Abstract Based on two adult specimens collected in the Río León (Azuay, Ecuador), we describe a new highland species of a small crab-eating rat of the genus Ichthyomys Thomas (Rodentia, Cricetidae, Ichthyomyini). It is distinguishable from Ichthyomys hydrobates (Winge, 1891), the species phenetically closest to it, by its smaller size, bicolored tail (unicolored in I. hydrobates), broad and heavily fringed hindfoot (narrower and moderately fringed in I. hydrobates), and several craniodental traits (e.g. rostrum short broad; nasals anteriorly truncated; interorbital region narrow; supraorbital margins smoothly rounded; supraorbital foramina small, zygomatic plate very narrow; incisors opisthodont; length of M3 half that of M2). The new species occurs in the western Andes in southern Ecuador and is allopatric with Ichthyomys stolzmanni Thomas, 1893, which also has a bicolored tail but is larger. The new species brings the number of Ecuadorean Ichthyomys to four, Ecuador thus becoming the country with the greatest diversity of Ichthyomyini (four genera and eight species).

中文翻译：

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来自厄瓜多尔的一种新种的鱼蟹属食蟹鼠（啮齿目、仓鼠科、鼠科）

摘要基于在里奥莱昂（厄瓜多尔阿苏艾）采集的两个成年标本，我们描述了一种新的高原物种，一种新的高地物种，属于 Ichthyomys Thomas 属（啮齿类、仓鼠科、Ichthyomyini）的小型食蟹鼠。它与 Ichthyomys hydrobates (Winge, 1891) 不同，后者是表型上最接近它的物种，具有较小的尺寸、双色尾巴（在 I. hydrobates 中为单色）、后足宽且有大量流苏（在 I. hydrobates 中较窄且中等流苏），和几个颅牙特征（例如，喙短宽；鼻前截短；眶间区域狭窄；眶上缘光滑圆润；眶上孔小，颧骨板非常窄；门牙反齿；M3 的长度是 M2 的一半）。这个新物种出现在厄瓜多尔南部的安第斯山脉西部，与 Ichthyomys stolzmanni Thomas 异域分布，1893 年，它也有一个双色的尾巴，但更大。新物种使厄瓜多尔鱼鳞目动物的数量达到四个，厄瓜多尔因此成为鱼鳞鱼种类最多的国家（四属八种）。