Postcranial osteology and phylogenetic relationships of the Early Cretaceous titanosaur Tapuiasaurus macedoi Zaher et al. 2011

• Autor(a) principal: Navarro, Bruno Albert
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/41/41133/tde-14082019-095014/
• topic: 4. Osteologia; Cretáceo inferior; Early Cretaceous; Filogenia; Osteology; Phylogeny; Tapuiasaurus macedoi; Tapuiasaurus macedoi; Titanosauria; Titanosauria

Herein is presented a comprehensive description of the postcranial skeleton and phylogenetic analysis of the Early Cretaceous titanosaurian Tapuiasaurus macedoi Zaher et al. 2011. Tapuiasaurus becomes a key-taxon due its completeness, shedding new lights on the first steps in the early titanosaur evolution. The new information gathered by this study reveals that the presacral vertebrae anatomy of Tapuiasaurus possesses the typical apomorphic lithostrotian morphology (e.g. single neural spines, absence of hyposphene-hypantrum complex and aliform processes), whereas the architecture of fore and hindlimbs retains plesiomorphic characters, such as the presence of manual phalanges, as well as a pes with greater phalangeal count (=10). Contrasting with previous studies, the phylogenetic analysis retrieved Tapuiasaurus as an early lithostrotian, sister-taxon of the group formed by Yongjinglong datangi, from the Early Cretaceous of China, plus a relictual unnamed taxon from the Late Cretaceous of Minas Gerais State, the same region that in which Tapuiasaurus comes. The new recognized clade that would represents one of the first lithostrotian irradiations around the world, providing additional data that will help elucidate dispersion patterns in the group. This study reveals that the stepwise acquisition of the typical titanosaurian characters possesses a mosaic pattern, in which the apomorphic anatomy presented by the advanced titanosaurians was acquired along the last part of the Late Cretaceous, probably in the post Turonian time-interval (89.8 My)