Holocephali

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Holocephali Temporal range: Late Devonian–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Chimaera monstrosa, a rat fish
Life restoration of Romerodus, a eugeneodontid
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Holocephali Bonaparte, 1832
Orders
Holocephali sensu lato (Euchondrocephali) †Petalodontiformes †Iniopterygiformes †Eugeneodontida †Symmoriiformes? Holocephali sensu stricto †Cochliodontiformes †Menaspiformes †Chondrenchelyiformes Chimaeriformes

Holocephali ("complete heads"), sometimes given the name Euchondrocephali ("true cartilage heads"), is a subclass of cartilaginous fish in the class Chondrichthyes.^[1] The earliest fossils are of teeth and come from the Devonian period. The only living holocephalans are the chimaeras (Chimaeriformes), though during the late Paleozoic (Carboniferous and Permian) Holocephali was much more diverse, including an array of forms including those considerably different from modern Chimaeriformes, including shark-like predatory forms and slow, durophagous fish.

Chimaeras, also known as rat fish, or ghost sharks, include three living families and a little over 50 species of surviving holocephalans. These fishes move by using sweeping movements of their large pectoral fins. They are deep sea fish with slender tails, living close to the seabed to feed on benthic invertebrates. They lack a stomach, their food moving directly into the intestine.