Page 65 - World of Animals - Book of Sharks & Ocean Predators

Prehistoric sharks
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RIGHT
Helicoprion remains of Helicoprion’s
These fossilised
teeth look remarkably
Saw-toothed mystery shark like an ammonite.
Helicoprion is a real oddity of the ancient ocean and has baffled palaeontologists for over a

century. The point of confusion is its mouth, which doesn’t conform to any modern standard
at all. The structure considered to be its bottom jaw consists of a single blade of teeth that
curve around like a circular saw – what is now known as it’s ‘tooth-whorl’. Fossils of its jaw were

understandably thought to be an exotic kind of ammonite at first, before being
recognised as an appendage of the ancient shark. The lack of wear
the fossil suggests that the saw-jaw could have been used
to cut through prey like fish and octopus.

“Fossils of its jaw were

understandingly
thought to be an

Edestus exotic ammonite”

Serrated, scissor-mouthed terror
It’s no real surprise that Edestus belongs to the same family as the bizarre
Helicoprion: it was a similar shape, grew to a similar size of around six
metres (19 feet) long and possessed an equally strange set of gnashers. The
teeth in both its top and bottom jaw curved outwards along a single ridge,
giving its mouth a scissor-like appearance. How it hunted is still a mystery
as the shape of its jaws would have made it harder to swim, although one
theory is that Edestus would use its powerful frame to charge its prey and
slam its serrated teeth into its side like a spiked mace, which probably would
have been a killing blow.

Cladoselache

Ancient ancestor of all sharks
About 350 million years ago, the first of what scientists

recognise to be ‘true’ sharks emerged. Cladoselache was
the ancestor of them all – to the untrained eye, it more
closely resembled the fish from which it had evolved.

However, on closer inspection, it had a few key
features in common with modern sharks. It was
extremely streamlined, with a fusiform body
that tapered at both ends, and pectoral fi ns
100mya ~ Rise of the modern shark that acted like stabilising hydrofoils as it
Many easily recognisable features of moved swiftly through the water. Unlike
modern sharks, like the mako and modern sharks, the shape of its teeth
porbeagle, can be found on their ancient suggests that Cladoselache merely
ancestors from this period. gripped its prey in its mouth before
swallowing whole. At just over 1.5
metres (5 feet) long, it was far from
the top of the food chain, although it
2mya ~ Megalodon disappears was more than capable of outpacing
The last fossil teeth of Megalodon can its predators.
be traced to around this time, having
terrorised the oceans for over 13
million years.

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