This study investigates the systematics of Paracreptotrema Choudhury, Pérez-Ponce de León, Brooks and Daverdin, 2006 using morphological data (stained whole mounts and scanning electron microscopy) and partial sequences of the 28S ribosomal rRNA gene, obtained from freshly collected material. In total, 484 specimens representing 4 species, i.e., Paracreptotrema blancoi (157), Paracreptotrema profundulusi (12), Paracreptotrema rosenthali (8), and Paracreptotrema blancoi sensu Salgado-Maldonado et al. (2011) (307) were collected. Existing museum depositions were also studied. The 28S rRNA gene sequences of these Paracreptotrema spp. were aligned, along with sequences from 22 other allocreadiids and 4 other non-allocreadiid xiphidiatan species. Bayesian inference and maximum likelihood analyses indicated a paraphyletic Paracreptotrema split into 3 clades: 1 comprising P. blancoi and P. rosenthali that was sister to a clade formed by 3 other species of allocreadiids (species of Wallinia, Creptotrematina, and Auriculostoma) typically found in characid fishes, a second clade formed solely by Paracreptotrema heterandriae as the sister taxon of the aforementioned species, and a third by P. profundulusi and specimens erroneously identified as P. blancoi. Two new taxa were erected to reflect these results: Paracreptotrematoides for Paracreptotrema heterandriae, and Pseudoparacreptotrema for Paracreptotrema profundulusi and P. macroacetabulata (the species erroneously identified as P. blancoi from profundulids across Middle America). Closer consideration of the morphology corroborates these findings. The revised systematics also indicated that Paracreptotrema spp. are found in poeciliids, whereas Pseudoparacreptotrema spp. parasitize profundulids. The study demonstrates the value of an integrative taxonomy approach to address the apparently complicated systematics of the allocreadiids.

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