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
or Bullhead Sharks
Lamniformes: Mackerel Sharks
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.
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.
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.
are distinctive with a long snout edged with sharp, straight teeth. 1