Prosanta Chakrabarty, Brant C. Faircloth, Fernando Alda, William B. Ludt, Caleb D. Mcmahan, Thomas J. Near, Alex Dornburg, James S. Albert, Jairo Arroyave, Melanie L. J. Stiassny, Laurie Sorenson, Michael E. Alfaro

Ostariophysi is a superorder of bony fishes including more than 10,300 species in 1,100 genera and 70 families. This superorder is traditionally divided into five major groups (orders): Gonorynchiformes (milkfishes and sandfishes), Cypriniformes (carps and minnows), Characiformes (tetras and their allies), Siluriformes (catfishes), and Gymnotiformes (electric knifefishes). Unambiguous resolution of the relationships among these lineages remains elusive, with previous molecular and morphological analyses failing to produce a consensus phylogeny. In this study, we use over 350 ultraconserved element (UCEs) loci comprising five million base pairs collected across thirty-five representative ostariophysan species to compile one of the most data-rich phylogenies of fishes to date. We use these data to infer higher-level (interordinal) relationships among ostariophysan fishes, focusing on the monophyly of the Characiformes- one the most contentiously debated groups in fish systematics. As with most previous molecular studies, we recover a non-monophyletic Characiformes with the two monophyletic suborders, Citharinoidei and Characoidei, more closely related to other ostariophysan clades than to each other. We also explore incongruence between results from different UCE datasets, issues of orthology, and the use of morphological characters in combination with our molecular data.