particularly those from southern Brazil, using the same methodological approach. Our results support the hypothesis that the lipped condition represents the plesiomorphic state in Sauropsida. Non‐theropod Triassic saurischians and pseudosuchians exhibit a foraminal distribution similar to that of theropods and extant lepidosaurs. Histological thin sections reveal a uniform enamel thickness on both labial and lingual sides of functional and shed tooth crowns, and the dentine shows no evidence of wear, contrasting with the condition in crocodilian teeth. Additionally, our regression analysis supports an allometric trend in which increased skull length correlates with increased maxillary crown height in Theropoda, Sauropodomorpha, Herrerasauria and Pseudosuchia. We also infer and discuss the presence of a mandibular gap in Prestosuchus , as well as the occurrence of lips in specialized taxa from the clades Theropoda, Ornithosuchidae, Phytosauria and Proterosuchidae, based on convergent rostral features shared with extant lepidosaurs and actinopterygians. Furthermore, we examine the presence of both rhamphotheca and labial scales across the clades Silesauridae, Lagerpetidae and Rhynchosauria.

There is a growing consensus that pterosaurs and the flightless Lagerpetidae are closely related. This relationship is supported by apomorphies throughout the skeleton, including endocranial character states such as a well‐developed floccular fossa and a tall anterior semicircular canal. Our knowledge of lagerpetid anatomy has been improved by recent discoveries. Among them, the Brazilian record plays a significant role, having produced two described species, Ixalerpeton polesinensis and Venetoraptor gassenae , and several more fragmentary specimens. In this study, we used an x‐ray micro‐computed tomographic scan to describe the endocranial anatomy of the holotype of Venetoraptor gassenae . The endocranial anatomy of Venetoraptor gassenae is similar in shape to that of other described lagerpetids, and we reach the following conclusions: (1) in pterosaurs, the metotic foramen exits posteriorly, whereas in lagerpetids and dinosauromorphs it exits through the lateral wall of the braincase; and (2) Venetoraptor gassenae is unique among lagerpetids in having only one exit for cranial nerve XII, expanding its differential diagnosis. These differences highlight that the braincase anatomy of lagerpetids is aligned with the anatomical disparity observed in the group. Finally, we discuss why future studies should focus on comprehending patterns of braincase pneumaticity in avemetatarsalians.