Astrapotherium from the middle Miocene Collón Cura Formation and the decline of astrapotheres in Southern South America

KRAMARZ, A.; GARRIDO, A.; BOND, M.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2019 vol. 59 p. 290 - 306

0002-7014

Astrapotherium is the best-known member of theplacental order Astrapotheria. This large herbivorous inhabited the Patagonian ecosystems during earlyand middle Miocene times. The genus is widely represented in the early MioceneSanta Cruz Formation, with a dozen nominal species, of which A. magnum and A. burmeisteri  are the onlyones herein considered as valid. The middle Miocene record was limited to fewfragmentary remains from the Rio Frias Formation and presumably from the CollónCura Formation, described as A.hesperinum Cabrera 1940, a species name here interpreted as nomen vanum. Here we describe an almostcomplete skull with associated mandible derived from the Collón Cura Formationin the vicinities of Comallo, in Rio Negro Province (Argentina). It is largelythe most complete astrapothere material from middle Miocene rocks of highlatitudes, and it is referred to Astrapotherium guillei sp. nov. It differs from the remaining species essentiallyin lacking P3, achieved convergently with the latest diverginguruguaytheriines. Theastrapotheriines diversified in high latitudes during the early Miocene, butthey retained a stereotyped morphotype and became progressively less diverse,unlike their Northern counterparts (the Uruguaytheriinae). Astrapotherium guillei is the latest known Patagonianastrapothere and represents the final expression of the Astrapotheriinae´s declinethus far.