Shark Species and Taxonomic Information
This Knowledge Base, provided by Marine Themes, is not intended to be an authority on taxonomic order. The following information was correct at time of publication but, no doubt, has since changed and will change yet again. It is intended to provide a basic knowledge of some of the more "obvious", though not necessarily common, animal species found in our database.
Fish species can be divided into three distinct groups: Osteichthyes (fishes with a bony skeleton), Chondrichthyes (fish with cartilage skeleton) and Agnatha (jawless fish i.e. Hagfish). Sharks, Rays and Chimaeras are Chondrichthyans, all having a skeleton made of cartilage, a substance similar in structure to your ears or nose. The Chondrichthyans are further broken up into two groups: Elasmobranchs (sharks and rays) and Holocephali (chimaeras or ghost sharks and spookfish). Elasmobranchs are then divided into two groups: Selachii (sharks) and Batoidea (rays).
Sharks and rays are primarily differentiated by their gill slits. Sharks always have their gills originating on the sides of the head (even if they do terminate, at times, under the head) while rays always have their gill slits under the head. Rays are mostly flattened in profile and may have spines on the tail. Some ray species are similar to sharks, with rounded bodies and shark-like dorsal fins and tail, and some sharks are ray-like with flattened bodies. However, the gill placement is always a determining feature.
There are eight distinct orders of sharks:
Hexanchiformes:
Frilled, Sixgill & Sevengill Sharks
Squaliformes: Dogfish or
Dogsharks
Heterodontiformes: Hornsharks
or Bullhead Sharks
Orectolobiformes: Carpetsharks
Lamniformes: Mackerel Sharks
Carcharhiniformes: Groundsharks
Squatinaformes: Angelsharks
Pristiophoriformes: Sawsharks
Some may argue that there are at least ten, splitting the Hexanchiformes and putting the Frilled Shark into Chlamydoselachiformes and taking the Bramble Sharks out of the Squaliformes order and creating the Echinorhiniformes family.
The distinctive features of each group are, in part:
Hexanchiformes: All have 6 or 7 gills (all other species
have 5). Single spineless dorsal and anal fins. 2 families.
Squaliformes: No anal fin.
Two dorsal fins (often with spines). 7 families.
Heterodontiformes: Anal
fin present, both dorsal fins have spines. 1 family.
Orectolobiformes: Anal fin,
two spineless dorsal fins. Barbels on nostrils. 7 families.
Lamniformes: Anal fin, two
spineless dorsal fins, mouths reach back behind eyes, no nictitating eyelid.
7 families.
Carcharhiniformes: Anal
fin, two spineless dorsal fins, mouths reach back behind eyes, nictitating
eyelid. 8 families.
Squatinaformes: No anal
fin, two dorsal fins without spines set well back near the tail. Flattened
ray-like body. 1 family.
Pristiophoriformes: Sawsharks
are distinctive with a long snout edged with sharp, straight teeth. 1
family.
