Uberabatitan ribeiroi, a new titanosaur from the Marilia Formation (Bauru Group, Upper Cretaceous), Minas Gerais, Brazil

摘要

A new Late Cretaceous titanosaur sauropod from the Bauru Basin of Brazil, Uberabatitan ribeiroi gen. et sp. nov., represented by at least three specimens, is described. The material comes from a level of coarse sandstone within the Serra da Galga sequence in Uberaba County, Minas Gerais State. The fossiliferous strata belong to the Marilia Formation (Serra da Galga Member), Bauru Group, considered to be Maastrichtian in age. The fossils occur in the uppermost levels of the above-mentioned unit; thus, Uberabatitan ribeiroi is the youngest titanosaur to have been recorded from the Bauru Basin. The autapomorphies that support the new species are: (1) anterior and mid-cervicals with postzygodiapophyseal lamina (podl) segmented in zygapophyseal and diapophyseal laminae, of which the first extends rostrodorsally over the second; (2) mid-dorsals with a robust lateral lamina formed mainly by a diapophyseal lamina (probably homologous to the postzygodiapophyseal lamina), and, to a lesser extent, by a relic of the spinodiapophyseal lamina (spdl); (3) mid (and probably posterior) dorsals with accessory neural laminae, which are lateral to the prespinal lamina, and probably homologous to the spinoprezygapophyseal laminae (sprl); (4) mid-caudal centra with deeply excavated lateral faces; (5) pubis very thick and robust, with a very stout longitudinal crest on its external (ventral) face; and (6) proximal end of the tibia with a prominent lateral protuberance, which articulates with an equally prominent medial knob of the fibula. The titanosaurian assemblage at Uberaba includes, apart from U. ribeiroi, well-preserved specimens assigned to species of uncertain affinities (Trigonosaurus pricei and Baurutitan britoi), as well as a few vertebrae assigned to aeolosaurines.