Project 956: A. Palci, M. W. Caldwell, A. M. Albino. 2013. Emended Diagnosis and Phylogenetic Relationships of the Upper Cretaceous Fossil Snake Najash rionegrina Apesteguía and Zaher, 2006. Journal of Vertebrate Paleontology. 33 (1):131-140.
Specimen: † Najash rionegrina (MPCA:400)
View: dorsal


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.

Read the article »

Article DOI:

Project DOI: 10.7934/P956,
This project contains
  • 1 Media
  • 5 Documents
  • 1 Taxon
  • 1 Specimen
Total size of project's media files: 2.01M

Download Project SDD File
Currently Viewing:
MorphoBank Project 956

    Authors' Institutions

    • University of Alberta

    • Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)


    member name taxa specimens media
    MorphoBank Curator
    Project Administrator
    Last logged in 06/25/13
    Maureen Admin
    Full membership
    Last logged in 01/17/20
    Alessandro Palci
    Full membership
    Last logged in 05/20/13

    Project has no matrices defined.

    Project views

    type number of views Individual items viewed (where applicable)
    Total project views16252
    Project overview3795
    Specimen list2073
    Taxon list1748
    Documents list1689
    Media views4875Media search (4272 views); M287240 (603 views);
    Views for media list1170

    Project downloads

    type number of downloads Individual items downloaded (where applicable)
    Total downloads from project233
    Document downloads8Palci Matrix 1 (7 downloads); Character List (1 download);
    Project downloads224
    Media downloads1M287240 (1 download);