Chimaeridae is a family of fishes in the order Chimaeriformes. The body is valvate, tapering to the tail. The skin is bare. The first dorsal fin is short, high with a strong spike, the second - low, very long. The caudal fin is heterocercal or in the form of a long thread. There are copulatory organs - pterygopodia. Includes 6 genera, about 30 species. Size from 60 cm to 2 m. Marine, mainly benthic fish, living at depths from a few metres to 2500 m. Found in warm and temperate waters of all oceans. Slow-moving. Lay 1-2 eggs in horn capsules. Feeds on molluscs, echinoderms, crustaceans and fish.

They resemble other members of the genus, but have a short, rounded snout. Some species have a long, rounded tail, which is why this family is called "sea rats" in English. Members of this family carry poisonous barbs on their backs that can injure humans.

Characterised by an elongated body (unlike rays) and a mouth at the end of the snout (unlike other Selachii). The pectoral fins are not attached to the head (as in stingrays). The anterior dorsal fin has a strong spine and the posterior dorsal fin sometimes extends to a considerable length. The tail ends in a long whip-like appendage. 

R. Chimaera is a chimaera, sea cat or sea rat with a keeled snout. The posterior dorsal fin extends far back and almost merges with the caudal fin. 

Ch. monstrosa - found off the coasts of Europe (northern seas, Mediterranean), as well as off the southern tip of Africa and the coast of Japan. Males have a thin bony projection between the eyes that curves forward. The skin is smooth and shines in a variety of colours. Reaches 1 - 1.5 metres in length. Feeds on crabs, barnacles and small fish. The eggs are covered with a horny shell. The meat is not eaten, but the eggs are considered a delicacy. In Norway, the liver of the chimaera is used for medicinal purposes. 

Another species, Ch. affinis, is found off the coast of Portugal, and Ch. collici off the west coast of North America. R. callorhynchus - snout with a fleshy blade at the end. Posterior dorsal fin high and short.

C. antarcticus - In the Antarctic Ocean. The eggs have a dense leaf-like shell, which some see as an imitation of fucus leaves.