Chimaera information and info on the Chimaeriformes also known as Chimaeras
Chimaeras are cartilaginous fish in the order Chimaeriformes, known as :
- ghost sharks
They may be the "oldest and most enigmatic groups of fishes alive today."
The chimeara's closest living relatives are sharks, though in evolutionary terms they branched off from sharks nearly 400 million years ago and have remained isolated ever since.
Today they are largely confined to deep water.
Chimaeras live in temperate water on ocean floors down to 2600 metres (8500 ft) depth, with few occurring at depths shallower than 200 metres (660 ft). Exceptions include the members of the genus Callorhinchus, the rabbit fish and the spotted ratfish, which can be found at relatively shallow depths.
Consequently, these are also among the only species from the Chimaera order that are kept in public aquariums.
They have elongated, soft bodies, with a bulky head and a single gill-opening. They grow up to 1.5 metres (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, chimaeras have a skeleton 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 venomous spine located in front of the dorsal fin.
Chimaeras resemble sharks in some ways: they employ claspers for internal fertilization of females and they lay eggs with leathery cases. However, unlike sharks, male chimaeras also have retractable sexual appendages on the forehead (a type of tentacle) and in front of the pelvic fins. The females lay eggs in spindle-shaped leathery cases.
They also differ from sharks in that their upper jaws are fused with their skulls and they have separate anal and urogenital openings. They also lack the sharks many sharp and replaceable teeth, having instead just three pairs of large permanent grinding tooth plates.
They have gill covers like bony fishes.