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How ancient 'zombie worms' screwed up valuable fossils

A team of researchers in England has discovered how a worm with no mouth or stomach may have messed with the ocean's fossil record for millions of years.

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A sqadron of Osedax worms chowing down on a whale bone. Plymouth University

In 2002, biologist Robert Vrijenhoek from The Monterey Bay Aquarium Research Institute was searching for deep-sea clams in Monterey Canyon when he came upon strange red worms feeding on a whale carcass. After some lab work, Vrijenhoek and his fellow researchers determined that he had discovered a brand new species of worm, which he called Osedax, and popular culture quickly called it the "zombie worm" because of its penchant for devouring bones. (Yes, you and I both know zombies eat brains, but there you have it.)

Since the discovery, it's been assumed that the worms evolved with whales about 45 million years ago because they're often found chowing down on the bones of dead whales on the seafloor. New research, however, says the red-colored bone eaters evolved a lot earlier than that -- at least 100 million years ago -- when they dined on the bones of prehistoric animals like sea turtles and plesiosaurs (aquatic reptiles with long necks). In doing so, they might have literally devoured much of the fossil record left behind by such animals.

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Researchers say zombie worms attacked plesiosaur fossils like this one. Plymouth Univeristy

"Our discovery shows that these bone-eating worms did not co-evolve with whales, but that they also devoured the skeletons of large marine reptiles that dominated oceans in the age of the dinosaurs," researcher Nicholas Higgs said in a statement. Higgs is a research fellow at the Marine Institute of the UK's Plymouth University who helped make the new discovery. "Osedax, therefore, prevented many skeletons from becoming fossilized, which might hamper our knowledge of these extinct leviathans."

Higgs and his colleagues at the university examined fossil fragments from a plesiosaur found in Cambridge and a sea turtle found in Kent, England. They then used a CT scan to make a computer model of the bones that revealed bore holes that matched up to the trail Osedax would leave in its wake.

The way they produce those bore holes is one of the things that makes Osedax worms especially fascinating. They don't have a mouths or stomachs. Instead, they shoot out "root-like tendrils through which they absorb bone collagen and lipids that are then converted into energy by bacteria inside the worm," says the university.

"The increasing evidence for Osedax throughout the oceans past and present, combined with their propensity to rapidly consume a wide range of vertebrate skeletons, suggests that Osedax may have had a significant negative effect on the preservation of marine vertebrate skeletons in the fossil record," said lead researcher Silvia Danise of Plymouth's School of Geography, Earth and Environmental Sciences.

"By destroying vertebrate skeletons before they could be buried," Danise added, "Osedax may be responsible for the loss of data on marine vertebrate anatomy and carcass-fall communities on a global scale."

Thanks, Osedax.

The researchers' work was published this week in the Royal Society's journal Biology Letters.