Description and habits
Chimaeras live in temperate ocean floors down to 2,600 m (8,500 ft) deep, with few occurring at depths shallower than 200 m (660 ft). Exceptions include the members of the
rabbit fish and the
spotted ratfish, which locally or periodically can be found at relatively shallow depths. Consequently, these are also among the few species from the Chimaera order kept in
 They have elongated, soft bodies, with a bulky head and a single
gill-opening. They grow up to 150 cm (4.9 ft) in length, although this includes the lengthy tail found in some species. In many species, the snout is modified into an elongated sensory organ.
Like other members of the class
Chondrichthyes, chimaera skeletons are constructed of
cartilage. Their skin is smooth and largely covered by
placoid scales, and their color can range from black to brownish gray. For defense, most chimaeras have a
spine in front of the
Chimaeras resemble sharks in some ways: they employ
claspers for internal fertilization of females and they lay
leathery cases. They also use
electroreception to find their prey.
 However, unlike sharks, male chimaeras also have retractable
sexual appendages on the forehead (a type of
 and in front of the
 The females lay eggs in
They also differ from sharks in that their upper jaws are fused with their skulls and they have separate
urogenital openings. They lack sharks' many sharp and replaceable teeth, having instead just three pairs of large permanent grinding tooth plates. They also have gill covers or
opercula like bony fishes.