Three closely-related subclasses Phacodiniidia Small & Lynn, 1985, Protohypotrichia Shi et al., 1999, and Euplotia Jankowski, 1979 (Protista, Ciliophora): A new contribution to their phylogeny with reconsiderations on the evolutionary hypotheses.

The huge variety of species and worldwide distribution of ciliated protists in class Spirotrichea continue to make it one of the most complicated and confused groups in Ciliophora, despite significant research interest in the unique molecular genetics of these organisms. In this study, the morphological and molecular information were integrated, and it is inferred from a new perspective for the evolutionary relationship among Phacodiniidia, Protohypotrichia, Hypotrichia and Euplotia. Our results indicate that Kiitricha and Caryotricha, two members in Protohypotrichia, may represent two parallel branches of evolution; Euplotidae and Aspidiscidae represent the most recently diverged taxa within Euplotida, followed by Certesiidae, Gastrocirrhidae, and Uronychidae. Further, representative morphological characters (e.g. fronto-ventral-transverse cirral anlagen, undulating membranes, marginal cirri and caudal cirri) were stochastically mapped on phylogenies to speculate evolutionary path and morphological characters of the evolutionary transition node groups were assumed.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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