14
3. Squaliformes (Dogfi sh) have been around since the Jurassic period (160–200
mya). This is a large and varied order containing 106 identifi ed species in seven
families; bramble sharks ( Echinorhinidae ), dogfi sh sharks ( Squalidae ), gulper
sharks ( Centrophoridae ), lantern sharks, ( Etmopteridae ), sleeper sharks
( Somniosidae ), roughsharks ( Oxynotidae ), and kitefi n sharks ( Dalatiidae ). The
dogfi sh sharks’ habitat is wide ranging, with species found in marine estuarine
environments world-wide. Currently they are the only known sharks to be found
at high latitudes close to the poles. Their greatest diversity occurs in deepwater.
They have a cylindrical/torpedo shaped body with the eyes on the side of the
head, 5 gill slits, 2 dorsal fi ns (in some species these are spined), and no anal fi ns.
They are ovoviviparous, with some species having a low fertility of just 1 pup per
litter (e.g.: the gulper shark Centrophorus granulosus ) and other species having
a very long gestation period of 18–24 months (e.g.: the spiny dogfi sh Squalus
acanthias ). Some species are thought to be solitary; others form schools that
range long distances during seasonal and annual migrations.
4. Hexanchiformes (Frilled and Cow sharks) are considered to be amongst the most
“ancient” forms of living sharks dating back to the Permian period (260–300
mya). They are comprised of 2 families; cow sharks (Hexanchidae of which
there are 2 species) and frilled sharks (Chlamydoselachidae of which there are 4
species). The frilled sharks are eel-like with distinctive spaced out teeth, the cow
sharks are the more conventional cylindrical shape. Both families have 6 or seven
gill slits, 1 dorsal fi n, and anal fi ns are present. Most of the species are found
worldwide, predominantly in the deep cold water of the tropics. They are
ovoviviparous with frilled sharks producing 6–12 pups per litter and cow sharks
ranging from 6 to 108 pups depending on the species.
5. Carcharhiniformes (Ground Sharks) are the largest, most diverse and widespread
order of sharks. Dating from the Jurassic period (160–200 mya) the ground
sharks are comprised of around 247 species in 8 families; catsharks ( Scyliorhinidae ),
fi nback catsharks ( Proscylliidae ), false catsharks ( Pseudotriakidae ), barbeled
houndsharks ( Leptochariidae ), houndsharks ( Triakidae ), weasel sharks
( Hemigaleidae ), requiem sharks ( Carcharhinidae ), and hammerhead sharks
( Sphyrnidae ).
These shark species inhabit cold to tropical seas, intertidal to deep water and
pelagic Open Ocean. Their physical appearances can be quite different; from the
Daggernose shark ( Isogomphodon oxyrhynchus ) to the Great Hammerhead
( Sphyrna mokarran ), however all have 5 gill slits, 2 dorsal fi ns (with one exception; the aptly named “Onefi n catshark” Pentanchus profundicolus ) and anal fi ns.
Reproductive strategies are also quite varied. Both the catsharks and the fi nback catsharks are oviparous (egg laying) and ovoviviparous with typically 1–2
eggs or live pups per litter, false catsharks are ovoviviparous (2–4 pups per litter),
oophagous (meaning “egg eating”, pups feed off eggs produced by the ovary
whilst inside the uterus, 2 pups per litter), viviparous (pups nurtured via a placental
connection, 7 pups per litter). The barbeled houndsharks reproductive method is
unknown. Houndsharks are ovoviviparous (2–52 pups per litter) and viviparous
(2–20 pups per litter), the exact method in weasel sharks is unknown but they do
1 Introduction
3. Squaliformes (Dogfi sh) have been around since the Jurassic period (160–200
mya). This is a large and varied order containing 106 identifi ed species in seven
families; bramble sharks ( Echinorhinidae ), dogfi sh sharks ( Squalidae ), gulper
sharks ( Centrophoridae ), lantern sharks, ( Etmopteridae ), sleeper sharks
( Somniosidae ), roughsharks ( Oxynotidae ), and kitefi n sharks ( Dalatiidae ). The
dogfi sh sharks’ habitat is wide ranging, with species found in marine estuarine
environments world-wide. Currently they are the only known sharks to be found
at high latitudes close to the poles. Their greatest diversity occurs in deepwater.
They have a cylindrical/torpedo shaped body with the eyes on the side of the
head, 5 gill slits, 2 dorsal fi ns (in some species these are spined), and no anal fi ns.
They are ovoviviparous, with some species having a low fertility of just 1 pup per
litter (e.g.: the gulper shark Centrophorus granulosus ) and other species having
a very long gestation period of 18–24 months (e.g.: the spiny dogfi sh Squalus
acanthias ). Some species are thought to be solitary; others form schools that
range long distances during seasonal and annual migrations.
4. Hexanchiformes (Frilled and Cow sharks) are considered to be amongst the most
“ancient” forms of living sharks dating back to the Permian period (260–300
mya). They are comprised of 2 families; cow sharks (Hexanchidae of which
there are 2 species) and frilled sharks (Chlamydoselachidae of which there are 4
species). The frilled sharks are eel-like with distinctive spaced out teeth, the cow
sharks are the more conventional cylindrical shape. Both families have 6 or seven
gill slits, 1 dorsal fi n, and anal fi ns are present. Most of the species are found
worldwide, predominantly in the deep cold water of the tropics. They are
ovoviviparous with frilled sharks producing 6–12 pups per litter and cow sharks
ranging from 6 to 108 pups depending on the species.
5. Carcharhiniformes (Ground Sharks) are the largest, most diverse and widespread
order of sharks. Dating from the Jurassic period (160–200 mya) the ground
sharks are comprised of around 247 species in 8 families; catsharks ( Scyliorhinidae ),
fi nback catsharks ( Proscylliidae ), false catsharks ( Pseudotriakidae ), barbeled
houndsharks ( Leptochariidae ), houndsharks ( Triakidae ), weasel sharks
( Hemigaleidae ), requiem sharks ( Carcharhinidae ), and hammerhead sharks
( Sphyrnidae ).
These shark species inhabit cold to tropical seas, intertidal to deep water and
pelagic Open Ocean. Their physical appearances can be quite different; from the
Daggernose shark ( Isogomphodon oxyrhynchus ) to the Great Hammerhead
( Sphyrna mokarran ), however all have 5 gill slits, 2 dorsal fi ns (with one exception; the aptly named “Onefi n catshark” Pentanchus profundicolus ) and anal fi ns.
Reproductive strategies are also quite varied. Both the catsharks and the fi nback catsharks are oviparous (egg laying) and ovoviviparous with typically 1–2
eggs or live pups per litter, false catsharks are ovoviviparous (2–4 pups per litter),
oophagous (meaning “egg eating”, pups feed off eggs produced by the ovary
whilst inside the uterus, 2 pups per litter), viviparous (pups nurtured via a placental
connection, 7 pups per litter). The barbeled houndsharks reproductive method is
unknown. Houndsharks are ovoviviparous (2–52 pups per litter) and viviparous
(2–20 pups per litter), the exact method in weasel sharks is unknown but they do
1 Introduction