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Greenland Fossils Show Cambrian ‘Squid’ Were Ancestors of Arrow Worms

Exceptional preservation of ventral ganglia in Greenland fossils provides definitive proof of their arrow worm ancestry

Overview

  • The July 2025 Science Advances paper presents analysis of 25 exceptionally preserved nectocaridid specimens from the Sirius Passet Lagerstätte in North Greenland.
  • Researchers identified a ventral ganglion structure unique to chaetognaths, overturning the 15-year-old hypothesis that nectocaridids were early cephalopods.
  • Discovery of complex camera-type eyes in these fossils indicates they were sophisticated predators occupying high trophic levels during the Cambrian Explosion.
  • Presence of Isoxys arthropod carapaces in the digestive tracts of several specimens confirms a carnivorous diet among these ancient arrow worm relatives.
  • The new species, Nektognathus evasmithae, honors Professor Eva Smith and sets the stage for further studies on chaetognath evolution and Cambrian food webs.