A new species of small-bodied sparassodont (Mammalia, Metatheria) from the middle Miocene locality of Quebrada Honda, Bolivia

ABSTRACTThe Sparassodonta (Mammalia, Metatheria) are a group of carnivorous mammals that dominated the macropredatory guild of South America during the Cenozoic. Here, we describe a new sparassodont based on a single specimen from the middle Miocene Quebrada Honda local fauna of southern Bolivia. This specimen (UF 27881) does not clearly correspond to any major sparassodont group (e.g., Hathliacynidae, Borhyaenidae, etc.) and represents a morphotype previously unknown among the Sparassodonta. UF 27881 is distinguished from other sparassodonts by its short, broad, borhyaenid-like rostrum and small size, among other features. However, we decline to coin a new name for UF 27881 due to the fragmentary nature of this specimen and the absence of most of its dentition. This specimen suggests that the appearance of the Sparassocynidae and several hypercarnivorous didelphid taxa (including <i>Thylophorops</i>, <i>Thylatheridium</i>, <i>Lutreolina</i>, and <i>Hyperdidelphys</i>) represent an evolutionary response to the decline in small, predatory sparassodont taxa during the late Cenozoic. This study documents new morphological diversity among the Sparassodonta and highlights the value of fossils from traditionally undersampled parts of South America.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP.

摘要：袋犬目（Sparassodonta，哺乳纲Mammalia、后兽亚纲Metatheria）是一类食肉哺乳类，在新生代时期主导了南美洲的宏捕食者生态类群。本文记述了一件产自玻利维亚南部中中新世洪达谷（Quebrada Honda）本地动物群的单个新袋犬目标本。该标本（编号UF 27881）无法明确归入任何已知的主要袋犬目类群（如哈氏袋犬科（Hathliacynidae）、袋鬣狗科（Borhyaenidae）等），代表了袋犬目内此前未被发现的形态类型。除其他特征外，该标本以其短宽且类似袋鬣狗科的吻部与较小的体型，区别于其他袋犬目类群。但鉴于该标本保存残缺且大部分齿系缺失，我们未为其建立新的分类名称。该标本表明，袋犬科（Sparassocynidae）与若干超食肉性负鼠类群（包括Thylophorops、Thylatheridium、Lutreolina以及Hyperdidelphys）的出现，是新生代晚期小型捕食性袋犬目类群衰落的演化响应。本研究揭示了袋犬目新的形态多样性，并凸显了南美洲传统采样不足地区化石的研究价值。
补充数据：本文的补充材料可免费从http://www.tandfonline.com/UJVP 获取。