Notes on Didelphidae (Mammalia, Marsupialia) from the Huayquerian (Pliocene) of Argentina. American Museum novitates ; no. 2559

Abstract

"Late Tertiary beds in and around the Santa María valley of the Province of Catamarca, Argentina, were long known by the invalid name 'Araucanense' or derivatives therefrom. Thay can now be designated as a sequence of formations, from top to bottom: Corral Quemado, Andalgalá, Chiquimil A, and Chiquimil B. The Corral Quemado and Andalgalá formations are of Huayquerian (Pliocene, perhaps middle Pliocene) age. The age or ages of the Chiquimil are not adequately established. Didelphidae known from the Huayquerian of the Corral Quemado and Andalgalá are identified and a number of specimens described: Didelphis pattersoni, Lutreolina cf. crassicaudata, and ?Sparassocynus species innominata. Those three very different genera represent the reappearance in the known record of varied South American didelphids after a long gap from the Riochican (nominal late Paleocene) during which only a few quite different microbiotheres are known. The inferences are not only that sampling of small fossil mammals is inadequate in South America but also that much, perhaps most, of didelphid evolution was occurring outside the regions of known fossil fields"--P. 3.