Cestoplanoida Faubel, 1983, a poorly known monotypic genus within Cestoplanidae Lang, 1884, characterized by multiple female copulatory apparatuses, was previously known only from C. polypora (Meyer, 1921). We describe a second species, C. wanlitongensis sp. nov., from the intertidal zone of Pingtung County, southern Taiwan. It resembles C. polypora in external morphology and copulatory apparatuses but differs in having the pharynx in the posterior quarter rather than the posterior third of the body. Histological examination reveals protandrous sequential hermaphroditism and the absence of Lang’s vesicle, which is also absent in C. polypora based on a reassessment of its original description. This observation prompts the exclusion of Lang’s vesicle from the genus diagnosis. Phylogenetic analysis of partial 28S rDNA sequences tentatively places C. wanlitongensis sp. nov. as sister to Eucestoplana Faubel, 1983, within a strongly supported monophyletic clade representing Cestoplanidae. This study expands the taxonomic and molecular knowledge of Cestoplanoida, revises the generic diagnosis, and contributes to understanding the phylogenetic relationships within Cestoplanidae, providing a framework for future systematic and evolutionary studies.
Cotylea, Cestoplanidae, Multiple female apparatuses, Molecular phylogeny, Maximum likelihood
