Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish (not to be confused with the rattails), or rabbitfishes (not to be confused with the "true" rabbitfishes of the family Siganidae). They may be the "oldest and most enigmatic groups of fishes alive today." At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks, though in evolutionary terms they branched off from sharks...
