Hamacreadium Linton, 1910

Martin, Storm B., Cutmore, Scott C., Ward, Selina & Cribb, Thomas H., 2017, An updated concept and revised composition for Hamacreadium Linton, 1910 (Opecoelidae: Plagioporinae) clarifies a previously obscured pattern of host-specificity among species, Zootaxa 4254 (2), pp. 151-187 : 153

Hamacreadium Linton, 1910

Synonyms. Olivacreadium Bilqees, 1976 .

Diagnosis. Body large, elongate linguiform, tapering anteriorly, bluntly rounded or emarginate posteriorly, widest at level of ventral sucker or testes. Tegument aspinose. Forebody less than one half, typically approximately one third, of total body length. Suckers unspecialised, oral about one third size of ventral. Pharynx about one third size of oral sucker. Pre-pharynx short, often not visible from ventral perspective. Oesophagus of medium length, thickwalled. Intestine bifurcates in mid-forebody into blind-ending caeca usually extending beyond testes. Testes two, inter-caecal, always oblique, left anterior to right, often abutting or nearly so, elliptical to wedge-shaped, smooth to indented. Cirrus-sac clavate to cylindrical, diagonal, sinuous or straight, usually commencing dorsal to anterior half of ventral sucker and never extending distinctly into hindbody. Internal seminal vesicle large and sinuous; pars prostatica prominent; ejaculatory duct long, muscular. Genital atrium short, inconspicuous. Genital pore always post-bifurcal and sinistral, usually ventral to caecum. Ovary inter-caecal, dextral, with three or four to many deep lobes, immediately anterior to left testis and separated from ventral sucker by uterine coils. Canalicular seminal receptacle distinct. Vitellarium follicular. Vitelline fields two, one dorsal, one ventral; ventral field restricted to and confluent in hindbody; dorsal field always entering forebody where it is sometimes confluent, sometimes interrupted at level of ventral sucker, anterior extent pre-bifurcal, bifurcal or distinctly post-bifurcal. Uterus intercaecal, restricted to anterior to gonads, approaching genital atrium diagonally right to left and to left of and then dorsal to cirrus-sac. Metraterm simple, originating alongside cirrus-sac. Distinct uterine coils often difficult to discern. Eggs operculated, elliptical, unfilamented, tanned, unembryonated in utero, usually numerous. Excretory vesicle simple, tubular, medial but gently sinuous, always extending into forebody; anterior extent immediately pre-bifurcal, immediately post-bifurcal or distinctly post-bifurcal. Excretory pore terminal. Type species Hamacreadium mutabile Linton, 1910 .