New records of aquatic snakes (Squamata, Palaeophiidae) from the Paleocene of South America

FERNANDO FABIO GARBEROGLIO; GÓMEZ, RAÚL ORENCIO; CALDWELL, MICHAEL WAYNE

General Roca

Congreso; Reunión de comunicaciones de la Asociación Paleontológica; 2023

Asociación Paleontologica Argentina

The Paleocene deposits from the Cerrejón Formation in La Guajira, Colombia, have provided abundant snake remains, mostly isolated vertebrae and ribs. All this material has been assigned to the giant snake Titanoboa cerrejonensis, the only taxon currently described from this locality. During the study of the referred materials to this snake, we found that some of them, part of the specimen UF/IGM 16, do not correspond to Titanoboa. This suggests the presence of a second large-bodied snake taxon from the La Guajira locality. This non-Titanoboa taxon is recognized from three articulated vertebrae, a second set of two articulated vertebrae, and one isolated vertebra. All six vertebrae display a distinct morphology that differs from Titanoboa. They are morphologically identical, of a consistent size (but are not necessarily from the same individual), and represent a new taxon of large dimensions that is estimated to be around eight meters in total length (based on vertebral measurements and total length measurements obtained from extant snakes). Anatomical comparisons show that these vertebrae possess features typical of the Palaeophiidae, such as massive and moderately laterally compressed vertebrae, poorly developed pterapophyses, slightly demarcated subcentral ridges, reduced prezygapophyses, and horizontally oriented condyle. The Palaeophiidae are a group of extinct snakes of uncertain relationships known mostly from vertebrae; they show varying degrees of adaptation to semi-aquatic, aquatic, and marine lifestyles. Among the Palaeophiidae, the new taxon from the Cerrejón Formation can be assigned to the Palaeophiinae. The new taxon resembles the more generalized forms assigned to the genus Palaeophis, but lacks the extreme aquatic adaptations that define the genus Pterosphenus. We regard the new taxon as an undetermined palaeophiine and do not assign it to Palaeophis as a number of features differ from that described genus, including strongly inclined prezygapophyses from the horizontal plane, weakly projected ventrally synapophyses, presence of parazygantral foramina, and only one short hypapophyses, posteriorly positioned. The oldest records assigned to Palaeophiidae are from the Cretaceous of Africa, and Paleocene records are poorly known and restricted to Africa, North America and Europe. However, the majority of the forms assigned to Palaeophiidae are from the Eocene, principally from the Tethys region with only one previous SouthAmerican record coming from the Eocene of Ecuador. This new record expands the known diversity of aquatic snakes from the Paleogene of South America and provides a substantial new record for the paleogeographical distribution of Palaeophiidae.