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

New fossil material of Auliscomys formosus Reig 1978 allows restudy of the oldest known South American representative of the subfamily Sigmodontinae, Auliscomys formosus was based on a fragmentary dentary exhumed from the Monte Hermoso Formation of central Argentina. Previous studies allocated A. formosus to the early Pliocene. A revaluation of dental and cranial morphology, including for the first time the upper dentition, and the inclusion of A. formosus in a phylogenetic analysis of the tribe Phyllotini, indicates that A. formosus represents a new genus, Kraglievichimys. Kraglievichimys shares a mosaic of characters with the living Auliscomys Osgood, 1915 and Loxodontomys Osgood, 1947. The taxonomic reassignment of A. formosus and the possibility that the Monte Hermoso Formation may be younger than Early Pliocene in age provides 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 of K. formosus suggests that the South American history of sigmodontines spans less than 4 million years.

1978年Reig命名的优美囊鼠（Auliscomys formosus）的新材料化石，使得我们得以重新研究已知最古老的南美棉鼠亚科（Sigmodontinae）代表类群。此前该物种仅基于一件从阿根廷中部蒙特埃尔莫索组（Monte Hermoso Formation）发掘出的残破齿骨定名。以往研究将优美囊鼠的生存时代归为上新世早期。本次研究对其牙齿与颅骨形态（首次包含上齿列）进行重新评估，并将优美囊鼠纳入叶鼠族（Phyllotini）的系统发育分析中，结果显示该物种实际代表一个新属——克拉格莱维奇鼠属（Kraglievichimys）。克拉格莱维奇鼠属与现生的囊鼠属（Auliscomys Osgood, 1915）和洛索多鼠属（Loxodontomys Osgood, 1947）具有镶嵌式演化的特征组合。对优美囊鼠的分类学重新厘定，以及蒙特埃尔莫索组的地质时代可能比上新世早期更年轻的新认识，为南美仓鼠科（Cricetidae）的类群分化研究提供了全新视角。此前基于分子手段对棉鼠亚科起源年代的估算结果均偏向更古老的时间节点，而本次对克拉格莱维奇鼠（Kraglievichimys formosus）演化历史的新解读表明，棉鼠亚科在南美的演化历史跨度不足400万年。