Comments on the Gonotyl of Proctocaecum macroclemidis (Tkach and Snyder, 2003) n. comb. (Digenea: Acanthostomidae: Acanthostominae), with a Key to the Genera of Acanthostominae and New Phylogenetic Tree for Proctocaecum Baugh, 1957
Date of this Version
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.