Phylogenetic and Taxonomic Revision of an Enigmatic Group of Haptorian Ciliates, with Establishment of the Kentrophyllidae fam. n. (Protozoa, Ciliophora, Litostomatea, Pleurostomatida)

Haptorian ciliates in the closely similar genera Kentrophyllum and Epiphyllum possess a unique pattern of ciliature and are distinguished from one another only by the presence or absence of cytoplasmic spines projecting from the margin of the cell. Phylogenetic analyses based on SSU rDNA sequences of three new samples from coastal habitats in China revealed that species in the two genera clustered together indiscriminately (i.e. forms of neither genus clustered into an independent clade) as a maximally supported, monophyletic clade that branches basally to all other clades in the order Pleurostomatida and is strongly divergent from other members of the family in which the genera have been placed. As a result, we propose that Epiphyllum be synonymized with Kentrophyllum and that a new family Kentrophyllidae fam. n. be established for the genus. We hypothesize that the two-sutures of Kentrophyllum is a plesiomorphy within the Pleurostomatida and the unique peripheral kinety might represent an autapomorphy of Kentrophyllum. In addition, we provide a taxonomic revision of Kentrophyllum including description of three new species (K. bispinum sp. n., K. strumosum sp. n., and K. qingdaoense sp. n.), redescription of K. verrucosum (Stokes, 1893) Petz et al., 1995, and three new combinations (K. soliforme (Fauré-Fremiet, 1908) comb. n., K. hohuensis (Wang and Nie, 1933) comb. n. and K. shenzhenense (Pan et al., 2010) comb. n.). The surface ultrastructure of the genus Kentrophyllum is recorded for the first time. And a key to all known species of Kentrophyllum was also suggested.