Bullhead shark
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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 Template:Convert 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.<ref name=":1">Template:Cite journal</ref>
DescriptionEdit
Bullhead sharks have tapered bodies, with most species reaching around Template:Convert 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.<ref name=":2">Template:Cite book</ref> 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.<ref>Template:Cite journal</ref><ref name=":2" /> The tail fin is also large, with upper and lower lobes separated by a notch.<ref name=":2" /> Bullhead sharks have differentiated teeth, with cusped grasping teeth at the front of the mouth, and flattened teeth at the back of the mouth.<ref name=":1" /> Their egg cases have a spiral colarettes running along their length.<ref>Template:Cite journal</ref>
EcologyEdit
Bullhead sharks live in coastal littoral environments,<ref name=":1" /> generally shallower than Template:Convert, and are usually primarily active at night.<ref name=":2" /> Bullhead sharks ingest prey via suction feeding.<ref>Template:Cite journal</ref> They feed on invertebrate prey, including both hard prey such as crustaceans and sea urchins, and soft bodied prey such as octopuses, as well as predating on fish.<ref>Template:Cite journal</ref> They use their flattened teeth at the back of the mouth to crush hard-shelled prey and fish.<ref name=":1" /> Juveniles generally take softer prey than adults.<ref name=":2" /> The sharp fin spines provide a deterrent to being consumed by predators.<ref name=":2" />
Bullhead shark egg cases are shaped like an auger, with two spiral flanges. This allows the egg cases to become wedged in the crevices of rocky sea floors, where the eggs are protected from predators; however, some bullhead sharks deposit their eggs on sponges or seaweed.<ref>{{#invoke:citation/CS1|citation |CitationClass=web
}}</ref><ref name=":22">Template:Cite journal</ref> Hatchlings are considered large for sharks, reaching over 14 cm in length by the time they leave the egg case.<ref name=":22" /> Bullhead shark eggs typically hatch after 7 to 12 months, depending on the species.<ref name=":22" /> The female Japanese bullhead shark has been known to deposit their eggs in one location along with other females, called a "nest".<ref name=":22" /> The egg case of the Mexican hornshark features a tendril and more rigid flanges, suggesting that egg case design of this species primarily involves anchoring with tendrils rather than wedging into crevices.<ref name=":22" />
SpeciesEdit
Ten living species of bullhead shark have been described:
- 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)
- Heterodontus mexicanus (L. R. Taylor & Castro-Aguirre, 1972) (Mexican hornshark)
- Heterodontus omanensis (Z. H. Baldwin, 2005) (Oman bullhead shark)
- Heterodontus portusjacksoni (F. A. A. Meyer, 1793) (Port Jackson shark)
- Heterodontus quoyi (Fréminville, 1840) (Galapagos bullhead shark)
- Heterodontus ramalheira (J. L. B. Smith, 1949) (whitespotted bullhead shark)
- Heterodontus zebra (J. E. Gray, 1831) (zebra bullhead shark)
- Heterodontus philippi.jpg
A Port Jackson shark, Heterodontus portusjacksoni
- Heterodontus zebra.jpg
Zebra bullhead shark, Heterodontus zebra
See alsoEdit
ReferencesEdit
Further readingEdit
- Compagno, Leonard (2002) Sharks of the World: Bullhead, mackerel and carpet sharks Volume 2, FAO Species Catalogue, Rome. Template:ISBN.
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