The dentitions of the extant species Heterodontus mexicanus Taylor & Castro-Aguirre, 1972 and Heterodontus quoyi (Frémenville, 1840) (Elasmobranchii, Chondrichthyes) is studied, clarifying all intraspecific and interspecific characteristics for these two species, thus forming a base in the understanding of francisci–type dentitions. Dignathic heterodonty was observed in H. mexicanus. Keywords: Selachii, Heterodontidae, Heterodontiformes, basal ornamentation.weiterlesen