Notorynchus primigenius allegedly differs from the modern N. cepedianus (PERON, 1807) by having more erect cusps. However variations in the modern tooth form (and the fossils as illustrated) makes this a somewhat dubious distinction. Thus, it is believed that the fossil species is the same as the modern one. A potential source of confusion occurs in that the fossil species naming predates the modern species. The posterior teeth are minute, irregular, and stubby and would be barely recognizable as a tooth. In addition to being smaller, these teeth differ from Hexanchus in having less cusps on the lower teeth (7 vs 8 - 12+) and larger more recurved serrations on the anterior side of the tooth which don't extend as far down along the front of the root.