Simon Fraser University researchers have found evidence that large ambush predators – some as long as two meters – roamed the ocean floor near Taiwan more than 20 million years ago. The finding, published today in the journal Scientific reports, is the result of the reconstruction of an unusual trace fossil that they identified as a hollow of these ancient worms.
According to lead student of the study, SFU Earth Science PhD student, Yu-Yen Pan, the trace fossil was found in a rocky area near the coast of Taiwan. Trace fossils are part of a research field known as ichnology. “I was fascinated at first glance by this monster tree,” she says. “Compared to other track fossils, which are usually only a few tens of centimeters long, this one was large; two meters long and two to three centimeters in diameter. The characteristic, feathery structures around the upper cavity were also unique. track fossil has not shown similar properties. ‘
Pan and SFU Earth Science professor Shahin Dashtgard are part of an international team that has named the homes of these old giant worms. Pennichnus formosae. Pan began the work while completing her M.Sc. degree under the supervision of Professor Ludvig Löwemark, from the Department of Earth Sciences at the National Taiwan University, Taiwan.
After investigating 319 samples preserved in the early Miocene layer (22 million – 20 million years ago) in northeastern Taiwan, the morphological model of this trace fossil was built.
“Shahin encouraged us to reach out to marine biologists, marine photographers and aquarium conservationists to compare the holes with biological analogues, which enabled us to conclude that this trace fossil is produced by giants, ambush predators, Says Pan.
The modern-day Bobbit worm, which is also large and predatory, is sometimes called the ‘sand-striker’. He preys with his antennae, then grabs them with his powerful jaws and pulls back into his hollow. When it digs, the body covers the entire cavity which explains the two meter long cavity observed in Pennichnus.
Further analysis revealed that a high iron concentration occurred around the upper spade, leading researchers to believe that the worm secretes mucus to strengthen and rebuild the burial wall after each feeding.
Modern Bobbit wormholes are similar to those of Pennichnus, suggesting that the sediment collapsed in the cave after retreating or pulling still live prey under the seabed.
Red worms in the sea have existed since the early Paleozoic (> 400 million years ago), but their soft tissue bodies decay and leave little trace of their existence. Pennichnus formosae is thought to be the first known trace fossil to be produced by an obnoxious predator beneath the surface, giving researchers a rare opportunity to learn more about the behavior of this ancient sand attacker.
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