Dollfusiella qeshmiensis n. sp. (Cestoda: Trypanorhyncha) from the cowtail stingray Pastinachus sephen (Forsskål) in the Persian Gulf, with a key to the species of Dollfusiella Campbell & Beveridge, 1994.

A new species of the genus Dollfusiella Campbell & Beveridge, 1994 is described from Pastinachus sephen (Forsskål) in the Persian Gulf. Dollfusiella qeshmiensis n. sp. is allocated to the genus Dollfusiella based on the possession of two bothria, prebulbar organs, a heteroacanthous typical armature with tightly spaced rows of hollow hooks, a basal swelling and a characteristic basal armature without prominent macrohooks. The presence of an enlarged external seminal vesicle in Dollfusiella qeshmiensis n. sp. distinguishes this species from D. michiae (Southwell, 1929), D. bareldsi (Beveridge, 1990), D. owensi (Beveridge, 1990), D. geraschmidti (Dollfus, 1974), D. angustiformis Schaeffner & Beveridge, 2013, D. hemispinosa Schaeffner & Beveridge, 2013, D. spinosa Schaeffner & Beveridge, 2013 and D. taminii Menoret & Ivanov, 2014. The new species is distinguished from the remaining species within the genus by a combination of the following morphological features: the number of testes per segment, the number of testis columns and the number of homeomorphous hooks per half spiral row in the metabasal region. In the most recent taxonomic key to the species of Dollfusiella, the presence or absence of enlarged, microscopically visible spinitriches on the scolex was used as the first distinguishing character dividing the congeners into two groups. Since the existence of visible microtriches on the scolex peduncle of D. vooremi (São Clemente & Gomes, 1989), a species so far grouped among the species lacking visible microtriches on the scolex, has been recently demonstrated, and given the fact that the presence of microscopically visible microtriches on the scolex is variable in some eutetrarhynchid species, a new key to the species of Dollfusiella is provided in which the spinitriches have been given less priority.