New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil

Abstract

Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group.

A juvenile sauropodomorph tibia from the 'Botucaraí Hill', Late Triassic of Southern Brazil

“…Reported taxa include the herrerasaurid Staurikosaurus pricei proposed by Colbert (1970) and the sauropodomorphs Saturnalia tupiniquim and Pampadromaeus barberenai described by Langer et al (1999) and Cabreira et al (2011), respectively, in addition to other reported undetermined or fragmentary remains (Müller et al, 2014(Müller et al, , 2016Pretto et al, 2015). These dinosaurs are part of a faunal assemblage coeval to that of the Ischigualasto Formation of northwestern Argentina, mostly due to the occurrence of the hyperodapedontid rhynchosaurs that characterize the Hyperodapedon Assemblage Zone (Schultz et al, 2000;Langer, 2005a,b).…”

Basal sauropodomorphs from the Ischigualasto Formation

“…Basal sauropodomorphs are represented in two of the oldest dinosaur-bearing geologic units, namely the Ischigualasto Formation of Argentina (Ezcurra et al, 2008;Ezcurra, 2010;Martínez and Alcober, 2009;Martínez et al, 2011) and the Santa Maria Formation of Brazil (Langer et al, 1999;Cabreira et al, 2011). For many years dinosaurs were thought to comprise a relatively small proportion of the archosaurs in the Ischigualasto fauna, including only the ornithischian Pisanosaurus (Casamiquela, 1967) and the theropods Herrerasaurus (Reig, 1963;Sereno and Novas, 1992) and Eoraptor .…”

Descrição osteológica e posicionamento filogenético de um terópode (Dinosauria, Saurischia) do Cretáceo Inferior da Bacia Sanfranciscana, município de Coração de Jesus, Minas Gerais, Brasil

“…No Brasil, Langer et al, 1999 e Pampadromaeus barberenai Cabreira et al, 2011. Ainda na Bacia do Parána, na Formação Caturrita, há registro de um provável terópode, o Guaibasaurus candelariensis Bonaparte et al, 1999.…”