The genus Oligoryzomys is the most speciose genus in the tribe Oryzomyini; however, under the general lineage concept of species, at least nine lineages are pending review and naming. In this study, I carry out qualitative and quantitative morphological analyses of specimens of Oligoryzomys andinus, O. aff. andinus, and O. arenalis, to delimit these three lineages. I show that O. aff. andinus is morphologically distinct both from O. andinus and O. arenalis, corroborating that the lineage merits recognition as a species, as suggested by previously published molecular analyses (Hurtado and D’Elía 2019). I therefore describe O. aff. andinus as a new species endemic to the Polylepis forests on the western slope of the Andes and coastal Lomas in central Peru. Finally, I propose two hypotheses about the biogeographical history of O. andinus, O. arenalis, and this new species.

中文翻译：

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来自秘鲁的一种新种Oligoryzomys (Rodentia: Cricetidae)

Oligoryzomys 属是 Oryzomyini 部落中最物种的属；然而，在物种的一般谱系概念下，至少有九个谱系有待审查和命名。在这项研究中，我对 Oligoryzomys andinus, O. aff 的标本进行了定性和定量的形态分析。andinus 和 O. arenalis 来划分这三个谱系。我展示了 O. aff。andinus 在形态上与 O. andinus 和 O. arenalis 不同，这证实了该谱系值得被认可为一个物种，正如先前发表的分子分析所表明的（Hurtado 和 D'Elía 2019）。因此，我描述了 O. aff。andinus是安第斯山脉西坡和秘鲁中部洛马斯沿海的Polylepis森林特有的新物种。最后，我提出了关于 O. andinus、O. arenalis 的生物地理历史的两个假设，