As presently recognized, Herpetodiplostomum is a small genus of proterodiplostomid digeneans parasitic in crocodilians. Most members of Cheloniodiplostomum, a genus of proterodiplostomids that parasitize chelonians, were originally placed within Herpetodiplostomum. The 2 genera were distinguished based on the presence/absence of papillae on the holdfast organ and anterior extent of vitellarium. Our study of Herpetodiplostomum and Cheloniodiplostomum revealed a lack of consistent morphological differences between the genera. Therefore, we consider Cheloniodiplostomum to be a junior synonym of Herpetodiplostomum. Recent molecular phylogenetic studies included a number of proterodiplostomid taxa; however, DNA sequence data are not available for any Herpetodiplostomum or Cheloniodiplostomum species. Herein, we describe a new Herpetodiplostomum species from Geoffroy's side-necked turtle Phrynops geoffroanus from Mato Grosso State, Brazil. The new species can be distinguished from other Herpetodiplostomum species based on the distribution of vitellarium, level of development of holdfast papillae, and ratio of prosoma:opisthosoma width, among other characters. We provide the first molecular phylogeny of the Proterodiplostomidae that includes a Herpetodiplostomum species. The limited geographic distribution of Herpetodiplostomum spp. within the geographic ranges of caimans suggests a secondary host switching event from crocodilians to chelonian definitive hosts in the evolution of Herpetodiplostomum.

正如目前公认的那样，Herpetodiplostomum是寄生在鳄鱼体内的 proterodiplostomid digeneans 的一个小属。多数成员Cheloniodiplostomum，proterodiplostomids的一属寄生于龟类，原本放置在Herpetodiplostomum。2 属的区分是基于在固定器官上的乳头的存在/不存在和卵黄体的前部范围。我们的研究Herpetodiplostomum和Cheloniodiplostomum透露缺少的属间一致的形态差异。因此，我们认为Cheloniodiplostomum是一个异名Herpetodiplostomum. 最近的分子系统发育研究包括许多原二聚体类群；然而，DNA序列数据不可用于任何Herpetodiplostomum或Cheloniodiplostomum物种。在此，我们描述了来自巴西马托格罗索州Geoffroy 侧颈龟Phrynops geoffroanus 的一种新Herpetodiplostomum物种。根据卵黄体的分布、固定乳头的发育水平、前体与后体宽度的比率等特征，可以将新种与其他Herpetodiplostomum种区分开来。我们提供了包括Herpetodiplostomum在内的Proterodiplostomidae的第一个分子系统发育物种。Herpetodiplostomum spp 的地理分布有限。在凯门鳄的地理范围内，表明在Herpetodiplostomum的进化过程中，发生了从鳄鱼到龟类终宿主的次要宿主转换事件。