Roedores chinchilloideos (Hystricognathi) de la Formación Pinturas, Mioceno temprano – medio de la provincia de Santa Cruz, Argentina

KRAMARZ, A.

REVISTA DEL MUSEO ARGENTINO DE CIENCIAS NATURALES

Museo Argentino de Ciencias Naturales "Bernradino Rivadavia"

Lugar: Buenos Aires; Año: 2002 vol. 4 p. 167 - 180

1514-5158

The chinchilloid rodents are represented in the Pinturas Formation (Ameghino´s Atrapothericulan beds) by at least three species of the genus Perimys (P. intermedius sp. nov., P. erutus and Perimys sp.) and by one species of Prolagostomus. Perimys intermedius is only known from this unit. It can be distinguished form other species by having cheek teeth with narrower laminae with straight margins, wider hypoflexus and hypoflexid, lingual flexid only in m3, enamel reduced on the labial wall of the M3, completely absent on the labial wall of M1 and M2, and on the lingual wall of the m1 and m2. Variable size of the dentition is a result of ontogeny, as in other euhypsodont species. Based on this criterion and on morphological characters of the dentition, P. erutus Ameghino 1887 is considered as synonym of the following santacrucian species: P. diminutus, P. reflexus, P. angulatus, P. procerus and P. scalaris. The specimens of Prolagostomus from the Pinturas Formation show a dentition with an intermediate evolutionary condition between the Colhuehuapian and Deseadan chinchillids and the Santacrucian species of the genus Prolagostomus.