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A deep-sea worm that eats the bones of dead whales on the ocean floor has actually been around for 100 million years..much longer than previously thought.

Researchers found holes made by the worms in the fossilised flipper of a a long-necked marine reptile called a plesiosaur.

It could swim faster than an Olympic champion - at 8.2 km/h - but was too slow to catch a mackerel, salmon or seal. They became extinct at the same time as the dinosaurs.

Holes were also found in the rib and shell of an ancient sea turtle.

These holes tell us these scavengers, also known as zombie worms, could have eaten many fossils over decades - making it much harder to work out what animals were alive, hundreds of years ago.

The study's co-author Dr Nicholas Higgs, a researcher at Plymouth University's Marine Institute says

"The worms devoured the skeletons of large marine reptiles that dominated oceans in the age of the dinosaurs. The worms prevented many skeletons from becoming fossilised, which might hamper our knowledge."

Dr Higgs and his colleague Silvia Danise made detailed 3D scans of two holes left in the flipper bone, and four from the sea turtle skeleton. They closely match the holes left in modern whale bones.

This family of worms, was first discovered by a deep sea robot off the California coast in 2002.

They ate animals bodies that fell onto the seafloor. They have been found at depths of up to 4km.

As adults, the finger-length worms have no mouth or digestive system.

They burrow into bones using root-like tendrils and drink up the fatty molecules they need to survive.

But the new research suggests zombie worms must have been around much earlier than previously thought - 100 million years ago, when the huge long necked marine animals roamed the deep.

When they died out, 66 million years ago, they had to start eating sea turtles until whales were created another 20 million years later.