Heterodontus

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Classis: Chondrichthyes
Subclassis: Elasmobranchii
Superordo: Selachimorpha
Ordo: Heterodontiformes

Familia: Heterodontidae
Genus: Heterodontus
Species: †H. bonaespei – †H. boussioni – †H. carerens – †H. creamridgensis – †H. duffini – †H. elongatus – †H. falcifer – H. francisci – H. galeatus – †H. granti – †H. halreensis – †H. janefirdae – H. japonicus – †H. laevis – †H. lerichei – †H. lonzeensis – H. mexicanus – †H. moisierensis – H. omanensis – †H. pineti – †H. polonicus – H. portusjacksoni – H. quoyi – H. ramalheira – †H. sarstedtensis – †H. sowasheense – †H. tuberculatus – †H. vincenti – †H. wardenensis – †H. woodwardi – H. zebra – †H. zitteli
Name

Heterodontus Blainville, 1816

Type species: Squalus philippi Bloch & Schneider, 1801
Synonyms

Centracion Gray, 1831
Cestracion Bosc (ex Cuvier), 1816
Gyropleurodus Gill, 1862
Molochophrys Whitley, 1931
Tropidodus Gill, 1863
Wuia (subgenus of Heterodontus) Fowler, 1934
Heterodontus (Wuia) Fowler, 1934

References

Blainville, H. de. 1816. Prodrome d'une nouvelle distribution systématique du règne animal. Bulletin des sciences, par la Société philomathique de Paris 8: 105–112 [sic for 113–120] +121–124. BHL Reference page.

The bullhead sharks are a small order (Heterodontiformes /ˌhɛtəroʊˈdɒntɪfɔːrmiːz/) of modern sharks (Neoselachii). The nine living species are placed in a single genus, Heterodontus, in the family Heterodontidae. 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, well before any of the other Galeomorphii, a group that includes all modern sharks except the dogfish and its relatives. However, they have never been common, and their origin probably lies even further back.

Description

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Bullhead shark egg case

The bullhead sharks are morphologically rather distinctive. The mouth is located entirely anterior to the orbits. Labial cartilages are found in the most anterior part of the mouth. Nasoral grooves are present, connecting the external nares to the mouth. The nasal capsules are trumpet-shaped and well-separated from orbits. Circumnarial skin folds are present, but the rostral process of the neurocranium (braincase) is absent, although a precerebral fossa is present. Finally, the braincase bears a supraorbital crest.

The eyes lack a nictitating membrane. A spiracle is present, but small. The dorsal ends of the fourth and fifth branchial arches are attached, but not fused into a "pickaxe" as in lamniform sharks. Heterodontiforms have two dorsal fins, with fin spines, as well as an anal fin. The dorsal and anal fins also contain basal cartilages, not just fin rays.
Species

Nine 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 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)

References

Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Chondrichthyes entry)". Bulletins of American Paleontology. ocean. 364: 560. Archived from the original on 2012-05-10. Retrieved 2008-01-09.

. N.p.. Web. 10 Jun 2013. http://paleodb.org/cgi-bin/bridge.pl?a=checkTaxonInfo&taxon_no=252518&is_real_user=1