The subclass Holocephali ("complete heads") is a taxon of cartilaginous fish, of which the order Chimaeriformes is the only surviving group. This group includes the rat fishes (e.g., Chimaera), rabbit fishes (e.g., Hydrolagus) and elephant fishes (Callorhynchus). They preserve today some features of elasmobranch life in Paleaozoic times, though in other respects they are aberrant. They live close to the bottom and feed on molluscs and other invertebrates.