Here is the ancestor of the Aphroditan Eunice, a giant worm that terrified the oceanic shallows 20 million years ago

A new study suggests that ancestors of the terrifying marine worms scientifically known as Eunice aphroditois (Bobbit worms) colonized the seabed on the southeastern border of the Eurasian continent about 20 million years ago.

These giant predatory worms then lived in a kind of burrow where they waited for prey to pass to emerge from their lairs and attack them in ambush, to then seize them and drag them into the depths of the sediments. Their prey struggling to escape the jaws of these worms caused disturbance of the sediment around the burrow opening.

Here is the ancestor of the Aphroditan Eunice, a giant worm that terrified the oceanic shallows 20 million years ago

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Precisely, one of these burrows was reconstructed by researchers thanks to the careful analysis of fossilized layers of the seabed dating from the same period, which perhaps dates back to the beginning of the Paleozoic. This made it possible to identify this ancestor of the Eunice aphroditois, the Pennichnus formosae. A creature that could measure up to 3 meters in length and also had powerful jaws and sharp mouthparts.

About the ancestor of Eunice aphroditois

The ancestor of the Bobbit worms was therefore identified thanks to the reconstruction of a fossil trace (the trace of an animal, rather than the animal itself) from 319 fossils recovered . A morphological analysis of the fossil trace of Pennichnus formosae was carried out. What led to the reconstruction of a burrow is L-shaped, 2 – 3 centimeters in diameter and galleries of more than 2 meters . The famous signs of disturbance attributable to prey were also noted in the fossil rock disc.

After ruling out other potential inhabitants such as shrimps and mollusks, based on the morphological characteristics of the fossil trace, scientists suggest that this fossil burrow harbored a predatory worm that ambushed its prey. The profile and the traces left would correspond to those of the giant polychaete worms whose current representatives are the Bobbit worms.

In addition, this study of this burrow made it possible to discover that after a hunt, these ancient worms used mucus to rebuild their dens, because a high concentration of iron left by bacteria that fed on this mucus was detected by the paleontologists.

The results of this study were published in the journal Scientific Reports .

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