Researchers say they have found ancient dens of giant carnivorous worms

Twenty million years ago, the shores of northern Taiwan were sandstone sediments on the sea floor, where 6-foot-long worms hid in their burrows, waiting for unsuspecting prey to pass by. above the seare. Now, a team of geoscientists have chronicled 319 fossil traces of these carnivorous marine worms, whose dens fossilized in Miocene mud.

“At first, we were very convinced that this was a very sophisticated shrimp burrow,” Ludvig Löwemark, sedimentologist at National Taiwan University, said on a video call. “And then, after discussing with other experts, we looked at this bivalve hypothesis. But in the end, we became more and more convinced that it was actually a bobbit worm that made this trail.

Fossil traces are remnants of the creatures that made them – footprints and other hardened remains of the movements of animals in life, rather than the fossil remains of the creatures themselves. The worms that researchers suggest once inhabited in these burrows are long gone, presumably made up of soft tissue that deteriorated soon after death. An analysis of the fossils is published today in the journal Scientific Reports.

The Löwemark team, led by Yu-Yen Pan from National Taiwan University, discovered hundreds of pockmarks on the rocky coastline of Taiwan. They found that the holes twisted horizontally as they sank, forming a boomerang-shaped burrow about 1 inch wide and 6 feet deep. The tapered curvature of the burrow suggested to the team that the earth beneath the creature was becoming more difficult to dig to a certain depth or was becoming more anoxic. (Worms breathe through their skin, so if the soil they are immersed in does not contain enough oxygen it can be fatal).

Where the burrows opened up to the then seabed, there was a ‘plumage’ pattern the team identified, which suggested that the silty sea floor had collapsed around the structure in. funnel-shaped, indicating a void left by a creature retreating into its lair. They concluded that the animals that made the burrows are close relatives of today’s killer worms, which are still up to 10 feet long and were named after an infamous Criminal case from the 1990s involving a cut penis (although it may be time to change this name). Traces of fossils in Taiwan are called Magnificent Pennichnus!, which means “beautiful trace of feathers”, the latter name deriving from the Portuguese name for Taiwan, Formosa.

“It doesn’t matter who made it, it’s the form and function of the fossil record that has a name,” Löwemark said. “So you have a genus for similar traits, fossils that were produced in a specific way, due to feeding behavior or locomotion or whatever… and then you have a species name.

After eliminating the other culprits, the shrimp would have left “half-turn” branching chambers in their dens, while the worms are more of a one-way operation, and a suspicious bivalve would have had a dead end. the end of the burrow marking where it made room for its shell – a predatory ambush worm seemed to fit the profile. Today, the bobbit worm hunts by sensation: when it detects a disturbance outside its lair, the worm rushes on the still unidentified organism, armed with hardened pincers. When it has a good grip, the worm pulls the prey into its burrow and the sand collapses above the entrance, hiding the grisly scene. If you blinked, you would never know it happened.

“It’s a very brutal procedure,” Löwemark explained.

When you think about it on a large scale – the team found hundreds of these burrows at two sites along the coast – it looks like a terrifying, inverted game of whack-a-mole.