Proteocephalus brooksi n. sp. (Cestoda:Proteocephalidae) in the neotropical freshwater fish Rhamdia guatemalensis (Siluriformes: Pimelodidae) from Lake Catemaco, Veracruz, Mexico.

Proteocephalus brooksi n. sp. is described from the neotropical pimelodid fish Rhamdia guatemalensis from Lake Catemaco, Veracruz, México. The new species is characterized by the "paramuscular" position of vitellaria, the cortical origin of uterine stem with development of medullar lateral branches, the alternated position of vagina (anteriorly and posteriorly to cirrus sac), and the absence of apical organ and vaginal sphincter. Proteocephalus brooksi most closely resembles Nomimoscolex matogrossensis from which it differs in a series of characters. The probable paraphyletic nature of both Proteocephalus and Nomimoscolex and the convergent evolution of the "paramuscular" location of vitellaria among proteocephalideans are suggested, and the need for a phylogenetic analysis of the group is emphasized. The new species is assigned to Proteocephalus pending such an analysis.