The oldest sigmodontine rodent revisited and the age of the first South American cricetids

Abstract

AbstractNew fossil material ofAuliscomys formosusReig 1978 allows restudy of the oldest known South American representative of the subfamily Sigmodontinae. Description ofAuliscomys formosuswas based on a fragmentary dentary exhumed from the Monte Hermoso Formation of central Argentina. Previous studies allocatedA. formosusto the early Pliocene. A reevaluation of dental and cranial morphology, including for the first time the upper dentition, and the inclusion ofA. formosusin a phylogenetic analysis of the tribe Phyllotini indicate thatA. formosusrepresents a new genus,Kraglievichimys.Kraglievichimysshares a mosaic of characters with the livingAuliscomysOsgood, 1915 andLoxodontomysOsgood, 1947. The taxonomic reassignment ofA. formosusand the possibility that the Monte Hermoso Formation may be younger than early Pliocene in age provide a new understanding of cricetid diversification in South America. Estimates of sigmodontine ancestry by molecular approaches are biased toward older ages, whereas this new interpretation of the history ofK. formosussuggests that the South American history of sigmodontines spans less than 4 million years.UUID:http://zoobank.org/49dd8f60-56b1-4e8a-a044-6cea3a1bd52b