No definition has been proposed. Lambe (1918:35) coined the taxon Psalisauria as a redundant higher taxon for a new family Psalisauridae, which he erected for the sole genus and species Stegoceras validum (a pachycephalosaur that was known at that time only from cranial fragments). He suggested that both taxa might be placed within Steogsauria, and Hay (1930) later considered Psalisauria synonymous with Stegosauroidea (Stegosauroidae of his usage). Neither taxon ever gained currency, especially after pachycephalosaurian anatomy was better understood in the years that followed. In addition, the familial taxon Psalisdauridae was erected without a type genus.