Bullhead shark
genus of fishes
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. 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.
Description
Bullhead sharks have tapered bodies, with most species reaching around 70–130 centimetres (2.3–4.3 ft) in length. Their bodies vary in colour, including shades of grey, brown, and red and pale colours, and are covered in a variety of patterns, including spots and stripes. They have blunt, proportionally large heads with relatively small mouths and large nostrils, with pronounced ridges above their eyes. They have two dorsal fins, both substantial in size, the first larger than the second, each of which has a rigid fin spine at the front, along with an anal fin.
Begin with the source’s own compact description: “Bullhead shark” is genus of fishes. The dossier treats that line as a proposition to test through Bullhead, shark and genus, not as a finished interpretation.
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The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Aug 4, 2026. The linked authority identifier is Q44511. The Library of Congress control number is sh85060529. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Bullhead shark” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.