Phylogenetic analyses based on molecular and morphological data reveal a new species of Abildgaard, 1790 (Digenea: Strigeidae) and taxonomic changes in strigeids infecting Neotropical birds of prey.

Members of the genus Abildgaard, 1790 are endoparasites of birds distributed worldwide. Adults of an undescribed species of the genus were collected from the intestines of two hawk species ( and ). Other species identified as that were described in Argentina were also recovered from two hawk species ( and ) in three localities along the coasts of Mexico. Specimens of the two species were sequenced for three molecular markers, the internal transcribed spacers locus (ITS1-5.8S rDNA- ITS2) and the domains D1-D3 from the large subunit from nuclear ribosomal DNA and the cytochrome oxidase subunit 1 from mitochondrial DNA. The newly sequenced specimens were aligned with other strigeids sequences downloaded from GenBank. Maximum likelihood and Bayesian analyses inferred with each molecular marker revealed that our specimens of sp. formed an independent lineage, which is recognized herein as a new species, n. sp., representing the first species in Mexico and the 16th in the Neotropical region. Morphologically, the new species is distinguished from other congeneric species from the Americas by having an oral sucker with several papillae around it, well-developed pseudosuckers (118-248 μm), a tegument covered with tiny spines, a larger cone genital (193-361 × 296-637) and a larger copulatory bursa (247-531 × 468-784). Our phylogenetic analyses revealed that is not closely related to other members of the genus and is nested within , suggesting that should be transferred to to form n. comb., expanding its distribution range from Mexico to Argentina. Finally, the analyses also revealed that the taxonomy and systematics of should be re-evaluated, combining morphological and molecular characteristics.