ABSTRACT

We provide a new morphological description of the holotype and a previously undescribed large sample of the type species of the genus Copemys Wood, 1936, Copemys loxodon (Cope, 1874a), a Miocene North American cricetid rodent occasionally treated as the ancestor of the non-arvicoline cricetids (i.e., neotomines, sigmodontines, and tylomyines). Dental, mandibular, and skull morphology is described from material recovered in a quarry in the vicinity of the type locality in the Española Valley of New Mexico, U.S.A. Copemys loxodon is a small, brachydont cricetid characterized by a mandible with a large mental foramen lateral in position and an enlarged retromolar fossa; the skull having wide infraorbital foraminae and robust zygomatic arches; and the upper molars being pentalophodont, the lower molars tetralophodont. The procingulum of the M1 has two conules, an enamel atoll is present on the M2, and the procingulum of m1 is composed exclusively of the lingual conulid. Preliminary comparisons among representatives of the 11 species of Copemys suggest that some forms currently recognized as Copemys probably do not belong to that genus, as indicated both by our results and those of other recent studies. Understanding the limits of variation in the type species of Copemys provides a starting point for the development of a more detailed phylogenetic analysis of early North American cricetids and their possible descendants.

摘要

我们提供了新的全形形态学描述，以及以前未描述的Copemys Wood属（1936年），Copemys loxodon（Cope，1874a）等类型物种的大样本，这是中新世北美洲的ice骨啮齿类动物，偶尔被视为非阿维考林酯（即，新毒素，西格莫定和蒂洛米因）。从美国新墨西哥州埃斯帕尼奥拉山谷典型地区附近采石场中回收的材料中描述了牙齿，下颌骨和颅骨的形态是一种短的，近距离的ice骨，其特征是下颌骨具有侧向位置的较大的精神孔，并具有扩大的后磨牙窝。头骨具有宽的眶下孔和坚固的弓。上臼齿为五齿齿，下臼齿为四齿齿。M1的程序有两个视锥，M2上有一个釉质环礁，而m1的程序仅由舌状舌状体组成。对11个Copemys物种的代表进行的初步比较表明，正如我们的结果和其他近期研究所表明的那样，目前公认的Copemys的某些形式可能不属于该属。了解Copemys类型物种的变异极限 为北美早期ice骨科及其可能后代的更详细的系统发育分析的发展提供了起点。