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Traversodontidae, a clade of gomphodont cynodonts, thrived during the Middle and Late Triassic, displaying a wide geographical distribution. During fieldwork in 2009, a new specimen was discovered in Ladinian/early Carnian stratigraphic layers in southern Brazil. Here, we describe this specimen and propose a new taxon closely related to Traversodon stahleckeri (Traversodontinae) but displaying a unique combination of traits (e.g., presence of a poorly developed suborbital process, mesiodistal length of the paracanine fossa similar to the length of the canine, short diastema between the fourth incisor and the upper canine, and coronoid process not entirely covering the distalmost lower postcanine). Furthermore, the endocranial anatomy of the new taxon was examined. The reconstruction of the cranial endocast revealed paleoneurological features consistent with non-Gomphodontosuchinae traversodontids. These features include the presence of a pineal body (but the absence of an open parietal foramen). These recent findings contribute significantly to our understanding of the evolutionary history and cranial anatomy of Middle-Late Triassic traversodontids, shedding light on the diversity and adaptations of non-mammaliaform cynodonts., (© 2024 American Association for Anatomy.)

Agudotherium gassenae is a poorly known non-mammaliaform probainognathian cynodont from the Late Triassic of southern Brazil. It is known only by mandibular remains, and its affinities within Probainognathia are unclear. Furthermore, its phylogenetic affinities were never investigated through computational analyses. In this study, we described new lower jaw remains excavated from the type locality and performed the first phylogenetic investigation of this taxon. The new specimen provides further anatomical information. The rostral region of the lower jaw was poorly preserved in the type series, leading to the interpretation that A. gassenae had three lower incisors. The new specimen demonstrates the presence of four incisors. The phylogenetic analysis positioned A. gassenae as the sister group of Prozostrodontia. This hypothesis differs from that previously presented in the former description of the taxon, in which it was considered a non-mammaliaform prozostrodont by means of character-state comparisons., (© 2023 American Association for Anatomy.)

Irajatherium hernandezi is a poorly known non-mammaliaform cynodont from the Late Triassic of southern Brazil. A new specimen of this cynodont was found in recent fieldwork to the type-locality, Sesmaria do Pinhal (Candelária), providing new insights into the anatomy of this mammalian forerunner. This specimen comprises a partial skull preserving the left canine, two left and three right postcanines, and an isolated exoccipital; the left dentary with the canine and postcanines; a fragment of the right dentary; the proximal portion of the left partial humerus; the right scapula; and indeterminate fragments. Based on new material, it is here suggested that I. hernandezi presents: a rostrum broad and short, possibly long as the temporal region; three foramina on the lateral surface of the maxilla, that could correspond to the external openings of the rostral alveolar, infraorbital, and zygomaticofacial canals; a slender zygomatic arch and an absent postorbital bar; a posteriorly wide temporal fossa; a long secondary palate, slightly surpassing the level of the last postcanine tooth; the cerebral hemispheres of the cranial endocast divided by a median sulcus; the scapular blade long and straight, and the postscapular fossa absent in lateral aspect. Finally, I. hernandezi and other tritheledontids were included in a phylogenetic analysis of Eucynodontia. The analysis recovered unresolved relationships for ictidosaurs/tritheledontids, nested within a polytomy with Tritylodontidae and a clade composed by Pseudotherium argentinus, Botucaraitherium belarminoi, Brasilodon quadrangularis, and Mammaliaformes., (© 2021 American Association for Anatomy.)

The Triassic of South America is known for its wide fossil diversity, which includes several terrestrial tetrapods, such as (but not restricted to) non-mammaliaform cynodonts, dicynodonts, early archosauromorphs, procolophonoids, pseudosuchians, and dinosaurs. However, carnivore archosaurs are rare from Brazilian Norian outcrops, being represented by sparse records of dinosaurs, one phytosaur, and some indeterminate isolated teeth. The São Luiz fossil site is one of Brazil's most iconic Norian outcrops, and a great diversity of fossils has already been found there. Most of them, however, are remains of small-sized taxa (less than 40 cm). Here, we describe an isolated tooth of a comparatively large archosaur from this site. The morphology of the new specimen indicates affinities with archosaurs, with serrations restricted to its distal carina and composed of sub-quadrangular denticles with a density of two to three denticles per millimeter. Despite being isolated, this new record adds information on the São Luiz outcrop diversity, indicating the presence of a still undescribed medium/large-sized carnivore. • The morphology of the new specimen CAPPA/UFSM 0050 indicates affinities with archosaurs. • This new record adds information to the vertebrate diversity of the São Luiz outcrop, Late Triassic from Brazil. • This new record indicates the presence of a still undescribed medium/large-sized carnivore for this locality. [ABSTRACT FROM AUTHOR]

The axial skeleton is proportionally underrepresented in the fossil record of early dinosaurs, when compared to other skeletal parts (e.g., pelvic girdle and hindlimb). For instance, the axis is poorly known in early dinosaurs, which precludes a better understanding of this important anatomical structure. Therefore, the present contribution fills an important gap with a description of the axis of a new early dinosaur (CAPPA/UFSM 0179). The specimen was collected at the Buriol outcrop, a Triassic fossiliferous locality from southern Brazil (Candelária Sequence, Santa Maria Supersequence) biostratigraphically correlated to Carnian units, placing this specimen among the oldest dinosaurs worldwide. Notable features include the combination of a neural spine that bears an almost straight dorsal margin along its length and presence of an epipophysis. This axis arrangement is unique among Carnian dinosaurs, representing a new morphotype, though a similar morphology is observed in some early theropods. Indeed, a phylogenetic analysis nested the specimen within Theropoda. However, this outcome is probably biased by the large amount of missing data in CAPPA/UFSM 0179 and also due to the limited sampling of the axis in early dinosaurs, particularly among sauropodomorphs. As the specimen comes from the site that includes Buriolestes schultzi (an early sauropodomorph), it is quite plausible that CAPPA/UFSM 0179 might be referable to that taxon. If so, the specimen improves the anatomical knowledge of Buriolestes schultzi, given its axis is yet unknown. An alternative possibility to be considered is that the specimen would belong to a dinosaur not yet known in the Candelária Sequence, which would increase its dinosaur diversity for the outcrop, improving the Triassic dinosaurian record from Southern Brazil. [ABSTRACT FROM AUTHOR]

The Triassic deposits of South America are key to understand the early radiation of Dinosauromorpha. Though the fossil record of the group is relatively abundant in Carnian- and Norian-aged strata from Argentina and Brazil, Middle Triassic dinosauromorphs are scarce, at least in the Brazilian record. In this contribution, we describe a set of fossils collected from a site biostratigraphically correlated to the Dinodontosaurus Assemblage Zone, which is regarded as Ladinian in age. Within the sample, we identified a single partial ilium with anatomical features consistent with Silesauridae. As a result, we propose a new taxon, Gamatavus antiquus gen. et sp. nov. as the first silesaurid from the Brazilian Middle Triassic. Biostratigraphic comparisons suggest the Dinodontosaurus Assemblage Zone to be older than the Argentinean Massetognathus - Chanaresuchus AZ, rendering the new specimen also the oldest South American silesaurid. This contribution adds to recent works that suggest biostratigraphical similarity between the Brazilian Dinodontosaurus AZ and the African Lifua Member and Ntawere Formation, from where the oldest dinosauromorph records are registered. • A new silesaurid, Gamatavus antiquus , is described. • The new material represents the oldest occurrence of the group in South America. • This is the first silesaurid record for the Dinodontosaurus Assemblage Zone. • It increases the similarity of the faunal content of Middle Triassic units in Brazil, Tanzania and Zambia. [ABSTRACT FROM AUTHOR]

Traversodontidae is a less inclusive clade of cynognathian cynodonts that lived during the Triassic. Recently, a traversodontid from the southern Brazilian Triassic beds was described – Siriusgnathus niemeyerorum – based upon specimens found exclusively in its type-locality. No absolute age or index fossils have been reported for this locality, which prevents an accurate biostratigraphic correlation. In the present contribution, we describe the first specimens of S. niemeyerorum found outside its type-locality, comprising skull portions excavated from outcrops in southern Brazil assigned to the Caturrita Formation (upper portion of the Candelária Sequence), Upper Triassic (Norian), Riograndia Assemblage Zone. As a result, we provide an updated biostratigraphic framework and suggest a Norian age for the type-locality of S. niemeyerorum , which, accordingly, possibly comprises the youngest South American traversodontid, pending additional geochronological studies in order to properly evaluate this hypothesis. • New specimens of the traversodontid Siriusgnathus niemeyerorum are described. • They represent the first records of S. niemeyerorum outside its type-locality. • The studied sites are assigned to the Riograndia Assemblage Zone, Norian. • Siriusgnathus niemeyerorum may be the youngest known South American traversodontid so far. [ABSTRACT FROM AUTHOR]

The Paraná Basin was filled by a sedimentary package deposited in successive sedimentation episodes related to the tectonic events that hit the SW portion of the Gondwana. The Triassic portion of this package, known worldwide for its continental tetrapod fauna, occurs only in the southern portion of the basin and is represented by 2 s-order sequences: the Sanga do Cabral Supersequence (SCS - Early Triassic) and the Santa Maria Supersequence (SMS - Middle-Late Triassic). The SCS fauna, including temnospondyls, parareptiles (mainly Procolophon), archosauromorphs, putative synapsids, and a number of indeterminate specimens, is traditionally considered Early Triassic and corresponds to the " Procolophon abundant zone" of the Karoo Basin (the upper levels of the Lystrosaurus AZ), in the upper Katberg Formation, which is Induan to early Olenekian in age. The sedimentary environment of the SCS is thought to be a wide alluvial plain, in which small and shallow channels spread northwards into a vast semiarid environment. By its turn, the Middle-Upper Triassic Santa Maria Supersequence is divided into four third-order sequences, from base to top: Pinheiros-Chiniquá, Santa Cruz, Candelária and Mata. Each of these sequences begins with fluvial deposition (low sinuosity rivers) that is overlain by transgressive shallow lacustrine deposits. The first three of these sequences present a very rich record of fossil tetrapods, including four successive faunal associations: Dinodontosaurus Assemblage Zone (Ladinian, within the Pinheiros-Chiniquá Sequence), Santacruzodon AZ (Ladinian/Carnian, in the Santa Cruz Sequence), Hyperodapedon AZ (Carnian) and the Riograndia AZ (early Norian), the latter two respectively at the base and top of the Candelária Sequence. In general, the lower portion of the package (Pinheiros-Chiniquá and Santa Cruz Sequences) was deposited under more basic and dried environmental conditions and are dominated by synapsids, while the top of the section (Candelária Sequence) is characterized by more acid and humid conditions and by a shift in the faunal content, with diapsids as dominating forms and presenting an increase of diversity compared to the lower biozones. • In Brazil, Triassic tetrapods are known only in the extreme south of the country. • The south Brazilian Triassic package includes four biozones based on tetrapods. • The lower tetrapod biozone of the Triassic package is Early Triassic and corresponds to the " Procolophon abundant zone" of the Karoo Basin. • Lower portion of the Middle-Late Triassic was deposited under more basic and dried environmental conditions and is dominated by synapsids. • Upper portion of the Middle-Late Triassic is characterized by more acid and humid conditions and presents an increase of diapsids compared to the lower portion. [ABSTRACT FROM AUTHOR]