The skull of Carnotaurus sastrei Bonaparte 1985 revisited: insights from craniofacial bones, palate and lower jaw

ABSTRACT

Carnotaurus sastrei: is perhaps the most iconic representative of the Abelisauridae family. It is known by a fairly complete specimen, recovered from Upper Cretaceous beds of southern Argentina. Here we present a re-study of the skull of Carnotaurus including detailed osteological descriptions, CT scans analyses and comparisons with abelisaurid taxa. Novel information concerning bones that remained undescribed (i.e., palate) is also offered. The present study allowed the recognition of several features, including some new potential autapomorphies diagnostic of Carnotaurus, such as nasolacrimal conduct with an accessory canal, ventral excavation on the quadrate and lateral fossa of the pterygoid. We identify some additional features of Carnotaurus shared with other abelisauroids, including: dorsal row of nasal foramina, lateral fossa on the squamosal, lanceolate vomeropterygoid process of palatine, apneumatic ectopterygoid and narrow and pointed angular process of surangular. CT scans revealed pneumatic recesses in the lacrimal which are similar to those present in other theropods. Furthermore, a striking feature is the presence of a small pneumatic recess on each frontal horn. Carnotaurus provides one of the most complete skulls within Abelisauridae, which allows recognising several traits of potential phylogenetic value and raises new questions regarding variability of cranial pneumaticity among ceratosaurs.

KEYWORDS:

• Skull
• osteology
• pneumatization
• abelisauridae
• cretaceous
• patagonia

Acknowledgements

We thank to Marcelo Isasi for the preparation of the material. We are grateful to Jorge O. Calvo (MUC), Guillermo Campos (MCNA), Martín Ezcurra (MACN), Rodolfo Coria (MCF), Eduardo Ruigómez (MPEF), Carlos Muñoz (MPCA), Mike Getty (UMNH), Michael Brett-Surman (USNM), Carl Mehling and Mark Norell (AMNH) and the personnel of the Geological Survey of India for allow the access to specimens under their care. We also thank the personnel and technicians of the Instituto TBA Salguero whom made possible the CT-scanning of the holotype. Alejandro Otero generously revised the English style of the manuscript. We deeply appreciate useful suggestions by Federico Agnolín on an early draft of the manuscript. We also thank Federico Brissón Egli, Martin Ezcurra, Mattia Baiano, Agustín Martinelli, Mauro Aranciaga-Rolando, Matías Motta and Juan Garderes for discussions and comments on theropod systematics and anatomy. Adriel Gentil generously helped on CT-scan analysis. We thank Pablo Puerta for his comments about the first stages of the preparation of Carnotaurus, and Santiago Reuil for his useful comments regarding retrodeformation. Finally, we are deeply grateful with Elena Cuesta and Matthew Carrano whom made valuable comments that greatly improved the quality of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by CONICET (Consejo Nacional de Investigaciones Científicas y Técnica) and Municipalidad of Villa El Chocón (Neuquén province, Argentina)Consejo Nacional de Investigaciones Científicas y Técnicas;