UN NUEVO BORHYAENINAE (MARSUPIALIA) DEL PLIOCENO MEDIO DE HIDALGO (LA PAMPA)

Abstract

The present paper deals with a new Borhyaeninae (Marsupialia) which has been found in limolitic sediments in the Salinas Grandes of Hidalgo cliffs, La Pampa 1ttlvince, Argentina. In the first part details of the Formation Epecuen and Hidalgo sediments are given. The correlation of the best know mammal bearing formations of Pliocene tl 1 in Argentina are summarized in a table. In the second part, the new specimen is described and compared with other Borhyaeninae. In this group the di.fferentiation of the diverse morphologic sectorial types (related with a more or less carnivore diet) is common to all members, but it was attained following different ways. In the case of Borhyaenidium musteloides, the sectorial type of the lower molars is a result of the reduction of the talonid tl111' to the displacement of the entoconid towards the outside, and the reduction of the ldpoconulid. In the upper molars the sectorial type is attained by the anterior displacement the protocone, which is located almost in the same line uniting the metacone with the llltilllstilar projection.