Descrição anatômica e posicionamento filogenético de um dinossauro herrerassaurídeo proveniente do afloramento Cerro da Alemoa, Triássico superior de Santa Maria

• Ano de defesa: 2024
• Autor(a) principal: Boeira, Gabriel Alano
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Ciências Biológicas; UFSM; Programa de Pós-Graduação em Biodiversidade Animal; Centro de Ciências Naturais e Exatas
• Palavras-chave em Português: Dinosauria; Sistemática filogenética; Zoologia; Triássico; Phylogenetic systematics; Zoology; Triassic; CNPQ::CIENCIAS BIOLOGICAS
• Link de acesso: http://repositorio.ufsm.br/handle/1/33556

The specimen UFSM11608 was collected from the Cerro da Alemoa outcrop, within the Hyperodapedon Assemblage Zone (Carnian), in Santa Maria, Rio Grande do Sul, Brazil, and is housed in the collection of the Laboratório de Estratigrafia e Paleobiologia at the Federal University of Santa Maria. UFSM11608 is relatively complete, including the skull, forelimbs, and hindlimbs, but lacks the pelvic girdle, sacral vertebrae, and post-sacral vertebrae. The specimen shares several diagnostic traits of the Herrerasauridae clade, such as a robust, quadrangular premaxilla with a triangular posterolateral process that extends between the maxilla and the nasal. The mandible exhibits a sliding intra-mandibular joint, a short retroarticular process dorsally pronounced, and a dentary comprising 48% of the total mandible length, accompanied by a long mandibular fenestra representing 27% of the mandible’s length. In the axial series, the neural spines are robust and short, displaying grooves in their anterior and posterior regions, forming an “H” shaped cross-section. The scapula, on the other hand, has a long and slender blade with no distal expansion. When comparing UFSM11608 to other known herrerasaurids, it retains the ancestral condition of three premaxillary teeth, differing from Herrerasaurus ischigualastensis, which has four, and lacks the promaxillary fenestra observed in that taxon. Compared to Gnathovorax cabreirai, UFSM11608 is distinguished by the absence of an accessory lamina in the anterorbital fossa and less ventrally projected humeral epicondyles. In relation to Sanjuansaurus gordilloi, the specimen does not exhibit the diagnostic cervical protuberances present from the sixth to the eighth vertebrae. When compared to Staurikosaurus pricei, the absence of key elements such as the pelvic girdle and sacral vertebrae limits more detailed analyses. Nevertheless, UFSM11608 displays unique characteristics, particularly in the axial series, with robust vertebrae and short, elongated neural spines. These anatomical features suggest that UFSM11608 may occupy a distinct phylogenetic position within Herrerasauridae. While it is possible that it represents a new specimen of S. pricei, the unique morphology of its neck raises the possibility that UFSM11608 represents a previously unknown form within the group. Further analyses are required to confirm its position within the clade and its relationship to other herrerasaurids.