More than one? the hidden diversity of the limbed snakes of La Buitrera (Candeleros Formation, early Late Cretaceous) Argentina

FERNANDO FABIO GARBEROGLIO; MICHAEL WAYNE CALDWELL; SEBASTIAN APESTEGUIA; RANDAL NYDAM

Salt Lake City, Utah

Congreso; Society of Vertebrate Paleontology 76th annual meeting; 2016

Society of Vertebrate Paleontology

Najash rionegrina, the only limbed snake described from La Buitrera, northernPatagonia, Argentina, provides rare insights on the anatomy of Cretaceous snakeevolution in southern continents. It also addresses a number of important characters and character states that have traditionally been considered key synapopmorhies in supporting various phylogenetic schemes for snakes and their kin. N. rionegrina was diagnosed from an articulated postcranial skeleton with rear limbs, and associated cranial fragments. Subsequent fieldwork has produced six new skulls (7 total), some associated with postcrania, from a series of localities widely separated (up to 30 km), and along a stratigraphic interval through the last 70 m of the Candeleros Formation. The skulls and postcrania share a common general morphology; skull lengths range from small (~2cm) to large (~6-8 cm) and may well represent an ontogenetic series within the same species.Alternatively, the range of skull sizes, when linked to variation in postcranial anatomy (e.g., overally vertebral morphology, presence or absence of hypapophyseal keels/haemal keels, height of neural spines, etc.), also suggests that skull and postcranial variation might be explained by the presence of multiple species in the ?La Buitrera Paleontological Area Assemblage? (LBPA). In short, the ?LBPA Assemblage? is not necessarily an assemblage from a single population preserving juveniles and adults of a single species, but may be suggestive of a cluster of closely related species. These species, forming the ?Najash-assemblage?, share numerous features of the skull and skeleton in common with the younger ?Dinilysia-assemblage? (Río Colorado Formation, Argentina). These data support the presence of a Gondwanan lineage of closely related snakes.