Abstract
The cortical development of Diophryopsis hystrix, a small marine euplotid ciliate, was observed during binary division. The pattern of morphogenesis is generally similar to that of other Diophrys-like species, with the exception of the marginal cirrus, which develops in a unique manner in D. hystrix being formed from the posterior end of the dorsal kinety anlage, in a similar manner to the formation of the caudal cirri. In the small subunit (SS) rRNA gene sequence tree, Diophryopsis represents a distinct clade separate from Diophrys. Furthermore, our ontogenetic and SSrRNA gene sequence data both support the suggestion that the Diophrys complex is sister to Uronychia, and should be considered as a distinct subfamily within the family Uronychiidae, i.e. Diophryinae Jankowski, 1979, comprising Diophrys, Diophryopsis, and Paradiophrys. Diagnoses of the subfamilies Diophryinae and Uronychiinae are provided.