Comments on the Gonotyl of \u3ci\u3eProctocaecum macroclemidis\u3c/i\u3e (Tkach and Snyder, 2003) n. comb. (Digenea: Acanthostomidae: Acanthostominae), with a Key to the Genera of Acanthostominae and New Phylogenetic Tree for \u3ci\u3eProctocaecum\u3c/i\u3e Baugh, 1957

The species recently described as Acanthostomum macroclemidis possesses the gonotyl in the form of a solid muscular pad uniquely diagnostic for species of Proctocaecum and is accordingly transferred to that genus. An artificial key to the 5 acanthostomine genera, as well as an updated phylogenetic hypothesis for the 10 known species of Proctocaecum, based on 11 characters and including 2 species described since the last phylogenetic analysis, are presented. The single most parsimonious phylogenetic tree with a consistency index of 87.5% suggests that Proctocaecum originated in Africa and spread to North America and South America before the breakup of Pangaea. As a result, the 2 North American and 1 South American species are most closely related to different African members of the genus. African and Indo-Pacific species inhabit crocodylids; hence, the occurrence of North American species in alligatorids and chelonians and a South American species in alligatorids are the result of host switches