Grupo de Estudios en Biodiversidad, Escuela de Biología, Universidad Industrial de Santander, Carrera 27 # 9, Bucaramanga, Santander, Colombia..
Zootaxa. 2021 Feb 2;4920(4):zootaxa.4920.4.1. doi: 10.11646/zootaxa.4920.4.1.
Neacomys Thomas, 1900 is an oryzomyine genus comprising at least 17 lineages distributed from easternmost Panama to northern Bolivia. As is the case for other groups of the subfamily Sigmodontinae, Neacomys have experienced a substantial increase in the rate of species descriptions in the last two decades, prompted by the progressive generation of morphological, molecular and karyological data. Nevertheless, most of the studies related to the genus have focused on the assessment of Cis-Andean populations, so that the Trans-Andean ones have been relegated to the background. In more than a century, only two species have been described from that region, one of them present in Colombia (N. tenuipes Thomas, 1900). Here, a new species of Neacomys is named and described based on samples collected in montane ecosystems of the Serranía de los Yariguíes, an isolated massif in the Magdalena Valley (Trans-Andean Colombia). Its validity is supported by a unique combination of morphological and molecular characters: Neacomys sp. nov. can be distinguished from other congeners mainly by the presence of broad ochraceous-orange patches on the sides of the muzzle, a gray-based ochraceous buff ventral fur, a thick hamular process of the squamosal, an opened ectotympanic ring, and a narrow anterocone of M1. The species is recovered as a clearly divergent and well-supported monophyletic group in the phylogenies, which implies it is not closely related to any other species in the genus and probably represents an early radiation within it. The new species of Neacomys constitutes the only rodent described from Colombia in more than 50 years and brings the list of mammals of the country to 529 species. Its discovery evidences that Trans-Andean region could be an important source of hidden diversity for the genus, and in Colombia, for rodents in general. Thus, further inventories, especially into remote areas, are needed to unveil this diversity. The fact that the new species seems to be endemic to an isolated mountain range implies it merits attention in terms of conservation.
托马斯新沙鼠（Neacomys Thomas，1900）是一个至少包含 17 个谱系的稻鼠属，分布范围从最东端的巴拿马到玻利维亚北部。与其他细尾鼠亚科（Sigmodontinae）的群体一样，由于形态学、分子学和染色体数据的不断发展，在过去的二十年中，对新沙鼠的物种描述数量大幅增加。然而，与该属有关的大多数研究都集中在评估安第斯山脉中部的种群，以至于安第斯山脉南部的种群被忽略了。在一个多世纪的时间里，只有两种新沙鼠从该地区被描述出来，其中一种存在于哥伦比亚（N. tenuipes Thomas，1900）。在这里，根据在 Magdalena 山谷（哥伦比亚安第斯山脉南部）孤立山脉的 Serranía de los Yariguíes 山地生态系统中采集的样本，命名并描述了一种新的新沙鼠。它的有效性得到了独特的形态学和分子特征的支持：Neacomys sp. nov. 可以主要通过口鼻部两侧宽阔的橙黄色斑块、灰色基底的橙黄色软毛腹部皮毛、厚实的鳞骨的叉骨突、开放的鼓室环以及 M1 的狭窄前尖峰来与其他近缘种区分开来。该物种在系统发育中作为一个明显分化且得到很好支持的单系群被回收，这意味着它与属中的任何其他物种都没有密切关系，可能代表了属内的早期辐射。新的新沙鼠物种是 50 多年来唯一从哥伦比亚描述的啮齿动物，使该国的哺乳动物物种数量达到 529 种。它的发现表明，安第斯山脉南部地区可能是该属隐藏多样性的重要来源，在哥伦比亚，也是一般啮齿动物的重要来源。因此，需要进行进一步的清查，特别是对偏远地区进行清查，以揭示这种多样性。新物种似乎是孤立山脉特有的事实意味着它在保护方面值得关注。
