Synonym Parastrombidium Borror, 1972 (ref. ID; 2014); Pseudostrombidium Horvath, 1933 (ref. ID; 2014)
[ref. ID; 2014]
Elongate, narrow, dorso-ventrally flattened body, tapering to a pointed tail. The AZM relatively small (quarter body length). 2 rows of marginal cirri joining posteriorly. Typical arrangement of fronto-ventral and transverse cirri. With or without caudal cirri. Macronucleus in two parts. Few species have been described.
Borror (1972) submerged this genus in Oxytricha. Jankowski (1979) retains it in Kahl's (1932) subgeneric status.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)
[ref. ID; 4751]
Type species; Urosoma cienkowski (ref. ID; 4751)
[ref. ID; 4894]
Improved characterization; Adoral zone of membranelles and undulating membranes in Gonostomum pattern. Frontoventral cirri arranged in a row with anterior cirrus usually slightly displaced to left. Postoral ventral cirri in dense cluster underneath buccal vertex. Two pretransverse ventral and five transverse cirri. One right and one left row of marginal cirri. Four dorsal kineties. Caudal cirri present. Primary primordia. Dorsal morphogenesis in Urosomoida pattern. (ref. ID; 4894)
Remarks; Most species assigned to this genus are slender and posteriorly more or less distinctly narrowed. However, the only autapomorphy we could find is the arrangement of the frontoventral cirri. The same pattern occurs in some species originally assigned to the genera Perisincirra (P. similis Foissner, 1982) and Hemisincirra (H. polynucleata Foissner, 1984). This character and the agreements in the oral apparatus and dorsal infraciliature indicate that they might belong to Urosoma, although the FVT cirri underneath the adoral zone are partially or completely reduced. Very likely, P. similis and H. polynucleata form a distinct clade in Urosoma. Alive and in protargol slides, Urosoma is easily distinguished from all genera of the subfamily Stylonychinae by the short (< 30% of body length) adoral zone of membranelles and the slender body. (ref. ID; 4894)
Type species; Urosoma cienkowskii Kowalewskiego, 1882 (by monotypy) (ref. ID; 4894)