A New Giant Titanosauria (Dinosauria: Sauropoda) from the Late Cretaceous Bauru Group, Brazil

Abstract

Titanosaurian dinosaurs include some of the largest land-living animals that ever existed, and most were discovered in Cretaceous deposits of Argentina. Here we describe the first Brazilian gigantic titanosaur, Austroposeidon magnificus gen. et sp. nov., from the Late Cretaceous Presidente Prudente Formation (Bauru Group, Paraná Basin), São Paulo State, southeast Brazil. The size of this animal is estimated around 25 meters. It consists of a partial vertebral column composed by the last two cervical and the first dorsal vertebrae, all fairly complete and incomplete portions of at least one sacral and seven dorsal elements. The new species displays four autapomorphies: robust and tall centropostzygapophyseal laminae (cpol) in the last cervical vertebrae; last cervical vertebra bearing the posterior centrodiapophyseal lamina (pcdl) bifurcated; first dorsal vertebra with the anterior and posterior centrodiapophyseal laminae (acdl/pcdl) curved ventrolaterally, and the diapophysis reaching the dorsal margin of the centrum; posterior dorsal vertebra bearing forked spinoprezygapophyseal laminae (sprl). The phylogenetic analysis presented here reveals that Austroposeidon magnificus is the sister group of the Lognkosauria. CT scans reveal some new osteological internal features in the cervical vertebrae such as the intercalation of dense growth rings with camellae, reported for the first time in sauropods. The new taxon further shows that giant titanosaurs were also present in Brazil during the Late Cretaceous and provides new information about the evolution and internal osteological structures in the vertebrae of the Titanosauria clade.

How has our knowledge of dinosaur diversity through geologic time changed through research history?

“…The general patterns of 'global' subsampled diversity shows a steady increase from Middle to the end of Jurassic with a decline through J/K transition Tennant, Mannion & Upchurch, 2016b). The relatively high Late Cretaceous subsampled diversity levels can at least be partially explained by the constant discovery of new titanosaurian taxa, especially from Gondwanan continents (Vieira et al, 2014;de Jesus Faria et al, 2015;Bandeira et al, 2016;Poropat et al, 2016), and only recently a more appreciated diversity of diplodocoids (e.g. dicraeosaurids, rebbachisaurids) from relatively poorly sampled regions such as Africa (Mannion & Barrett, 2013;Wilson & Allain, 2015;Ibrahim et al, 2016).…”

Peer Review #2 of "How has our knowledge of dinosaur diversity through geologic time changed through research history? (v0.1)"

“…The general patterns of 'global' subsampled diversity shows a steady increase from Middle to the end of Jurassic with a decline through J/K transition Tennant et al 2016b). The relatively high Late Cretaceous subsampled diversity levels can at least be partially explained by the constant discovery of new titanosaurian taxa, especially from Gondwanan continents (Vieira et al 2014;de Jesus Faria et al 2015;Bandeira et al 2016;Poropat et al 2016), and only recently a more appreciated diversity of diplodocoids (e.g., dicraeosaurids, rebbachisaurids) from relatively poorly sampled regions such as Africa (Mannion & Barrett 2013;Wilson & Allain 2015;Ibrahim et al 2016).…”

The last dinosaurs of Brazil: The Bauru Group and its implications for the end-Cretaceous mass extinction

“…There has been little work on the geochronology of the formation, but it is often considered to be Campanian-Maastrichtian in the literature (e.g., Azevedo et al 2013, Bandeira et al 2016. This is largely based on lithological correlations that indicate lateral gradational contacts between the Presidente Prudente Formation and the Adamantina Formation, whose age has been determined as latest Santonian-Maastrichtian through more intensive study (see above) (Zaher et al 2006, Simbras 2009).…”

“…Many of these belong to Aeolosaurini, a subgroup of derived titanosaurian sauropods currently known only from the Late Cretaceous of South America. Aeolosaurins from the Adamantina Formation include Gondwanatitan, described from a set of bones that includes parts of the neck, back, sacrum, tail, pectoral and pelvic girdles, and fore and hind limbs (Kellner and Azevedo 1999); Maxakalisaurus, represented by an incomplete disarticulated holotype skeleton (Kellner et al 2006) and a partial right dentary and isolated teeth (França et al 2016) (although see Bandeira et al 2016 for an alternative phylogenetic placement) (Fig. 4a); and Aeolosaurus maximus, based on an articulated skeleton that preserves portions of the neck, tail, and fore and hind limbs (Santucci and Arruda-Campos 2011).…”

“…One recent analysis found Baurutitan to be a fairly derived titanosaur in a polytomy with the lineages that led to Saltasauridae and Aeolosaurini, meaning that it is plausible that it could belong to either of those characteristic South American clades (França et al 2016). However, another recent study by Bandeira et al (2016) recovered Baurutitan in a much more basal position, far removed from the aeolosaurins and as sister taxon to the mid Cretaceous Drusilasaura from Argentina. This latter analysis also found Uberabatitan within Saltasauridae (as the sister taxon to Brasilotitan), but Trigonosaurus in a more primitive position, in a small clade with Tapuiasaurus from the Early Cretaceous of Brazil and the putative aeolosaurin Maxakalisaurus (see above).…”