Chimaeras are

cartilaginous fish Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue ...

in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with

rattail Grenadiers or rattails are generally large, brown to black gadiform marine fish of the subfamily Macrourinae, the largest subfamily of the family Macrouridae. Found at great depths from the Arctic to Antarctic, members of this subfamily are am ...

Opisthoproctidae Barreleyes, also known as spook fish (a name also applied to several species of chimaera), are small deep-sea argentiniform fish comprising the family Opisthoproctidae found in tropical-to-temperate waters of the Atlantic, Pacific, and Indian ...

, or

Siganidae Rabbitfishes or spinefoots are perciform fishes in the family Siganidae. The 29 species are in a single genus, ''Siganus''. In some now obsolete classifications, the species having prominent face stripes—colloquially called foxfaces– ...

, respectively. At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks and

ray Ray may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), a bony or horny spine on a fin Science and mathematics * Ray (geometry), half of a line proceeding from an initial point * Ray (g ...

s, though their last common ancestor with them lived nearly 400 million years ago. Today, they are largely confined to deep water.

Description and habits

Chimaeras live in temperate ocean floors down to deep, with few occurring at depths shallower than . Exceptions include the members of the genus ''

Callorhinchus ''Callorhinchus'', the plough-nosed chimaeras or elephantfish, are the only living genus in the family Callorhinchidae (sometimes spelled Callorhynchidae). A few extinct genera only known from fossil remains are recognized. ''Callorhinchus'' spp ...

'', the

rabbit fish ''Chimaera monstrosa'', also known as the rabbit fish or rat fish, is a northeast Atlantic Ocean, Atlantic and Mediterranean Sea, Mediterranean species of cartilaginous fish in the family Chimaeridae. The rabbit fish is known for its characteris ...

and the

spotted ratfish The spotted ratfish (''Hydrolagus colliei'') is a chimaera found in the north-eastern Pacific Ocean. Often seen by divers at night in the Pacific Northwest, this cartilaginous fish gets its characteristic name from a pointed rat-like tail. The r ...

, which locally or periodically can be found at shallower depths. Consequently, these are also among the few species from the chimaera order kept in public aquaria. They live in all the oceans except for the Arctic and Antarctic oceans. They have elongated, soft bodies, with a bulky head and a single gill-opening. They grow up to 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 composed of

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

. Their skin is smooth and naked, lacking placoid scales (except in the claspers), and their color can range from black to brownish gray. For defense, most chimaeras have a venomous

spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolog ...

in front of the dorsal fin. They use these fins to "fly" through water. The usual diet of chimaeras consist of crustaceans, and more specifically, they include ophiurans and molluscs. Chimaeras resemble sharks in some ways: they employ claspers for internal fertilization of females and they lay eggs with 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

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