Figure 4.

Squaliform and other shark tooth development. All images rendered micro CT data. Scale bars all 10 mm. (a) Virtual cross section through the upper dentition of Scyliorhinus canicula showing the multiple functional tooth rows. (b) Virtual cross section through the lower dentition of Squalus acanthias. (c) Virtual cross section through the lower dentition of Dalatias licha. (d) Lingual view of the replacement teeth in the lower jaw of Dalatias licha. (e) Head of an embryo of Etmopterus spinax; the only mineralized tissues are the tips of the teeth, but the eye lenses are also conspicuous. Northeast Atlantic. (f) Head of a juvenile of Etmopterus spinax; note the incomplete mineralization of the jaws and brachial system and lack of mineralized chondrocranium. Northeast Atlantic. (g) Head of an adult of Etmopterus spinax; note the incomplete mineralization of the chondrocranium in contrast to the strongly mineralized jaws. Northeast Atlantic.