Asian Diver – March 2018

Sharkopedia

Most of us are probably only aware of a fraction of the over 470 known
species of sharks. Having been around for hundreds of millions of
years, they have evolved into incredibly diverse forms, from the ray-like
angelshark and the intriguing great hammerhead, to the tiny dwarf
lanternshark and the formidable whale shark.
The best way to appreciate their diversity is by understanding their
scientific classification as expressed through the seven main taxonomic
ranks: kingdom, phylum, class, order, family, genus, and species. As part
of the kingdom Animalia, sharks belong to the phylum Chordata and the
subclass Elasmobranchii, under which rays, skates, and sawfish are also
organised. The elasmobranchs include eight extant orders of shark, each
of which is determined by certain unique biological characteristics.

CARCHARHINIFORMES

With over 270 species, the ground sharks are

the largest order of sharks and include many

commonly encountered species by divers,

such as blue, tiger, bull, and hammerhead

sharks. They are known for their adaptability

to a variety of climates and conditions, and

can be found in all parts of the world.

Characteristics: anal fin, five gill slits, two

dorsal fins, no fin spines, mouth behind the

eyes, nictitating eyelids

HETERODONTIFORMES

This order consists of only one family,

Heterodontidae, commonly referred to

as bullhead or horn sharks. There are

nine species in the order, with the largest

reaching just 1.65 metres long.

Characteristics: pig-like snout, anal fin,

five gill slits, two dorsal fins, dorsal fin

spines, no nictating eyelids

PRISTIOPHORIFORMES
Pristiophoriformes, or sawsharks, are
characterised by their saw-like snout.
There are a total of eight species of
sawsharks, which occur over sand or
mud and use their snout to find and
slash their prey.

Characteristics: long snout, five or
six gill slits, two dorsal fins, mouth
underneath, no anal fin, wide pectoral fins

SQUALIFORMES

This order of dogfish sharks

includes around 119 species in

seven families. They range

from the smallest shark of all, the

dwarf lanternfish, to one of the largest

known sharks, the Greenland shark.

Characteristics: two dorsal fins, five gill

slits, short snout, mouth underneath, no

anal fin, no nictitating eyelids