Research Highlights: Researchers Discovered Lair of an Ambush-Predatory Worm from 20 Million Years Ago

Schematic three-dimensional model of the feeding behavior of Bobbit worms and the proposed formation of Pennichnus formosae. Image Source:

Researchers Discovered Lair of an Ambush-Predatory Worm from 20 Million Years Ago

  • Eunicid polychaetes have long, segmented bodies, and strong denticulated jaws.
  • They are widely distributed in tropical to temperate shallow marine to shores.
  • The “Bobbit worm” is one of the largest eunicids that fascinated the public.
  • Burrowing “Bobbit worm” only extend a minor portion of their body outside of the sediment, thus observations on their behavior beneath the seafloor are difficult.
  • However, the feeding behavior of this giant ambush-predator is amazing.
  • “Bobbit worm” hides in burrow and explodes upwards snatching unsuspecting preys with their powerful jaws.
  • The preys are still alive when the “Bobbit worm” pulls them into the sediment for consumption.
  • Ancient predatory polychaetes have soft-tissue bodies resulting in an incomplete fossil record.
  • Nothing is known about the burrows and behavior beneath the seafloor of these ancient polychaetes.
  • Researchers used data from Miocene strata in northeast Taiwan to erect a new ichnogenus, Pennichnus.
  • Ichnogenus is a group of trace fossils that is given a name because the similarity of the traces suggests they were made by closely related species of organisms.[1]
  • Fossil length: 2 meters long
  • Fossil diameter: 2 to 3 centimeter
  • Fossil shape: L-shaped burrow
  • The fossil has distinct feather-like structures around the upper shaft.
  • A comparison of Pennichnus to other biologically similar organisms strongly suggests that this new ichnogenus is related with ambush-predatory worms that lived about 20 million years ago.

Related Research: Smelling Danger – Alarm Cue Responses in the Polychaete Nereis (Hediste) diversicolor (Müller, 1776) to Potential Fish Predation


Pan, YY., Nara, M., Löwemark, L. et al. The 20-million-year old lair of an ambush-predatory worm preserved in northeast Taiwan. Sci Rep 111174 (2021).


Related External Link: Ambush predator – Wikipedia

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