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Shark Species and Taxonomic Information

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

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). 3 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.



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