Boiruna cf. B. maculata (Ophidia: Colubroides) from the Early to Middle Pleistocene of Argentina, and the Effects of Pleistocene Extinctions on South American Reptiles

Abstract

A new specimen referable to Boiruna cf. B. maculata from a Lower-Mid Pleistocene locality in Ramallo, Buenos Aires, Argentina is described, representing the first fossil record of this genus. This specimen is referred to this living genus on the basis of the following features: robust supratemporal bone very wide at mid-length; subcentral process of the basioccipital with three well-developed subequal projections forming a wide, flat, posteriorly indented surface; lymphatic fossae of trunk vertebrae wide and deep, with well developed subcentral ridges; and third cloacal vertebra with anteroposteriorly extended neural spine, amongst others. This record is outside the current geographical range of the species of this genus, indicating warmer environmental conditions at the end of the Ensenadan age in Buenos Aires province. As in other continents, the South American fossil Pleistocene record indicates that Pleistocene extinctions affected mainly (and perhaps only) large reptiles.