Date of this Version
Van Haitsma (1925) created the genus Crassiphiala for C. bulboglossa Van Haitsma with the following diagnosis :-Diplostome parasites with bisegmented body, vitelline follicles restricted to hind body, acetabulum rudimentary or absent.
Even though Hemistomum denticulatuwa Rudolphi, 1819 had a well developed acetabulum it so closely resembled C. bulboglossa in all other respects that Dubois (1933) transferred it to the genus Crassiphiala. Hunter (1933), while including under Crassiphiala another species, Hemistomum ambloplitis Hughes, 1927, a form possessing a well developed acetabulum, amended the generic diagnosis to include forms possessing a well developed acetabulum.
Yamaguti (1934) created the genus Uvulifer with U. gracilis as the type species. Although U. gruilis resembled members of the genus Crassiphiala, the new genus differed in the presence of a well developed acetabulum (smaller than the oral sucker), and the presence of a dorso-terminal sucker-like genital atrium which terminated in an uvula-like muscular appendage. At the same time he created the genus Pseudodiplostomum, distinguishing it from Uvulifer by the fact that the acetabulum was larger than the oral sucker and the uvula-like muscular appendage or genital bulb in the genital atrium was absent. Harwood (1936) amended Hunter's diagnosis of Crassiphiala so as to include both Uvulifer and Pseudodiplostomum as synonyms of Crassiphiala, transferring the type species of the two genera to the genus Crassiphiala. After a comprehensive study of the group Dubois (1938) came to the conclusion that the presence of a well developed acetabulum whether smaller or larger than the oral sucker is a suitable character for the separation of some genera included under the sub-family Crassiphialini Dubois 1936. He, accordingly, recognized the validity of Yamaguti's two genera, Uvulifer and Pseudodiplostomum. Pande (1938) added a species to the genus Crassiphiala, C. stunkardi. On closer examination this species is believed to be more closely related to the genus Uvulifer, and accordingly is removed to that genus.