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During a study on the diversity of ciliated protists in Lake Weishan Wetland, the largest wetland in northern China, four epibiotic sessilid peritrichs were isolated from aquatic host animals. Two of them, i.e., Epistylis cambariKellicott, 1885 and Epistylis lwoffiFauré-Fremiet, 1943, were known species whereas the other two, i.e., Parapiosoma typicumgen. nov., sp. nov. and Orborhabdostyla gracilissp. nov., are new to science. The new genus Parapiosomagen. nov. is characterized by its branched non-contractile stalk, everted peristomial lip, obconical macronucleus and transverse silverlines. Two species are assigned to the new genus, namely Parapiosoma typicumsp. nov. and Parapiosoma gasterostei(Fauré-Fremiet, 1905) comb. nov. Morphologically, P. typicumsp. nov. is recognized by its goblet-shaped zooids, single-layered peristomial lip, dichotomously branched stalk, and infundibular polykinety 3 (P3) containing three equal-length rows. Orborhabdostyla gracilissp. nov. is characterized by its slender zooid, curved macronucleus, and three equal-length rows in infundibular P3. Improved diagnoses and redescriptions of E. cambariand E. lwoffiare provided including, for the first time, data on the ciliature of E. cambari. Phylogenetic analyses based on SSU rDNA, ITS1-5.8S rDNA -ITS2, and LSU rDNA sequence data strongly support the assertion that the family Epistylididae comprises morphospecies with different evolutionary lineages and indicate that Parapiosomagen. nov. may represent a new taxon at family level.

The ciliate genus Pleuronemacomprises approximately 30 nominal species and has been reported in freshwater, brackish water, and marine habitats. Nevertheless, recent studies have indicated that there might be a large undiscovered species diversity. In the present work, four new Pleuronemaspecies, namely P. foissnerisp. nov., P. parasmallisp. nov., P. parasalmastrasp. nov., and P. paraorientalesp. nov., collected from Shenzhen, southern China, was investigated using taxonomic methods. The diagnosis, description, comparisons with morphologically related species and detailed morphometric data are supplied for each. The small subunit ribosomal RNA (SSU rRNA) gene of the four new species is sequenced and their molecular phylogeny is analyzed. The SSU rRNA gene tree shows that Pleuronemais polyphyletic comprising several separate clades. All four new species cluster consistently with P. orientaleKF206429, P. puytoraciKF840520 and P. setigerumFJ848874 within the core Pleuronematidae + Peniculistomatidae clade. Phylogenies of Pleuronematidae-related taxa are also discussed.