is the only living member of the Dermochelyidae
family, sister taxon to the family Cheloniidae
, which contains all other extant sea turtles (6 species in 5 genera).Dermochelyidae
is distinguished by the lack of a hard, rigid carapace (shell) comprised of keratinous scutes - a feature that all other sea turtles share. Instead it has a carapace formed of flexible tissue, overlain by a matrix of small (1–2cm) bones called osteoderms and covered in a layer of skin.It possesses 7 lateral ridges running the length of the carapace, although other extinct Dermochelyidae
species have been characterised by the possession of different numbers of such ridges.Its skeleton has a high cartilage ratio making it highly flexible and it has particularly long front flippers.