An exceptional new specimen (CAPPA/UFSM 0035) of Buriolestes schultzi was discovered during recent fieldwork at the type locality of the taxon, which is Carnian in age (Late Triassic). This early sauropodomorph is peculiar owing to its faunivorous feeding habits, unusual amongst the members of this large omnivorous/herbivorous clade. The specimen incorporates new data on skeletal portions that have so far been unknown for B. schultzi, particularly regarding the skull and axial skeleton. As such, B. schultzi is now as complete as the best-known early dinosaurs, such as Eoraptor lunensis and Herrerasaurus ischigualastensis. A phylogenetic investigation fully supports B. schultzi as a sauropodomorph, corroborating the previous assignation. Despite the presence of traits found in Theropoda, distinct skeletal portions of B. schultzi do not share its morphospace in a morphological disparity analysis. We also propose an alternative evolutionary scenario for the first members of Sauropodomorpha: some Carnian taxa from South America form a monophyletic group instead of a series of low-diversity lineages paraphyletic with respect to Plateosauria.

Predatory dinosaurs were an important ecological component of terrestrial Mesozoic ecosystems. Though theropod dinosaurs carried this role during the Jurassic and Cretaceous Periods (and probably the post-Carnian portion of the Triassic), it is difficult to depict the Carnian scenario, due to the scarcity of fossils. Until now, knowledge on the earliest predatory dinosaurs mostly relies on herrerasaurids recorded in Carnian strata of South America. Phylogenetic investigations recovered the clade in different positions within Dinosauria, whereas fewer studies challenged its monophyly. Although herrerasaurid fossils are much better recorded in present-day Argentina than in Brazil, Argentinean strata so far yielded no fairly complete skeleton representing a single individual. Here, we describe Gnathovorax cabreirai, a new herrerasaurid based on an exquisite specimen found as part of a multitaxic association form southern Brazil. The type specimen comprises a complete and well-preserved articulated skeleton, preserved in close association (side by side) with rhynchosaur and cynodont remains. Given its superb state of preservation and completeness, the new specimen sheds light into poorly understood aspects of the herrerasaurid anatomy, including endocranial soft tissues. The specimen also reinforces the monophyletic status of the group, and provides clues on the ecomorphology of the early carnivorous dinosaurs. Indeed, an ecomorphological analysis employing dental traits indicates that herrerasaurids occupy a particular area in the morphospace of faunivorous dinosaurs, which partially overlaps the area occupied by post-Carnian theropods. This indicates that herrerasaurid dinosaurs preceded the ecological role that later would be occupied by large to medium-sized theropods.

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Aetosaurs are armored pseudosuchian archosaurs widespread in Upper Triassic units. In South America, four taxa were previously recorded: Aetosauroides scagliai, Neoaetosauroides engaeus, Aetobarbakinoides brasiliensis, and Chilenosuchus forttae. Herein we describe a new Late Triassic juvenile aetosaur from the Santa Maria Formation of southern Brazil, Polesinesuchus aurelioi gen. et sp. nov., increasing the paleobiodiversity of this interesting group to five taxa in Western Gondwana. The holotype is composed of cranial (parietal and braincase) and postcranial elements (cervical, dorsal, sacral, caudal vertebrae, both scapulae, a humerus, ilium, pubis, ischium, tibia, a partial right pes, and anterior and mid-dorsal paramedian osteoderms). It belongs to a juvenile individual, as its neurocentral sutures are open in all vertebrae, and also due to its small size. However, future paleohistological investigation is necessary to fully corroborate this assumption. This new taxon is distinguished from all other aetosaurs by the presence of an unique combination of character states (not controlled by ontogeny) such as: cervical vertebrae with prezygapophyses widely extending laterally through most of the anterior edge of the diapophyses; absence of hyposphene articulations in both cervical and mid-dorsal vertebrae; presence of a ventral keel in cervical vertebrae; anterior and mid-dorsal vertebrae without a lateral fossa in their centra; expanded proximal end of scapula; anteroposteriorly expanded medial portion of scapular blade; a short humerus with a robust shaft; and a dorsoventral and very low iliac blade with a long anterior process which slightly exceeds the pubic peduncle. Regarding its phylogenetic relationships, the present analysis placed Polesinesuchus as the sister taxon of Aetobarbakinoides and both as sister taxa of the unnamed monophyletic clade Desmatosuchinae plus Typothoracisinae.

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