A new acaremyid rodent (Caviomorpha, Octodontoidea) from Scarritt Pocket, Deseadan (late Oligocene) of Patagonia (Argentina)

ABSTRACTOctodontoidea is the most diverse caviomorph clade presently represented in South America by Octodontidae, Echimyidae, and Abrocomidae. Some evidence suggests that in the past they were taxonomically even more diverse, including several independent lineages with no modern representatives, sometimes considered as families. One of them is Acaremyidae, known until now from the Colhuehuapian-Colloncuran (early to early-middle Miocene) of Patagonia. Here we describe a new octodontoid rodent from the Deseadan (late Oligocene) of Scarritt Pocket (Patagonia): <i>Changquin woodi</i>, gen. et sp. nov. Cladistic analysis indicates that the new species is an acaremyid related to the Santacrucian (early Miocene) <i>Sciamys</i>. Acaremyidae was recovered as a monophyletic group. <i>C. woodi</i>, gen. et sp. nov., the oldest representative of Acaremyidae, extends the family biochron back to the late Oligocene, and indicates that acaremyids differentiated before the Deseadan. <i>C. woodi</i> represents the first Deseadan octodontoid displaying protohypsodont cheek teeth, showing that the Deseadan was a period of important diversification for octodontoids, as it was for the cavioids. <i>C. woodi</i> adds a new element to the faunal differences observed between Patagonian and Bolivian Deseadan faunas. A new U-Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) date (27.17 ± 0.54 Ma) for Scarritt Pocket is provided.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP

摘要：八齿鼠总科（Octodontoidea）是目前南美洲多样性最高的豚鼠形演化支，现生类群涵盖八齿鼠科（Octodontidae）、棘鼠科（Echimyidae）与绒鼠科（Abrocomidae）。多项研究证据表明，该类群在地质历史时期的分类多样性更为丰富，曾包含多个无现生代表的独立演化支系，部分类群曾被独立设立为科。尖齿鼠科（Acaremyidae）便是其中一类，此前仅在巴塔哥尼亚的Colhuehuapian-Colloncuran阶（早中新世至早-中中新世）地层中有发现记录。本次研究记述了一件采自巴塔哥尼亚斯克里特口袋（Scarritt Pocket）德塞德阶（晚渐新世）地层的八齿鼠总科啮齿类新物种：*Changquin woodi*，新属新种（gen. et sp. nov.）。支序分类分析结果显示，该新种属于与早中新世圣克鲁斯阶的*Sciamys*亲缘关系较近的尖齿鼠科类群；尖齿鼠科被恢复为单系类群。*C. woodi*，新属新种作为尖齿鼠科目前已知最古老的代表，将该科的生物地层延限推至晚渐新世，表明尖齿鼠科的分化发生在德塞德阶之前。*C. woodi*是首个发现于德塞德阶的具有前高冠颊齿的八齿鼠总科物种，这一发现表明德塞德阶时期八齿鼠总科经历了重要的演化辐射，与豚鼠总科（cavioids）的演化历程一致。*C. woodi*为巴塔哥尼亚与玻利维亚德塞德阶动物群之间的群落差异增添了新的佐证。本次研究还提供了斯克里特口袋地层的新U-Pb激光剥蚀电感耦合等离子体质谱（LA-ICPMS）测年数据：27.17 ± 0.54 Ma。补充数据：本文的补充材料可通过http://www.tandfonline.com/UJVP 免费获取。