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Gigantic predatory marine worms that lived around 20 million years ago ambushed their prey by leaping on them from underground tunnels at the bottom of the sea, new fossils from Taiwan reveal.
These monster worms may have been the ancestors of the modern trap-jawed 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 burrows of ancient worms were L-shaped and were approximately 7 feet (2 m) long and 0.8 to 1.2 inches (2 to 3 centimeters) in diameter, recently have researchers reported in a new study.
The soft bodies of these ancient worms are rarely preserved in the fossil record. But scientists have found fossilized footprints, also called fossil traces, left by the worms; some of these marks were probably made while they were dragging prey towards their destiny. Researchers collected hundreds of these impressions to reconstruct the worm tunnel, the first known fossil record of an ambush predator, according to the study.
Related: These bizarre sea monsters once ruled the ocean
Bobbit worms are polychaetes, or bristle worms, that have existed from the beginning Cambrian period (about 543 million to 490 million years ago), and their hunting habits were rapid and “spectacular,” the scientists wrote. Modern Bobbit worms build long tunnels to accommodate their bodies; they hide inside and rush to grab prey between their jaws, transporting the ailing creature to the underground lair to eat it. This “terror from below” grabs and pierces its prey with sharp pincers – sometimes cutting them in half – then injects toxins to aid the digestion of the prey, according to Smithsonian Ocean.
Researchers examined 319 traces of fossilized tunnels in northeastern Taiwan; from these traces, they reconstructed long, narrow burrows that resembled those made by modern long-bodied Bobbit worms. And details preserved in the rock further hinted at how ancient predatory worms could have used these lairs, the study found.
“We hypothesize that about 20 million years ago, on the southeastern border of the Eurasian continent, ancient Bobbit worms colonized the seabed while ambushing a passing meal,” reported the authors of the study. The worms “exploded” from their burrows as the prey approached, “grabbing and dragging the prey through the sediment. Below the sea floor, the desperate prey waded to escape, resulting in further disturbance of the prey. sediment around the burrow opening, “the scientists wrote. .
As the ancient worms retreated deeper into their tunnel with the beating prey, the struggle stirred the sediment, forming “distinct feather-like collapse structures” that have been preserved in the fossil record. The researchers also detected iron-rich pockets in disturbed areas near the top of the tunnels; these probably appeared after worms reinforced the damaged walls with layers of sticky mucus.
Although no fossilized remains of the worms have been found, scientists have identified a new genus and a new species, Pennichnus pretty; to describe ancient animals, based on the distinctive shapes of their burrows.
The probable behavior which created the tunnels “records a fight to the death between predator and prey, and indirectly preserves evidence of [a] a more diverse and robust paleo-ecosystem than what can be interpreted from fossil data and traces of fossils alone, ”the study authors reported.
The results were published online Jan. 21 in the journal Scientific reports.
Originally posted on Live Science.
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