Full reference: R. Estes and J. A. Tihen. 1964. Lower vertebrates from the Valentine Formation of Nebraska. American Midland Naturalist 72(2):453-472
Type specimen: U.N.S.M. No.61019, a partial skull (right frontoparietal). Its type locality is Norden Bridge Quarry, which is in a Barstovian channel sandstone in the Valentine Formation of Nebraska.