Xenungulates are a peculiar group of bilophodont ungulates, widespread over South America during the Paleocene and early Eocene. Here we describe, illustrate and analyse a new Xenungulata, Rodcania kakan gen. et sp. nov., the first from the lower latitudes of Argentina. It was recovered from the Río Loro Formation (Tucumán Province), for which a Paleocene age was estimated. The material comprises a fragment of the left dentary with an incomplete m2, eroded over the enamel surface, and an almost complete m3. Both teeth share with Xenungulata strong enamel, vertically oriented Hunter–Schreger bands (HSB), and wear facets sloping distally. Rodcania kakan differs from other xenungulates in the m3 trigonid, simplified and mesiodistally short; absence of a paraconid; more oblique protolophid in relation to the mesiodistal axis and a straight cristid obliqua, pointing to the protoconid position; and has a wider and longer talonid. A phylogenetic analysis of 13 species and 36 craniodental characters recovered R. kakan as a basal member of the Carodniidae, supported by 10 synapomorphies in the four most parsimonious trees. The body mass estimation of the Río Loro Fauna and of the rest of the xenungulate taxa revealed that R. kakan is the largest mammal of the Río Loro assemblage, weighing around 165 kg and with a size comparable to Carodnia feruglioi. The increase in body mass showed no clear relation with evolutionary trends in xenungulates.

http://zoobank.org/urn:lsid:zoobank.org:pub:FFCB8A36-1CE1-4D5F-90D7-A5D773CF121B

Xenungulates是一种独特的双齿类有蹄类动物，在古新世和始新世早期遍布南美。在这里，我们描述，说明和分析一种新的Xenungulata，Rodcania kakan gen。等。十一月，这是来自阿根廷低纬度地区的第一个。从RíoLoro地层（Tucumán省）中发现了该地层，据估计其古新世年龄。该材料包括一个左牙的碎片，该碎片的牙釉质表面不完整，侵蚀了牙釉质，而牙釉质几乎完整，侵蚀了牙龈。这两颗牙齿都与Xenungulata坚固的珐琅质，垂直取向的Hunter–Schreger束带（HSB）共享，并沿远端倾斜。罗堪尼亚与其他xenungulate的区别在于m3三角体，简化且近中距短；没有副甲胎; 相对于近中胫骨轴和原先的刚毛的斜生肌更倾斜的原虫体，指向原胚体的位置；并且有更宽和更长的距骨。对13个物种和36个颅齿特征进行了系统发育分析，结果发现卡坎河R. kakan是Carodniidae的基础成员，在四个最简约的树中有10个亚同形体。RíoLoro动物区系和其余Xenungulate分类群的体重估计显示，R。k​​akan是RíoLoro组合中最大的哺乳动物，重约165千克，大小可与Carodnia feruglioi媲美。。体重的增加与xenungulates的进化趋势没有明确的关系。

http://zoobank.org/urn:lsid:zoobank.org:pub:FFCB8A36-1CE1-4D5F-90D7-A5D773CF121B