Page last updated at 13:20 GMT, Monday, 4 August 2008 14:20 UK

Ancient shark had colossal bite

By Jennifer Carpenter
Science reporter, BBC News

Meg (S/Wroe/CBRG)
Image showing stress on the megalodon's jaws

The great white shark may have awesome jaws but they are nothing compared with those of megalodon, its gigantic, whale-eating ancestor.

A new study of the extinct creature's skull shows it had an almighty bite, making the prehistoric fish one of the most fearsome predators of all time.

All the more remarkable, scientists say, because the crushing force came from jaws made of cartilage, not bone.

The researchers report their skull work in the Journal of Zoology.

The Carcharodon megalodon super-shark swam in the oceans more than a million-and-a-half years ago.

It grew up to 16m (52ft) in length and weighed in at 100 tonnes - 30 times heavier than the largest great white - and must have been one of the most formidable carnivores to have existed.

"Pound for pound, your common house cat can bite down harder, " explained Dr Stephen Wroe of the University of New South Wales, Australia. "But the sheer size of the animal means that in absolute terms, it tops the scales."

Measuring up

Dr Wroe's team used a technique known as finite element analysis to compare the skulls of the great white with that of the prehistoric megalodon.

The approach is a common one in advanced design and manufacturing, and allows engineers to test the performance of load-bearing materials, such as the metal in the body and wings of an aeroplane.

CT (X-ray) scans were taken of megalodon remains to construct a high-resolution digital model.

A model of a modern 2.4m-long male great white shark (Carcharodon carcharias) was developed for comparison.

Artist's impression: Megalodon (BBC)
A recent BBC series imagined a face-to-face encounter

The model of Megalodon's muscles was based on those of the great white, and the simulations were then loaded with forces to see how the two skulls, jaws, teeth and muscles would have coped with the mechanical stresses and strains experienced during feeding.

By looking at the distribution of stress and strain on the sharks' jaws, researchers found that the largest great whites have a bite force of up to 1.8 tonnes, three times the biting force of an African lion and 20 times harder than a human bites.

Megalodon, though, is more impressive. It is estimated to bite down with a force of between 10.8 to 18.2 tonnes.

The team said biting with such force was quite a feat given that the jaws of these ancient creatures were made of flexible cartilage.

In contrast to most other fish, sharks' skeletons are made up entirely of cartilage. Scientists think that cartilage, being a much lighter material than bone, is one adaptation that allows sharks to swim without the aid of a swim bladder.

With finesse

The Australian research team was interested in how a cartilaginous jaw performs compared with a bone jaw.

The scientists' study shows that the cartilaginous jaw is almost as strong as a bony jaw of the same size - losing only a few percent - in measures of bite force. What is more, the elasticity of the cartilage jaw increases the gape of the sharks to devastating ends.

"The shark's upper jaws can be dislocated: the whole upper and lower jaw pull out and forward as the shark twists and shakes its head from side to side to bite a chunk out of its prey," explains Dr Wroe.

These sharks feed on very large prey: the great white shark eats sea lions and the megalodon is thought to have eaten whales.

"These sharks ambush their prey and immobilise them with a bite, then wait for them to die," Dr Wroe told BBC News. "They are actually delicate feeders and take care not to damage their teeth by biting down too hard on the large bones of their prey."

To keep their teeth sharp, sharks have a battery of them that is continually replaced.

It is the combination of their size, their razor-sharp teeth and the element of surprise that makes these sharks such deadly predators.

MEGALODON COMPARED WITH THE GREAT WHITE SHARK

Shark graphic

Megalodon Great white shark

Type
Cartilaginous fish Cartilaginous fish

Size
16m (52ft) 6m (20ft)

Diet
Whales, including the now extinct Odobenocetops, seals Fish, turtles, seals, sea lions, squid and crustaceans

Predators
None known Occasionally caught by fishing industry as bycatch




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