Arnal Michelle, Pérez María E
Affiliation: unknown; Email:
Zootaxa. 2013 Feb 19;3616:119-34. doi: 10.11646/zootaxa.3616.2.2.
Octodontoidea is the most speciose and ecologically diverse superfamily of caviomorph rodents. The systematic relationships of modern octodontoids is moderately accepted, however, the relationships of fossils (from the Eocene?-middle Miocene) are not clear. In recent years the hypothesis of a complex early evolution of the superfamily has emerged, with "basal octodontoids" representing different evolutionary lineages. The extinct family Acaremyidae may represent one such lineage, consisting of the genera Acaremys, Sciamys, Galileomys, and variably Platypittamys. In this work we describe a new octodontoid rodent recorded in post-Colloncuran? levels exposed at the locality of El Petiso, Northwest of Chubut Province, Argentina. Based on a systematic analysis of dental characters, we conclude that the new specimens correspond to a new species of Sciamys. Additionally, if the post-Colloncuran age for El Petiso is verified, the new species will extend the temporal range of the family Acaremyidae until, at least, the late middle Miocene, as well as the temporal range for the genus Sciamys from the Santacrucian SALMA. Our phylogenetic analyses corroborate the position of the new species as a member of Sciamys, and confirm that Acaremyidae represents an extinct family from Patagonian South America that lived until the middle Miocene. Massoiamys obliquus qualifies as morphological ancestor that pre-announces the octodontiform tooth pattern of octodontids. Thus, the octodontiform tooth pattern appears at least twice within the superfamily Octodontoidea.
八齿鼠总科是豚鼠型亚目啮齿动物中物种最丰富、生态多样性最高的总科。现代八齿鼠类的系统发育关系已得到一定程度的认可，然而，化石（始新世？—中新世中期）的关系尚不清楚。近年来，出现了关于该总科早期复杂进化的假说，“基础八齿鼠类”代表不同的进化谱系。已灭绝的阿卡罗鼠科可能代表这样一个谱系，包括阿卡罗鼠属、科学鼠属、伽利略鼠属，以及分类存在变化的宽齿鼠属。在这项研究中，我们描述了一种新的八齿鼠类啮齿动物，它记录于阿根廷丘布特省西北部埃尔佩蒂索地区出露的后科隆库兰阶地层中。基于对牙齿特征的系统分析，我们得出结论，新标本属于科学鼠属的一个新物种。此外，如果埃尔佩蒂索地区的后科隆库兰阶时代得到证实，这个新物种将把阿卡罗鼠科的时间范围至少扩展到中新世中期晚期，同时也将科学鼠属的时间范围从圣克鲁斯期南美陆生哺乳动物时代扩展。我们的系统发育分析证实了新物种作为科学鼠属成员的地位，并确认阿卡罗鼠科是来自巴塔哥尼亚南美洲的一个已灭绝科，生存至中新世中期。斜纹大原鼠可被视为预示八齿鼠科八齿型齿模式的形态学祖先。因此，八齿型齿模式在八齿鼠总科内至少独立出现了两次。
