Taxonomy: Superclass Gnathostomata - jawed fishes
Class Chondrichthyes - cartilaginous fishes
Heterodontiformes
Order Heterodontiformes – horn (bullhead) shark
Family Heterodontidae
1 genus (Heterodontus), ~ 9 species
Description: Ancient lineage, snout pig-like with deep nasoral groove that connect nostrils to mouth, labial cartilage in anterior of mouth, prominent brow ridge, eyes without nictitating fold, five pairs of gill slits, only living sharks with dorsal fin spines and anal fin, molar-like crushing teeth in the rear jaw in adults, medium body size (1.5 meters), oviparous- lay eggs also referred to as ‘mermaids purse’
Habitat: Mostly rocky and kelp forest habitat in shallow (<100 meters deep) coastal marine waters
Distribution: Warm temperate and tropical parts of western and eastern Pacific and western Indian oceans
Ecology and life history: Short migration distance (30 m) during the winter; segregate based on age group: adolescent sharks remain in deeper water (40 - 150m), adults migrate to shallow water; segregation limits competition for food and habitat: juveniles live in sandy bottoms with little vertical relief, while adults reside on rocky reefs of caves/crevices, or regions of algae (kelp, cyanobacteria, diatoms, dinoflagellates); nocturnally active predators, juveniles eat buried worms, adults small fishes/crustacean/molluscs, grind up food and then swallow it, regurgitating hard parts later; little known about age and growth of species; estimates average longevity 25 years; oviparous with females laying two eggs every two weeks (24 eggs over breeding period)
Additional details: No commercial value, generally captured accidentally as bycatch, used for sporting purposes and jewelry manufacturing, fossil evidence from early
Jurassic period (206-144 MYA), three of the bullhead species are endangered
(Heterodontus galeatus, Heterodontus portusjacksoni, Heterodontus zebra)
Recent Research: the most recently found bullhead species was Heterodontus
omanensis (Baldwin, 2005)
References used:
Baldwin, Z. H. 2005. A New Species of Bullhead Shark, Genus Heterodontus (Heterodontiformes: Heterodontidae), from Oman. American Society of Ichthyologists and Herpetologists. Copeia. 262-4.
Bond, C. E. 1996. Biology of Fishes, 2 nd . ed. Saunders College Publishing, Fort Worth
Carlisle, A.B. 2006. Heterodontus francisci. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4.
< www.iucnredlist.org
>. 03 February 2011.
Paxton, J. R. and W. N. Eschmeyer. 1998. Encyclopedia of fishes 2nd ed. Academic Press.