The underwater lair of a giant worm that ambushed passing sea creatures 20 million years ago has been discovered by fossil hunters in Taiwan.
Researchers believe the 2-meter-long burrow found in ancient marine sediment was once home to a prehistoric predator that erupted from the seabed and dragged unsuspecting animals to its lair.
The creature may have been similar to today’s ferocious “Bobbit Worms” that lurk in sandy burrows on the seabed with antennae sticking out to detect passers-by. Although gentle, worms possess sharp, powerful jaws that can cut a fish in half.
“After 20 million years, it is not possible to say whether this was done by an ancestor of the Bobbit worm or another predatory worm that worked more or less the same way,” said Professor Ludvig Löwemark , sedimentologist at National Taiwan University. “There are huge variations in the behavior of the Bobbit worm, but it looks very similar to the shallow water worms that reach, grab fish and pull them down.
To Bobbit, or Eunice aphroditois, take their names from the John and Lorena Bobbitt case, in which the latter – after years of physical and sexual abuse – cut the former’s penis with a kitchen knife.
Löwemark and his colleagues discovered the fossilized lair and others like it while studying 20-meter-old sedimentary rocks on Taiwan’s northeast coast. Burrows are reinforced with mucus and are more weather resistant, which means they sometimes protrude through fine sandstone walls.
Scientists were initially mystified by the traces of fossils, but gradually converged on a probable suspect. At the top of the 3cm wide burrows, they noticed a distinctive pattern that looked like several inverted funnels stacked on top of each other. This gave the den opening a feathered appearance in cross section.
After ruling out other burrowing creatures such as shrimp and the marks left by stingrays exploding the seabed with jets of water to expose curled up prey, the researchers concluded that the feathered entrance to the lair was caused by a hunting strategy similar to that of the Bobbit worm.
When the worms pull their prey to their lair, the top of the burrow collapses and the worms must rebuild it before they ambush their next meal. “This results in the stacking of conical structures in the cone that form the ‘feathers’ around the highest part of the tube,” Löwemark said.
Writing in the journal Scientific Reports, the researchers describe 319 shallow-water burrows preserved in 20m-old sandstone in Yehliu Geopark and on the nearby Badouzi Headland, suggesting that the local seabed has been colonized by beasts. Traces of fossil burrows, named Pennichnus pretty; are vertical for the top meter, then horizontal for another meter or so, perhaps because the deeper sediments are more difficult to dig and the water there is less oxygenated. Bobbit worms breathe by absorbing oxygen through their skin.
The researchers were hoping the burrows might contain fossilized remains of prey or the worms themselves, but they haven’t found any so far. One reason, Löwemark said, is that burrowing worms often inject their droppings into the water and let it run away, spreading bone fragments from previous meals far and wide.
Löwemark has a dream of one day studying Bobbit worms in the wild. “They are awesome animals,” he says. “You don’t necessarily want to dive too close if you find one.”