A new dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Brazil provides insights on the evolution of sauropodomorph body plan

Abstract

A new sauropodomorph dinosaur from the Late Triassic Candelária Sequence (Santa Maria Formation), south Brazil, Bagualosaurus agudoensis gen. et sp. nov., helps to fill a morphological gap between the previously known Carnian members of the group and younger sauropodomorphs. In some aspects, the skull, lower jaw, and dental anatomy of the new taxon approaches that seen in Norian forms like Pantydraco caducus, Efraasia minor, and Plateosaurus engelhardti. On the contrary, the post-cranial skeleton is broadly reminiscent of coeval, early dinosaurs. Although not reaching the size of most Norian and younger sauropodomorphs, B. agudoensis is significantly larger than coeval forms. The new data thus suggest that modifications in skull anatomy, possibly related to more efficient herbivorous habits, appeared early in sauropodomorph evolution, along with a moderate increase in size, followed in post-Carnian times by further increase in size, accompanied by more radical changes in post-cranial anatomy.

A dinosaur ilium from the Late Triassic of Brazil with comments on key-character supporting Saturnaliinae

“…Because ontogenetic data of most triassic dinosauromorphs are scarce, and many taxa are restricted to a single incomplete specimen (e.g. Colbert 1970, Martínez and Alcober 2009, Ezcurra 2010, Pretto et al 2018, Marsola et al 2019 the limited sample precludes the establishment of a reliable pattern to be followed as a model, whether regarding either ontogeny or individual variation. Once such traits could be related to intraspecific variation, we suggest caution when considering the faintness or roughness (i.e.…”

“…Nonetheless, the cranial tip of the preacetabular ala is rounded as also observed in most Carnian saurischians, for instance: Buriolestes schultzi, Saturnalia tupiniquim, Pampadromaeus barberenai and Zerfass et al 2007). "Marchezan" site (1), where an indeterminate herrerasaurid was collected; "Predebon" site (2), where tridactyl footprints attributed to indeterminate dinosaurs and to the ichnogenus Grallator were found (da Silva et al 2008); "Buriol" site (3), where the holotypes and referred specimens of Buriolestes schultzi and Ixalerpeton polesinensis were collected (Cabreira et al 2016, Müller et al 2017b, Müller et al 2018a; "Piche site" (4), where CAPPA/UFSM 0200 was collected; "Janner" site (5), where the holotypes and referred specimens of Bagualosaurus agudoensis, Pampadromaeus barberenai and other dinosauriform remains were collected (Cabreira et al 2011, Müller et al 2014, 2017b, Pretto et al 2015, Pretto et al 2018; "Sacisaurus" site (6); whereas the holotype and referred specimens of Sacisaurus agudoensis and indeterminate sauropodomorphs were collected (Ferigolo and Langer 2007); "Wachholz" site (7), whereas the holotype and paratypes of the sauropodomorph Macrocollum itaquii were collected (Müller et al 2018c); "Linha São Luiz" site (8), whereas referred specimens of Guaibasaurus candelariensis were collected (Langer et al 2011) and large tridactyl "theropod-like" footprints attributed to the ichnogenus Eubrontes were found (da Silva et al 2012).…”

“…this morphology contrasts with the pointed and/or elongated preacetabular ala observed in many post-Carnian sauropodomorphs such as Efraasia minor, Lessemsaurus sauropoides, Melanorosaurus, Pantydraco caducus, and Plateosaurus. Although other saurischians like Bagualosaurus agudoensis and Guaibasaurus candelariensis (UFrGS PV 0725t), and silesaurids as Asilisaurus kongwe and Silesaurus opolensis, present a similar condition that may be result of a taphonomic artifact (Pretto et al 2018). however, the ilium of Lutungutali sitwensis and some of the specimens of Silesaurus opolensis both give clues of the true aspect of this structure in silesaurids, because they possess more complete ilia (Peecook et al 2013, Piechowski et al 2014.…”

“…Over the last few years, outcrops from the Candelária Sequence (sensu horn et al 2014), have provided several exceptional dinosauromorph specimens (e.g. Cabreira et al 2011, 2016, Müller et al 2018a, Pretto et al 2018 from the interest to further recognize and identify dinosaurian specimens from the localities of this unit, because they hold fundamental data regarding the early evolution and radiation of dinosaurs. So far, the dinosaurian fauna from the Hyperodapedon AZ of the Candelária Sequence is mostly represented by herrerasaurids (Colbert 1970) and early-diverging sauropodomorphs (Langer et al 1999, Cabreira et al 2011, 2016, Müller et al 2018a, Pretto et al 2018, in which pelvic girdle/hindlimb remains are frequently sampled (e.g.…”

Dinossauromorfos triássicos do sul do Brasil e padrões biogeográficos da irradiação dos dinossauros

“…Similarly, the earliest definitive dinosaur body fossils are from the early Late Triassic (late Carnian) of [17][18][51][52][53][54] (Figure 3). Although the dating of many Laurasian rock sequences of putatively similar age is controversial, those in Germany (e.g.…”