Revised classification and phylogenetic hypothesis for the Acanthostominae Looss, 1899 (Digena: Opisthorchiformes: Cryptogonimidae)

Specimens of an acanthostome digenean originally identified as Acanthostomum scyphocephalum and later transferred to Timoniella are described and named as a distinct species of Timoniella. Acanthostomum scyphocephalum sensu strictu is included in an updated phylogenetic analysis of the acanthostome digeneans. Acanthostomum is paraphyletic if Atrophecaecum is excluded from it; accordingly, the two genera are synonymized. The resulting annotated phylogenetic classification, with synapomorphic diagnoses, includes Acanthostomum as the sister-group of Caimanicola, Proctocaecum as their sister-group, the monotypic Gymnatrema as their sister-group, and Timoniella as the basal sister-group. Four new subgenera are proposed, one in Timoniella, one in Proctocaecum, and two in Acanthostomum.