A new Abelisauridae (Dinosauria: Theropoda) from São José do Rio Preto Formation, Upper Cretaceous of Brazil and comments on the Bauru Group fauna

ABSTRACT

Abelisaurid theropods are well-know from the Cretaceous of several parts of the Southern Hemisphere, including South America, Madagascar, and Africa, but also in India and Europe. Abelisaurids are high-diverse among other theropods with several cervicocephalic specializations reaching medium/large sizes. In the present contribution, we describe a new abelisaurid (Thanos simonattoi, gen. et sp. nov.) from the São José do Rio Preto Formation, Bauru Group, Brazil (Upper Cretaceous). Thanos differs from other theropods by having a well-developed keel becoming wider and deeper posteriorly on the ventral surface; two lateral small foramina separated by a relative wide wall on each lateral surface of the centrum, and well-developed and deep prezygapophyseal spinodiapophyseal fossae. The closed sutures between the axis and odontoid suggest that Thanos had reached a subadult/adult stage before death. Thanos is phylogenetically related to Brachyrostra abelisaurid. The keel on the ventral axial centrum in abelisauroids is here interpreted as a homoplastic condition that became more pronounced towards the phylogeny. The presence of well-developed keel in Thanos suggests that this taxon could be more derived than other abelisaurids. Finally, even though abelisaurids could reach large sizes, Thanos shared the environment with a larger theropod that was probably close to Megaraptora.

KEYWORDS:

• Theropods
• Brachyrostra
• vertebra
• axis
• Thanos simonattoi

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Acknowledgments

We would like to thank Sandra Aparecida Simionato Tavares and Cledinei A. Francisco (Museu de Paleontologia ‘Prof. Antonio Celso de Arruda Campos’), Paul Sereno and Bob Masek (University of Chicago), Alejandro Kramarz (Museo Argentino de Ciencias Naturales ‘Bernadino Rivadavia’) for providing access to the paleontological collections. FVI also acknowledge Antonio Celso de Arruda Campos (in memorian), Cledinei A. Francisco, Sérgio Luis Simonatto and Edvaldo Fabiano dos Santos for the efforts during the field work. We thank Federico Agnolin (Museo Argentino de Ciências Naturales) and two anonymous reviewers for important comments on the manuscript. We also thank Deverson da Silva (Pepi) for providing the Figure 4. RD also thanks Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES – PNPD 1760064) for its financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior [PNPD 1760064].