Investigating the psammophilic karyorelictean ciliate families Kentrophoridae and Cryptopharyngidae (Protista, Ciliophora): molecular phylogeny, geographic distributions and a brief revision including descriptions of a new genus, a new species and a

Psammophillic ciliates are an integral part of the foodweb despite being underrepresented in terms of molecular phylogeny and modern taxonomy. To investigate the karyorelictean group, sampling was conducted in interstitial marine habitats in China for ciliates living between the sand grains, resulting in an examination of the families Cryptopharyngidae Jankowski, 1980 and Kentrophoridae Jankowski, 1980. Three species, i.e., <i>Cryptopharynx setigerus</i> Kahl, 1928, <i>Kentrophoros fasciolatus</i> (Sauerbrey, 1928) Foissner, 1995 and <i>K. fistulosus</i> (Fauré-Fremiet, 1950) Foissner, 1995, are clearly recognized as being cosmopolitan, while other species await further recording. Phylogenetic analyses were carried out based on updated data. These revealed that the families Cryptopharyngidae and Kentrophoridae are closely related, and most genera studied are monophyletic, although <i>Cryptopharynx qingdaoensis</i> n. sp. is located within the Kentrophoridae branch. Brief revisions of two genera, namely <i>Cryptopharynx</i> Kahl, 1928 and <i>Kentrophoros</i> Sauerbrey, 1928, are provided including keys to the identification of nine species belonging to the former and 12 species belonging to the latter. One new genus, <i>Parakentrophoros</i> n. gen., and one new species, <i>Cryptopharynx qingdaoensis</i> n. sp., are described and a new combination, <i>Parakentrophoros canalis</i> (Wright, 1982) n. comb., is established. Finally, it appears that the subapical oral apparatus undergoes a gradual degeneration process from Cryptopharyngidae to Kentrophoridae.