Cranial osteology of Bajadasaurus pronuspinax (Sauropoda, Dicraeosauridae)

ABSTRACT

The cranial remains of the holotype of the Lower Cretaceous Bajada Colorada Formation (Neuquén, Argentina) Bajadasaurus pronuspinax and its associated 3D model are studied and compared herein. These materials comprise a complete braincase, skull roof and occiput, several periorbital elements, several palatal elements, a partially complete upper jaw and complete lower jaw, a partially complete functional dentition, and an indeterminate element. Three potential synapomorphies for the taxon, related to the temporomandibular articulation area, were recognised, two of them in the quadrate and one in the squamosal. Four potential synapomorphies for Dicraeosauridae were recognised, related to the braincase and the jaws, in the orbitosphenoids, prefrontals, maxillae and dentaries, and surangulars. The new information highlights the variability and similarities among Dicraeosauridae, allowing the reassessment of previously suggested skull configurations within the group, which are reinterpreted here a presenting stylised lower jaws, and suggests the presence of a cornified sheath on the rostral portions of the muzzle, such as the observed in other dinosaurian groups.

KEYWORDS:

• Bajadasaurus pronuspinax
• cranial osteology
• dicraeosauridae
• sauropoda
• lower cretaceous
• cornified sheath

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2023.2212389.

Acknowledgments

We thank Juan Ignacio Canale (MMCh) for allowing the study of the holotype specimen of Bajadasaurus. JIC, Rogelio Zapata (MMCh), and Graciela Bianchi, Gustavo Cuevas, Eliana Guareschi and Angeles Antiao (Moguillansky Clinic) for providing assistance in the CT imaging collection. Phil Mannion (UCL) for assistance with Lingwulong. We thank Verónica Díez Díaz (MB.R.) and an anonymous reviewer, and the editor Gareth Dyke for their valuable comments towards an enhancement of the study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

JPG, PAG, JAW and NT contributed equally to this investigation in the Conceptualization, Methodology, Formal Analysis, Resources and Writing, except for the 3D digital modelling, performed by JPG.

Data archiving statement

Due to the fact that at the time of the publication these files on which the study is based represent the basis of the PhD studies of JPG, the CT scan files are available upon reasonable request to the authors.

Additional information

Funding

This work was supported by National Geographic Society under Grant ⧣W465-16; and Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación under grants PICT 2013-0704 and PICT 2018-00947.