Introduction p. 5

Material and methods p. 5

Terminology p. 5

Abbreviations p.6

Measurements p. 6

The dentition of H. mexicanus Taylor & Castro-Aguirre, 1972 and H. quoyi (Frémenville, 1840) p. 7

H. mexicanus Taylor & Castro-Aguirre, 1972 p. 7

Dentition of a neonate male H. mexicanus, TL 20 cm p. 7

The symphyseal tooth p. 7

The intermediate tooth p. 8

The medio-lateral tooth p. 8

Dentition of a aged male H. mexicanus, TL 65.7 cm p. 10

The symphyseal tooth p.

The intermediate tooth p. 10

The first medio lateral tooth p. 11

The second medio-lateral tooth p. 12

The postero-lateral tooth p. 12

The posterior tooth p. 14

Heterodontus quoyi (Frémenville, 1840) p. 14

Dentition of a juvenile male H. quoyi, TL 31.0 cm p. 14

The symphyseal tooth p. 14

The intermediate tooth p. 14

The medio-lateral tooth p. 15

The postero-lateral tooth p.

Dentition of an adult male H. quoyi, TL 53.5 cm p. 16

The symphyseal tooth p. 16

The intermediate tooth p. 18

The medio-lateral tooth p. 18

The postero-lateral tooth p. 20

The posterior tooth p. 20

H. quoyi: DNA sequence, dental formulas and  measurements p. 21

Analysis of the dental morphology of H. mexicanus and H. quoyi p. 22

Discussion p. 28

Earlier studies on recent Heterodontus Blainville 1816 p. 28

Remarks on earlier studies p. 29

Conclusions p. 30

Acknowledgements p. 31

References p. 32

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.