Chiquito Elisandra Almeida, Percequillo Alexandre Reis
Laboratório de Mastozoologia e Biogeografia, Departamento de Ciências Biológicas, Centro de Ciências Humanas e Naturais, Universidade Federal do Espírito, Vitória, Espírto Santo, Brazil Laboratório de Mamíferos, Departamento de Ciências Biológicas, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, São Paulo, Brazil.
Zootaxa. 2019 Jan 25;4550(3):321-339. doi: 10.11646/zootaxa.4550.3.2.
Nectomys (Sigmodontinae, Oryzomyini) is currently composed by five species: Nectomys apicalis, N. magdalenae, N. palmipes, N. rattus, and N. squamipes. These rodents have strong morphologic adaptations to semiaquatic habit and inhabit forests along river and streams in almost the entire South American continent. Although Nectomys is not a very speciose genus, 23 nominal taxa are associated with this group. Among these names is Nectomys saturatus, described in 1897 and currently allocated as synonym of N. apicalis, the west-Amazon species of Nectomys. Based on the examination of type material of the genus Nectomys, we hypothesize that Nectomys saturatus is a valid species. To test this hypothesis, we examined morphological and morphometric traits of 570 specimens of genus Nectomys of the same age class, belonging to the five recognized species, including the N. saturatus type series. We analyzed the external dimensions through descriptive statistics and we assessed the variation in craniodental measurements by means of Discriminant Analysis. Our results indicate N. saturatus individuals are considerably larger than the samples of congeneric species in all external traits, and they were also discriminated from the other species in the multivariate space. Qualitatively, N. saturatus shows two exclusive traits, the presence of paralophule on M1 and almost parallel-sided interorbital region. In this sense, our set of evidences indicates that our hypothesis should be accepted and the name Nectomys saturatus represents a valid species.
水鼠属（棉鼠亚科，稻鼠族）目前由五个物种组成：尖吻水鼠、马格达莱纳水鼠、掌水鼠、鼠形水鼠和鳞足水鼠。这些啮齿动物对半水生习性具有很强的形态适应性，栖息在几乎整个南美大陆的河流和溪流沿岸的森林中。尽管水鼠属不是一个物种非常丰富的属，但有23个命名分类单元与该类群相关。其中包括1897年描述的饱和水鼠，目前被定为尖吻水鼠的同物异名，尖吻水鼠是水鼠属在亚马逊西部的物种。基于对水鼠属模式标本的研究，我们推测饱和水鼠是一个有效物种。为了验证这一假设，我们检查了570个同一年龄段的水鼠属标本的形态和形态测量特征，这些标本属于五个公认的物种，包括饱和水鼠的模式系列。我们通过描述性统计分析了外部尺寸，并通过判别分析评估了颅骨牙齿测量的变化。我们的结果表明，饱和水鼠个体在所有外部特征上都比同属物种的样本大得多，并且在多变量空间中也与其他物种区分开来。定性地说，饱和水鼠有两个独特的特征，即M1上有副嵴和眶间区域几乎平行。从这个意义上说，我们的一系列证据表明我们的假设应该被接受，饱和水鼠这个名称代表一个有效物种。
