A member of the Catostomus (P.) platyrhynchus species group distinguished by the following characters: distal process of the dentary wide and robust, and proximal process of the dentary shorter than other species in this group; pharyngeal teeth mostly two-pointed, dorsal teeth forked, unlike the mostly single pointed, less bifurcate teeth of C. (P.) platyrhynchus, but similar to C. (P.) jordani and C. (P.) lahontan; hyomandibula narrow, with a large sphenotic condyle and a broader, more robust posterodorsal tip than C. (P.) jordani, but similar to C. (P.) platyrhynchus and C. (P.) lahontan; tall and narrow opercular bone, the width 0.51-0.57 of the over-all height (vs. 0.57-0.61 in other species); combination of post-Weberian vertebrae usually 40-44 (average 1 fewer in other species of the group except jordani); caudal peduncle depth usually 9% of SL (usually 1% higher in other species); and caudal rays pigmented, inter-radial membranes with few or no melanophores (usually immaculate in other species except when introgressed with C. (P.) virescens [in the upper Snake River] and C. (P.) discobolus [in the Green River]. Can be diagnosed from C. (P.) platyrhynchusin the Snake River above Shoshone falls (the geographically closest, potentially genetically connected relative) by having the following characters: 41-58 predorsal scales, means 43-56 (vs. 40-45 predorsal scales, means 42-44); usually 75-85 scales on lateral line, means 77-82 (vs. 80-90 scales, means 83-86); 29-37 gill rakers on the external row of the first arch (vs. 23-31 gill rakers on the external row of the first arch); 35-51 gill rakers on the internal row of the first arch (vs. 33-39 gill rakers on the internal row of the first gill arch) (Ref. 93746).