A new sebecid mesoeucrocodylian from the Paleocene of northwestern Argentina

ABSTRACT

A new crocodyliform, Sebecus ayrampu, sp. nov., is described based on the rostral region of the skull, mandibular rami, and a distal portion of the femur collected in Paleocene rocks of northwestern Argentina. The new taxon is diagnosed (among other characters) by the presence of a sharp sagittal torus on the palatal surface of the premaxilla and maxilla, the surface of the alveolar region of the premaxilla descending vertically with respect to the palatal surface of the maxilla and the rest of the premaxilla, deep premaxillary fossa for the hypertrophied mandibular tooth with a ridge along its anterior margin, a differential pattern of ornamentation of the rostrum external surface, and a V-shaped anterior margin of the choana (with the vertex pointing anteriorly). This specimen is recovered as a new member of Sebecidae in a phylogenetic analysis, increasing the taxonomic diversity of the group in the Paleogene of northwestern Argentina. A sensitivity parsimony analysis using equal and implied weights (with different K values) retrieves two distinct lineages within Sebecidae: the Ayllusuchus + Bretesuchus clade and the Sebecus clade (in which the new taxon is included). Sebecidae is also recovered as a sister group to Baurusuchidae, forming together the monophyletic Sebecosuchia within Notosuchia.

http://zoobank.org/urn:lsid:zoobank.org:pub:7D924572-D642-4D00-982A-E08D734085F1

ACKNOWLEDGMENTS

We thank E. Ruigómez (Museo Egidio Feruglio, Trelew), A. Scanferla (IBIGEO), P. Ortiz, and R. González (Colección de Paleontología de Vertebrados Lillo, Universidad Nacional de Tucumán) for allowing us to access material under their care. We also thank A. Aresti for the preparation of the specimen, J. Powell for his valuable contribution to the knowledge of northwestern Argentina fauna, and J. R. Flores for his comments and advice on the phylogenetic analysis of this article. The manuscript greatly benefitted from valuable comments from the reviewers F. Montefeltro and J. M. Leardi, and from editors M. Young and J. Harris.

Additional information

Funding

This paper was supported and funded by the Universidad Nacional de Tucumán (PIUNT 2018 G-626 to D.A.G.L.), and the Agencia de Promoción Científica y Tecnológica (PICT 2016-3682 to G.B. and D.A.G.L., and PICT 2018-00605 to D.P.).