Una nueva especie del género Hydromedusa Wagler (Pleurodira, Chelidae) del Paleógeno de Patagonia

Abstract

A new species of the side-necked turtle referred to the genus Hydromedusa Wagler is described on isolated shell fragments discovered from a horizon of Cañadon Hondo Formation (lower Eocene) outcropping in eastern-central Patagonia. The holotype consists in a nuchal bone with a cervical (= extravertebral) scute recessed from the anterior margin of the carapace an autopornorhic condition present in the extant species of Hydromedusa. Several characters present in this extinct species (such as the wide first vertebral scute extended on the postero-Iateral extremities of the first peripheral bone, the proportion an position of the twelf marginal scales, the femoral/anal scales radio) suggest a specific differentiation from the extant species. The assignation of isolated fragments of the peripheral bones from Salamanca Forrnation (lower Paleocene) to the genus Hydromedusa extends in 10 m.a. the record of this genus in South America.