Gun toot my own horn, but I know a thing or two about strange animals. And I can tell you without a doubt the strangest bobbit worm. Growing to 10 feet long, the worm digs a graveyard in the seabed, leaving only its bear trap of mouth sticking out. As a fish approaches, the bobbit worm burns out of its hole with incredible speed, sculpting its jaws around its prey. With brutal tubing, the worm then slides the victim down into its surface, where it eats the live fish. (Oh, there’s a video.)
Now scientists say they have found evidence that the ancestor of the bobbit worm may have threatened fish 20 million years ago. Writing today in the magazine Scientific Reports, the researchers argue that hundreds of fossil worm holes, found in Taiwan today, show sad signs of stress. They didn’t find the worms themselves, mind you, because boneless critters like worms (called invertebrates, because they don’t have spinal columns) rarely fossil. Instead, find them out lorg fossils, geological features that reflect the behavior of ancient animals, in sandstone that was once a bed.
“This is, we believe, the first time we have found trace fossils that show how invertebrates like worms fed on vertebrates,” said sediment expert Ludvig Löwemark. Taiwan National University, coauthor of the new paper. “Typically, what we find in the sedimentary record is animals that move through the sediment.” Invertebrates, for example, can dig tunnels through the seabed and pump water through their holes, filtering out grains. “But this is a record of much more active behavior,” he continues. “The worms were actually hiding in the sediment, jumping out, catching their prey, and then dragging this prey down to the sediment. ”
Sandstone formation in Taiwan, where large worms once hunted.
Courtesy of Ludvig LöwemarkThe fossil holes are about 6.5 feet long. From their openings on the seabed surface, they would have run more or less straight into the mud. Then, halfway down, they would bend at about 45 degrees, forming an L-shape, or boomerang. Near the mouth of the tunnels, Löwemark and his colleagues noticed “falling channels,” or heaps of sediment that had accumulated inside the hole. The researchers argue that this is a sign of conflict, preserved for millions of years in the fossil record: As a worm drags a fish into its surface, sediment would pour in to fill the gap.
A cross-section of a hole is shaped somewhat like a feather, with the main channel as the stem, and the falling channels spreading out in the sediment on either side. The researchers argue that this is an indication of worm feeding habits. “Once the worm has dug up its prey, it will come to the surface again,” says Löwemark. “It re-establishes a tunnel system in the middle of these collapsed structures, which is how the feather-like structures around the tube are formed.”