Abstract

While hypsodonty mostly is associated with medium to large body sizes in sigmodontine rodents, high-crowned molars combined with small bodies rarely are recorded. This latter condition is present in Neomicroxus (Sigmodontinae, incertae sedis), a genus of high-Andean cricetids also characterized by a noticeable set of cranial traits, including enlarged turbinals and rostrum, slanting zygomatic plate, and a marked backward displacement of the vertical ramus of the dentary, linked with an enlargement of the basicranial region. These morphological features, combined with the isolated position of this lineage in molecular-based phylogenies, indicate that Neomicroxus should be situated in a new tribe. We name and describe this Páramo novelty monotypic clade here. As a working hypothesis, the hypsodonty displayed by this group is considered an evolutionary response to continued volcanic ash falls that characterized the region during the Neogene. A reappraisal of tribe recognition within the two cricetid largest subfamilies, arvicolines and sigmodontines, is made, coupled with a discussion about the role of morphological convergence in “long-nose” cricetids.

中文翻译：

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北部安第斯山脉帕拉莫斯的独特荒谬实验值得部落认可

摘要

尽管乙状结肠啮齿类动物的多齿症与中等到大体型有关，但是很少有人记录到高冠磨牙与小体型相结合。这后一种情况是存在于Neomicroxus（棉鼠亚科，地位未定），高斯cricetids特征还在于显着的组颅特征，包括放大turbinals和讲台，倾斜颧板的一个属，并且垂直支的一个标记向后位移牙齿的部分，与基本的颅骨区域的扩大有关。这些形态特征，再加上该谱系在基于分子的系统发育中的孤立位置，表明Neomicroxus应该位于一个新的部落中。我们在此命名并描述这个Páramo新奇单一类型的进化枝。作为一个可行的假设，该小组展示的催眠术被认为是对持续火山灰坠落的演化反应，而火山灰坠落是新近纪时期的特征。重新评估了两个最大的骨科动物亚族中的阿维克林和Sigmodontines，并讨论了形态融合在“长鼻”骨科动物中的作用。