Cyclocoelum microcotyleum, Noble, 1933

Dronen, Norman O. & Blend, Charles K., 2015, Updated keys to the genera in the subfamilies of Cyclocoelidae Stossich, 1902, including a reconsideration of species assignments, species keys and the proposal of a new genus in Szidatitreminae Dronen, 2007, Zootaxa 4053 (1), pp. 1-100 : 16

C. microcotyleum Noble, 1933

Type host. American coot, Fulica americana Gmelin ( Gruiformes : Rallidae ).

Type locality. Stockton, California, USA.

Remarks. This species was considered a synonym of C. pseudomicrostomum Harrah, 1922 by Bashkirova (1950) and of C. mutabile ( Zeder, 1800) by Dubois (1959). It is very similar to C. pseudomicrostomum and C. obscurum ( Leidy, 1887) , except that unlike C. microcotyleum , these two species appear to have a rudimentary oral sucker ( Harrah 1922) and lack a ventral sucker. Cyclocoelum microcotyleum Noble, 1933 was described by Noble (1933) as lacking an oral sucker (“no trace of an oral sucker”), but it was shown in histological sections to have a “vestigial” ventral sucker—Noble (1933).