Set of teeth from 3 species in 3 genera of the family Hexanchidae

This is a set of teeth from three species belonging to the Hexanchidae family.

① Bluntnose sixgill shark (Hexanchus griseus) - Left mandibular third tooth (collected from the jaw of a male approximately 310 cm in total length) / Tooth width: 28mm
② Sharpnose sevengill shark (Heptranchias perlo) - Left mandibular third tooth (collected from the jaw of a male approximately 117 cm in total length) / Tooth width: 16mm
③ Broadnose sevengill shark (Notorynchus cepedianus) - Left mandibular second tooth (collected from the jaw of a male approximately 200 cm in total length) / Tooth width: 18mm

The broadnose sevengill shark is designated as endangered, while the bluntnose sixgill shark and sharpnose sevengill shark are listed as near threatened. Each of these species is rare. The broadnose sevengill shark, in particular, is extremely difficult to obtain. All three species have very thin teeth in the labiolingual direction, making it exceptionally challenging to assemble a set of all three for comparison.
Bluntnose sixgill sharks are known as deep-sea scavengers and possess green eyes called tapeta lucida, which are organs that gather scarce light in the deep ocean. While their fossils have been discovered, bluntnose sixgill sharks are rare. Sharpnose sevengill sharks are even more difficult to collect, and broadnose sevengill sharks have rarely been collected in Japan.