phylogenetic studies, namely the possible placement of the Cyathocotylidae outside the 109 Diplostomoidea (Hernández-Mena et al., 2017), and the Diplostomidae as a basal lineage in the 110 order Plagiorchiida (Brabec et al., 2015). Both results originate from analysis of mtDNA, and we 111 obtained data to determine if these patterns were robust to additional taxon sampling. To decide 112 between what were likely to be conflicting topologies based on mtDNA and rDNA, we 113 employed phylogenomic analyses of ultra-conserved elements (UCEs). 114Although we set out to work on higher relationships among a small number of 115 representative specimens, we were aware that the diversity and identity of diplostomoid species 116 often differs from initial suspicions based on morphology (Blasco-Costa and Locke, 2017). We 117 therefore supported our identifications with morphological comparisons and analysis of 118 additional DNA sequences from closely related species, which led to several findings related to 119 the alpha taxonomy of the seven specimens of principal interest. 120 121 2. Materials and Methods 122 2.1 Specimen collection and identification 123