Page 64 - World of Animals - Book of Sharks & Ocean Predators

Sharks & Ocean Predators
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Prehistoric

sharks

Get ready for the bone-chilling
ancestors of modern sharks

The waters of prehistoric Earth were as wild and exotic as the land, so
few creatures survive that can claim a lineage that goes back as far as
sharks. Their design has been so successful that the ancestors of the
first sharks still thrive today, 350 million years later, having endured

several extinction events and outlived the dinosaurs. Here are fi ve of
their most interesting evolutionary checkpoints along the way.

Megalodon

The mega-mouth of the ancient world
The fossilised teeth from this fearsome giant of prehistoric waters are so big that
up until the seventeenth century, they were thought to be dragon tongues, turned
to stone! Megalodon had a similar biting style to modern day great whites, but it was much, much bigger. The reason for
its enormous size? Unlike modern sharks, Megalodon hunted the biggest prey in the ocean – cetaceans like whales that
were much more numerous millions of years ago. Compression damage in the vertebrae of Megalodon suggests that it
could have attacked from below, slamming into the whale’s body and stunning it, before dealing the killing bite.

Stethacanus
The anvil-fi nned tiddler
Some of the ancient ancestors of modern sharks are real curiosities, like
Stethacanus: at around half a metre (1.6 feet) long, you’d hardly swim
for your life if you encountered it today, but you might pause to

consider its odd-looking dorsal fin. Protruding from its back in
the shape of a large anvil, it was covered in small spikes, and
was thought to reduce drag in the water and allow Stethacanus

to swim more efficiently. A pair of tendrils trailed from the rear of

its pectoral fins and males of the species had larger spikes, but no one
knows exactly what their purpose was. Stethacanus had similar feeding habits

to modern sharks, eating the fish and cephalopods (such as squid) of the era.

530mya ~ First Fish appear 250mya ~ Mother of mass extinctions
During an era known as the An extinction event even bigger than the one
Cambrian explosion, when most that killed the dinosaurs happened around
animals first appeared, jawless fi sh this time, which killed 99 per cent of marine

evolved to dominate the seas. life. Sharks survived it.

350mya ~ First sharks evolve 231-66mya
Nearly 200 million years of evolution ~ Dinosaurs lived and died
later, a weak-jawed and small but The dinosaurs arose, ruled and died
successful design for sharks is during this period but once again, sharks
established in the form of Cladoselache. survived the extinction event.

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