No CrossRef data available.
Published online by Cambridge University Press: 14 July 2015
The chimaeroid fishes enter the fossil record in the Triassic, multiply and diversify to at least 16 genera in the later Mesozoic (Stahl, 1999), and then dwindle during the Cenozoic to only six extant genera (Didier, 1995). Their origin and subsequent evolution have been difficult to trace because, like many other chondrichthyans, their remains consist most often of isolated teeth and fin spines freed and scattered after the cartilaginous skeleton disintegrated. Fossil species are commonly based on dental elements—tooth plates that were not shed like shark teeth but worn at the occlusal surface as they grew slowly from the base throughout life. The entire dentition is known from the extant taxa and from the few fossil specimens preserved with the head intact. It consists of a pair of mandibular tooth plates that occludes with two pairs of plates above, a large posterior palatine pair, and a smaller anterior vomerine pair (for dental terminology, see Stahl, 1999).