Sobre el primer registro fósil del género “lystrophis” Cope, 1885 (Serpentes-Colubridae-Xenodontinae)

Abstract

The genus Lystrophis is distributed in the south of Brazil, Paraguay, Bolivia, Argentina and Uruguay. In Argentina are four species L. dorbignyi, L. pulcher, L. histricus y L. semicinctus, well-known usually with the name "falsa coral" (except L. dorbignyi called "falsa yarará", only that posses a Bothrops-like lepidosis). The specimen was found in the locality of Centinela del Mar, Buenos Aires province, in a level conformed for a diamicto asigned to the Bonaerian age (Middle to Upper Pleistocene). The material consist in a single troncal vertebra, lacking only the left prezigapophiseal process. This vertebra is allocated to the genus Lystrophis for the following group of traits: troncal vertebra more longer than wide, neural spine low and craneocaudally elongated, robust prezigapophisyal process and quadrangular shaped with a blunt apex and laterally oriented, pre-postzigapophises with oval shape. This morphology is concordant with the species compared (L. dorbignyi, L. pulcher y L. semicinctus), not existing differences at specific level that they allow a more precise assignment. This material represent the first fossil record of this genus, indicating the presence of this group of snakes since the Middle Pleistocene in South America.