Hexanchiformes
Frill sharks, cow sharks
Taxonomy:
Superclass Gnathostomata – jawed fishes
Class Chondrichthyes – cartilaginous fishes
Subclass Elasmobranchii
Order Hexanchiformes
Families Chlamydoselachidae (frill shark) & Hexanchidae (cow sharks)
4 genera, 5 species
VT species: none - order is all marine species
Description: primitive, jawed, cartilaginous, without spine, fusiform (Hexanchidae) or
saggitaform (Chlamydoselachidae), single posterior spineless dorsal fin, anal fin present, six or
seven gill slits, nictitating fold absent. Frill shark (Chlamydoselachus anguineus) possessing
loose skin extending from the interbrachial septa (family Chlamydoselachidae). Length ranging
from a maximum of 2 m for the frill shark and up to a maximum of 4.7 (possibly 8) m in the
[bluntnnose] sixgill shark (Hexanchus griseus).
Habitat: Marine, inhabiting continental shelf and slope waters, except the sevengill shark
[Notorynchus cepedianus] which inhabits shallow coastal waters.
Distribution: Present in cold waters and warmer coastal waters (sevengill shark) from tropical
through temperate and boreal zones of the Pacific, Indian and Atlantic Oceans.
Ecology and life history: Ovoviviparous, though little else is known about many species in this
order given the difficulty of study in waters of the continental shelf and slope. At least two
species give birth in shallow waters. Mouth terminal (Chlamydoselachidae) or subterminal
(Hexanchidae), feeding on herring and similar small fishes; teeth with three cusps
(Chlamydoselachidae) or heterodont (Hexanchidae).
Additional details: Type of tricuspid teeth in the frill shark similar to those present in extinct
“cladodont” sharks, suggesting this species may be an evolutionary link between primitive and
modern sharks. The sixgill shark has been used in the production of oil and meal.
References used:
Bond, C.E. 1996. Biology of Fishes, 2nd. Ed. Saunders College Publishing, Fort Worth.
Martin, R. A. Carcharhiniformes: Ground or Whaler Sharks. ReefQuest Centre for Shark
Research. Accessed 25 Jan 2009.
<http://www.elasmo-research.org/education/shark_profiles/carcharhiniformes.htm>
Martin, R. A. hexanchiformes: Cow Sharks. ReefQuest Centre for Shark Research. Accessed
25 Jan 2009.
<http://www.elasmo-research.org/education/shark_profiles/hexanchiformes.htm>
Nelson, J.S. 1994. Fishes of the World, 3rd. ed. John Wiley & Sons, Inc. New York.