Two names, one species: redescription and phylogenetic position of Freitas, 1959 provides new insights into the evolutionary history of the Cosmocercidae.

are gastrointestinal parasites of anurans, distributed throughout Central and South America. and are some of the most commonly reported species parasitising anurans from Brazil, and the morphological differences between them are unclear. In the present study, we redescribed based on a re-examination of type series and newly collected material from the frog in the state of Amapá, Brazil. Additionally, we re-examined the type series of , and propose it as a junior synonym of . We provide detailed morphological and morphometric data with intraspecific variation analyses and new molecular data for . In the present phylogeny, formed a well-supported clade with sp. and . Based on molecular phylogenetic analyses and some morphological similarities, our findings support the hypothesis that is a member of the family Cosmocercidae, not Atractidae. Additionally, we provide the first ultrastructural descriptions of , and establish the species' phylogenetic position from the Cosmocercidae.