Holocephali

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Holocephali Temporal range: 416–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N Devonian–Recent
Chimaera monstrosa, a rat fish
†Helicoprion davisii, a eugeneodontid
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Holocephali Bonaparte, 1832
Orders
Chimaeriformes †Petalodontiformes †Iniopterygiformes †Eugeneodontida †Symmoriiformes?

Holocephali ("complete heads"), sometimes given the name Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes.^[1] The earliest fossils are of teeth and come from the Devonian period. Little is known about these primitive forms, and the only surviving group in the subclass is the order Chimaeriformes.

Chimaeriformes, commonly known as chimaeras, 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. Extinct holocephalans were much more diverse in lifestyles, including shark-like predatory forms and slow, durophagous fish.