Cyclocoelidae Stossich, 1902

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 : 9

Family Cyclocoelidae Stossich, 1902

Diagnosis. Medium-sized to large flatworms, lanceolate, body often tapered anteriorly and rounded posteriorly. Oral sucker, if present, usually poorly developed. Acetabulum generally absent, but reported in some species. Mouth subterminal, prepharynx generally shorter than esophagus, ceca frequently simple, inner wall sometimes irregular, undulating in overall appearance in some species, united near posterior extremity to form characteristic cyclocoel. Testes oval to elongate, borders smooth or irregular, tandem to diagonal, rarely side by side, usually located near posterior end, but may be equatorial to preequatorial in some species. Genital pore near midline of body, prepharyngeal, pharyngeal or postpharyngeal. Cirrus sac present, enclosing seminal vesicle, extending posteriorly to level of posterior aspect of esophagus to immediately postbifurcal. Ovary oval to elongate, intertesticular, pretesticular or posttesticular, forming a triangle or in a straight line with testes. Uterus intercecal to extracecal, uterine seminal receptacle present in some species. Vitellarium follicular, ventral and somewhat lateral to ceca, vitelline fields reaching to, or beyond, cecal bifurcation anteriorly, confluent posteriorly or not. Excretory vesicle generally Y-shaped, branches extending anterior to level of pharynx or beyond, reticulate where known. Excretory pore usually somewhat subterminal opening on dorsal surface, may approach being terminal in some species. Life cycles, where known, utilize either freshwater or terrestrial snails, polyembryony produces tailless cercariae that encyst in either the rediae where they were produced or in the tissue of snails. Adults in body cavity, lungs, air sacs, nasal and infraorbital sinuses, or hypothalamus of birds.

Type genus. Cyclocoelum Brandes, 1892 .