Giant predatory marine worms that lived about 20 million years ago ambushed their prey by jumping over them from underground tunnels under the sea, reveal new fossils from Taiwan.
These monstrous worms may have been the ancestors of modern Bobbit worms (Eunice aphroditois), which also hide in burrows under the ocean floor and can reach 3 meters in length. Based on fossil evidence from Taiwan, the dens of the ancient worms were L-shaped and about 7 feet (2 m) long and 0.8 to 1.2 inches (2 to 3 centimeters) in diameter, the researchers recently reported in a new study.
The soft bodies of such ancient worms are rarely preserved in the fossil record. But scientists found fossilized marks, also known as traces of fossils, left by the worms; some of these marks were probably made while dragging prey for destruction. The researchers collected hundreds of these impressions to reconstruct the worm tunnel, the oldest known fossil trace of an ambush predator, according to the study.
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Bobbit worms are polychaetes, or bristle worms, that have been around since the beginning Cambrian period (about 543 million to 490 million years ago), and their hunting habits were fast and “spectacular”, the scientists wrote. Modern Bobbit worms build long tunnels to accommodate their bodies; they hide inside and then launch themselves to grab the prey between their jaws, pulling the struggling creature into the underground lair to eat. This “terror from below” grabs and pierces its prey with sharp tweezers – sometimes cutting them in half – and then injects toxins to make the prey easier to digest, according to Smithsonian Ocean.
The researchers examined 319 remains of fossilized tunnels in northeastern Taiwan; From these features, they reconstructed long, narrow burrows that resembled those made by modern long-bodied Bobbit worms. And the details preserved in the rock suggest how ancient predatory worms may have used these burrows, according to the study.
“Our hypothesis is that about 20 million years ago, on the southeastern border of the Eurasian continent, the ancient Bobbit worms colonized the seabed waiting in ambush for a passing meal,” reported the study authors. Worms “exploded” from their burrows as the prey approached, “grabbing and dragging the prey into the sediment. Below the sea floor, the desperate prey struggled to escape, leading to further sediment disturbance around the opening of the den “, wrote the scientists.
As the ancient worms retreated deeper into their tunnel with the struggling prey, the fight stirred the sediment, forming “feather-like collapse structures” that were preserved in the remains of fossils. The researchers also detected pockets rich in iron in disturbed areas near the top of the tunnels; these probably appeared after the worms reinforced the damaged walls with layers of sticky mucus.
Although no fossilized worm residues have been found, scientists have identified a new genus and species, Pennichnus formosae, to describe ancient animals, based on the distinct shapes of their dens.
The likely behavior that created the tunnels “records a life and death struggle between predator and prey and, indirectly, preserves evidence of [a] Paleo-ecosystem more diverse and robust than can be interpreted from the fossil and the fossil record only “, reported the study authors.
The findings were published online January 21 in the newspaper Scientific Reports.
Originally published on Live Science.