Morphological and molecular analyses of the genera Peltidocotyle Diesing 1850 and Othinoscolex Woodland 1933, and a morphological study of Woodlandiella Freze, 1965 (Eucestoda, Proteocephalidea), parasites of South American siluriform fishes (Pimelodidae).

Morphological studies of type-species of the genera Peltidocotyle Diesing, 1850 and Othinoscolex Woodland, 1933 showed that these genera are synonyms. We therefore redescribe the type and fresh material of Peltidocotyle rugosa Diesing, 1850 and P. lenha (Woodland, 1933) [= Othinoscolex lenha Woodland, 1933], which appears to constitute two distinct species. They differ in the number and number of layers of testes, the diameter of the metascolex and the field occupied by the vitelline follicles. Phylogenetic analyses based on partial DNA sequences of 16S rDNA, 5.8S-ITS2 and 28S rDNA support these results. P. lenha and Woodlandiella myzofer (Woodland, 1933) are considered conspecific following a thorough morphological examination. With regard to host-parasite relationships, P. lenha has been reported from two host species, which is unusual as South American proteocephalideans generally display an oioxenous type of host-specificity.