Emended diagnosis and phylogenetic relationships of the Upper Cretaceous fossil snake Najash rionegrina Apesteguía and Zaher, 2006

Abstract

ABSTRACT—The fossil snake Najash rionegrina, from the Cenomanian–Turonian (Upper Cretaceous) of Argentina, is reinterpreted after examination of the type and referred material. The current diagnosis is emended in the light of important considerations that cast doubt on the attribution of type and referred specimens (a braincase, a quadrate, and two dentary/lower jaw fragments) used to systematize this taxon. Alternative interpretations of the anatomy of the sacrum and hind limbs are proposed. Following the reevaluation of the anatomy of the type specimen and the removal from this taxon of the above-mentioned referred material, the phylogenetic position of N. rionegrina was tested in a series of maximum parsimony analyses that included all groups of extant snakes, all best-known fossil snakes (i.e., Pachyrhachis, Haasiophis, Eupodophis, Madtsoiidae, and Dinilysia), and alternative outgroups. Regardless of the outgroup used to polarize the character-state transformations, our phylogenetic analyses found no support for the hypothesis that Najash rionegrina occupies a position as the most basal snake. Depending on the outgroup, Najash is placed (1) in a position basal to all living snakes, but more derived than other fossil forms (most notably Pachyrhachis, Eupodophis, and Haasiophis); or (2) as the most basal representative of a clade of fossil snakes that is the sister group of living snakes; or (3) as the most basal representative of a clade of fossil snakes that is located between the Scolecophidia and the Alethinophidia.

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

ACKNOWLEDGMENTS

We wish to thank most particularly, for their open hospitality and collegiality while we studied Najash, R. Barbieri and C. Muñoz (MPCA) in Cipoletti, Argentina. For assistance while working in various museum collections on comparative material, we wish to thank G. Teruzzi and C. Dal Sasso (MSNM); J.-C. Rage of the Muséum National d’Histoire Naturelle in Paris; D. Kizirian, R. Pascocello, and M. G. Arnold (AMNH); W. Boehme, P. Wagner, U. Bott, and C. Koch (ZFMK); and J. B. Losos, J. Rosado, J. Martinez, and T. Takahashi (MCZ). We are thankful for the useful comments and suggestions provided by the editor, P. O’Connor, and the two reviewers, J.-C. Rage and J. McCartney. This research was funded by the following grants: Alberta Innovates Ph.D. Student Scholarship to A.P.; an NSERC Discovery Grant (no. 238458–01) and Chair's Research Allowance to M.W.C.; and CONICET (PIP 112-200901-00176) to A.M.A.

Handling editor: Patrick O’Connor