Serpentirhabdias mexicanus n. sp. (Nematoda: Rhabdiasidae) is described from the lung of the nauyaca viper Bothrops asper in Puebla State, central Mexico. This new species is the fifth of the genus described having onchia. Among the species included in this group, the new species is morphologically closest to S. viperidicus and S. atroxi. However, it differs from both species mainly by having only one excretory gland (compared to two present in S. viperidicus and S. atroxi). In addition, S. mexicanus n. sp. can be separated of S. viperidicus by tail length, shape of vulval lips, geographic distribution and host species and from S. atroxi by body length, number of papillae in the cephalic region, as well as the host species and geographic distribution. In the present study, we propose the new species based on morphological, host spectrum and genetic evidence. Phylogenetic analysis indicated Serpentirhabdias as a monophyletic group, with two subgroups that are congruent with the presence/absence of onchia in the esophagostome, host association and other relevant morphological characters.

Serpentirhabdias 墨西哥n. sp。 （线虫纲：Rhabdiasidae）是从墨西哥中部普埃布拉州的诺亚卡毒蛇Bothrops asper的肺部描述的。这个新物种是所描述的具有onchia的属中的第五个。在该组包括的物种中，新物种在形态上最接近S. viperidicus和S. atroxi 。然而，它与这两个物种的不同之处主要在于只有一个排泄腺（与S. viperidicus和S. atroxi中存在两个排泄腺相比）。此外， S. mexicanus n。 sp。可以与S分开。 viperidicus通过尾长、外阴唇形状、地理分布和寄主种类来区分，而S. atroxi通过体长、头侧乳头的数量以及寄主种类和地理分布来区分。在本研究中，我们根据形态、宿主谱和遗传证据提出了新物种。系统发育分析表明蛇形杆属是一个单系类群，有两个亚类，这两个亚类与食管口中甲壳的存在/不存在、寄主关联和其他相关形态特征一致。