Gondwanatheria is an enigmatic mammaliaform clade distributed in the Cretaceous and Paleogene of South America, Africa, Madagascar, India and Antarctica. The Mesozoic record in South America is restricted to the Latest Cretaceous of Río Negro and Chubut provinces, Argentina and Magallanes Region of southern Chile. The aim of the present contribution is to describe a new specimen of gondwanatherian mammaliaforms from beds belonging to the Maastrichtian Chorrillo Formation, cropping out 30 km SW of El Calafate, Santa Cruz Province, Argentina. It is represented by a single molariform referable to the species Magallanodon baikashkenke with which it shares a unique combination of characters. Analysis of the unique combination of characters exhibited by Magallanodon shed doubts on the monophyly of Ferugliotheriidae and suggest that South American taxa may be closely related to each other. The wide geographical distribution and occurrence of gondwanatherians on geological units of diverse origins suggest that they were capable of facing disparate environmental conditions.

冈瓦纳特里亚（Gondwanatheria）是分布在南美，非洲，马达加斯加，印度和南极的白垩纪和古近纪的神秘哺乳动物类进化枝。南美的中生代记录仅限于里奥内格罗和丘布特省的最新白垩纪，阿根廷和智利南部的马加拉内斯地区。本文稿的目的是描述属于Maastrichtian Chorrillo组的河床中的冈瓦纳第哺乳动物形态的新标本，该标本裁剪出阿根廷圣克鲁斯省El Calafate西南30公里处。它由一个单一的象形代表，该种指的是Magallanodon baikashkenke种，与之共有独特的性状组合。Magallanodon展示的字符的独特组合分析引起了对Ferugliotheriidae科的怀疑，并暗示南美类群可能彼此密切相关。冈瓦纳特人的广泛地理分布和发生在不同起源的地质单位上表明他们有能力面对不同的环境条件。