Defining Features[edit | edit source]
Commonly known as Bullhead and Horn Sharks, Heterodontiformes can be identified by the presence of a spine located in front of each dorsal fin. Members of this order also have a blunt head shape and possess an anal fin. Heterodontiformes have differing teeth in both shape and size, thus their name. Typically smaller and sharper teeth are located at the front of their mouth, while larger and flatter teeth are found near the back. They are oviparous. They have 5 gill slits and their nares are connected to their mouths by a deep groove. They do not have a nictitating membrane.
Habitat and Range[edit | edit source]
Heterodontiformes are demersal organisms, living near the bottom of continental shelves at depths of 0 - 275 meters. They are nocturnal and often hide in caves or between rocks during the day. They are found in subtropical and temperate waters in the Pacific Ocean, as well as off the coast of Southern and Western Australia. Some species migrate annually to breeding sites to spawn and lay their eggs.
Fisheries Conservation and Concern[edit | edit source]
The IUCN lists four of the species in this family (Crested Horn Shark, Port Jackson Shark, Zebra Shark, Japanese Bullhead Shark) as "Least Concern." The remaining five species (Horn Shark, Mexican Horn Shark, Oman Bullhead Shark, Galápagos Bullhead Shark, Whitespotted Bullhead Shark) qualify as "Data Deficient." However, most populations can be assumed to be stable; fisheries have little-to-no interest in these sharks, but may catch them on accident as bycatch. Heterodontiformes may be at risk from pollution, climate change, and destructive fishing practices but there are no conservation actions in place as of 2020.
Closest Relatives[edit | edit source]
Orectolobiformes + [Carcharhiniformes + Lamniformes]
Example Species in Heterodontiformes[edit | edit source]
Zebra Bullhead Shark[edit | edit source]
Heterodontus zebra[edit | edit source]
Defining Features: The Zebra Bullhead Shark can reach up to 125 cm in length, with a large, moderately flat head. The dorsal side of its caudal fin is notably longer than the ventral side, and is patterned with the characteristic dark colored vertical bands that are also present along the body. The anal fin is present, as well as two dorsal fins, and two dorsal spines.
Range & Habitat: The Zebra Bullhead Shark is located in the West Pacific, from Japan to Northwestern Australia. It is a marine species found primarily in shallow water and around reefs, from depths of 0 - 200 meters. In the South China Sea this shark is found at depths as deep as 50 m., however around Western Australia it can be found deeper, as far as 200 m.
IUCN Concern: The ICUN Red List classifies this species as "least concern", although it is caught as bycatch in commercial fishing.
Port Jackson Shark[edit | edit source]
Heterodontus portusjacksoni[edit | edit source]
Defining Features: The Port Jackson Shark is most easily identified by the dark pattern said to resemble a harness along the top and sides of its lighter brown body. This species has a small mouth and its nostrils are connected to the mouth through a system of grooves. Teeth are also one of the most defining features of the Port Jackson shark; unlike other sharks, they are different in the front and the back. The front teeth are small and sharp, but the teeth in the back of the mouth are flat and dull so as to better hold, crush, and grind the shells of their prey.
Range & Habitat: The Port Jackson shark can be found in temperate waters surrounding the south coast of Australia. Reports exist of these sharks being discovered off Australia's northern coast and in New Zealand but there is very little evidence that populations of Port Jackson sharks inhabit these areas. The depth at which Port Jackson sharks are located ranges from extremely close to shore to off the continental shelf in waters up to 902 feet deep. Port Jackson sharks take shelter in protective structures like caves from currents during the day. They are known to migrate between refuges for foraging and refuges for reproduction depending on the season.
IUCN Concern: The IUCN Red List lists Port Jackson Sharks as "Least Concern" and has determined that their population trend is stable. The biggest threat posed to this species is being accidentally caught as bycatch by a range of fisheries, sometimes in high numbers.
References[edit | edit source]
Chondrichthyan Tree of Life: sharksrays.org
Florida Museum of Natural History: floridamuseum.ufl.edu
IUCN Redlist: iucnredlist.org
Animal Diversity Web: animaldiversity.org
Fish Base: fishbase.org