This study reports Peruvian freshwater species of Stenostomum (Catenulida) from the upper Yurúa River of the Amazon Basin. A total of 11 species were found. One of them, Stenostomum ashanika, sp. nov., is described. It can be distinguished by: a pre-pharyngeal constriction; a small cauda; a small, rounded, mobile and ventrally directed pharynx; and a tri-radiate mouth. The remaining 10 species are reviewed and illustrated; eight are first records for Peru. A preliminary phylogenetic analysis of neotropical stenostomid species based on morphological data is undertaken, including all Rhynchoscolex, Stenostomum and Myostenostomum species described for the area. The Rhynchoscolex species are basal and paraphyletic; the species of Myostenostomum are monophyletic, within the Stenostomum clade, supported by the presence of a muscular gizzard in the anterior region of the intestine. Ciliated pits and rhabdoids are synapomorphies of the Stenostomum + Myostenostomum clade. This is the first morphological study of the relationships between stenostomid species. The most relevant characters in the phylogenetic analysis are those related to cerebral brain lobes. The results also show that many of the morphological characteristics of the species under study are poorly known and should be studied in more depth.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.