Abstract of Smith, G.R. 1966. Distribution and evolution of the North American catostomid fishes of the subgenus Pantosteus, genus Catostomus Univ. Mich. Mus. Zool. Misc. Publ 129:1-132.

The mountain suckers are 5 species of small fishes related the genus Catostomus, specific to the Columbia (columbianus, upper Colorado discobolus, lower Colorado (clarki), Great Basin-Missouri and north into Canada (platyrhynchus), Rio Grande and south into Mexico (plebeius), and Santa Ana (santa-anae) drainages. The species inhabit moderate- gradient streams and are distinguished by their lip structure, vertebral numbers, scale numbers, fin ray numbers, gut length, and pigment patterns. All species hybridize with sympatric related Catostomus.