Bullhead shark

Bullhead shark Temporal range: Late Jurassic–Present PreꞒ Ꞓ O S D C P T J K Pg N
Horn shark, Heterodontus francisci
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Clade:	Neoselachii
Subdivision:	Selachimorpha
Superorder:	Galeomorphii
Order:	Heterodontiformes
Family:	Heterodontidae J. E. Gray, 1851
Genus:	Heterodontus Blainville, 1816
Type species
Squalus portusjacksoni F. A. A. Meyer , 1793
Species
See text

The bullhead sharks are members of the genus Heterodontus, the only members of the family Heterodontidae and only living members of the order Heterodontiformes. All are relatively small, with the largest species reaching just 1.65 metres (5.5 ft) in maximum length. They are bottom feeders in tropical and subtropical waters.

The Heterodontiforms appear in the fossil record in the Early Jurassic.^[1] The oldest fossils of the modern genus date to the Late Jurassic. Despite the very ancient origins of this genus and its abundance in the fossil record, phylogenetic evidence indicates that all extant species in the genus arose from a single common ancestor that survived the Cretaceous-Paleogene extinction, with diversification into modern species only starting around the mid-Eocene.^[2]

Description

The bullhead sharks are characterised by a broad head, heavy brow, stubby snout and small mouth. The mouth is located entirely

• Heterodontus francisci (Girard, 1855) (horn shark)
• Heterodontus galeatus (Günther, 1870) (crested bullhead shark)
• Heterodontus japonicus (Maclay & W. J. Macleay, 1884) (Japanese bullhead shark)
• Heterodontus marshallae White, Mollen, O'Neill, Yang & Naylor, 2023 (painted hornshark)
• Castro-Aguirre
  , 1972) (Mexican hornshark)
• Heterodontus omanensis (Z. H. Baldwin, 2005) (Oman bullhead shark)
• Heterodontus portusjacksoni (F. A. A. Meyer, 1793) (Port Jackson shark)
• Fréminville
  , 1840) (Galapagos bullhead shark)
• J. L. B. Smith
  , 1949) (whitespotted bullhead shark)
• Heterodontus zebra (J. E. Gray, 1831) (zebra bullhead shark)