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The morphology, infraciliature and morphogenesis of the marine hypotrichous ciliate, Thigmokeronopsis rubra sp. nov., collected from the coastal waters off Qingdao (Tsingtao), China, were studied in vivo and following protargol impregnation. Compared with the known Thigmokeronopsis species, T. rubra is distinguished by its elongated fusiform body shape, in vivo about 140-200 µm long with two kinds of granules, pale yellow-green and red, respectively; 11-16 frontal, two frontoterminal, one buccal and ca seven transverse cirri; usually 7-11 left postoral ventral files; two mid-ventral rows comprising a total of ca 51 cirri; 30-49 left and 28-45 right marginal cirri; three complete dorsal kineties. The morphogenetic process can be summarized as follows: (1) an anarchic field originates independently between the left mid-ventral cirri and the left postoral ventral files and generates the opisthe's adoral membranelles, undulating membranes, frontoventral and transverse cirri; (2) the proter's oral primordium originates apokinetally to the left of the undulating membranes and develops on the bottom and right walls of the buccal cavity producing the new undulating membranes and adoral membranelles; (3) the fronto-ventral transverse anlage (FVT-anlage) originates independently near the anterior left mid-ventral cirri in the proter; (4) the marginal rows and dorsal kineties originate de novo in both dividers; (5) the old structures do not participate in the formation of the new ones and are eventually replaced; (6) the macronuclear nodules fuse completely forming a single branched mass prior to division. [ABSTRACT FROM AUTHOR]