open access publication

Article, 2024

A giant stem-group chaetognath

In: Science Advances, ISSN 2375-2548, Volume 10, 1, 10.1126/sciadv.adi6678

Contributors (13)

Park T.-Y.S. (0000-0002-8985-930X) [1] [2] Nielsen M.L. (0000-0002-4719-6317) [1] [3] [4] Parry L.A. (0000-0002-3910-0346) [5] Sorensen M.V. [6] Lee M. (0000-0003-4415-2447) [1] Kihm J.-H. (0000-0001-8605-6272) [1] [2] Ahn I. [1] [2] Park C. (0000-0002-1206-6803) [1] de Vivo G. (0000-0002-6979-8319) [7] Smith M.P. (0000-0002-5141-1577) [5] Harper D.A.T. (0000-0003-1315-9494) [8] Nielsen A.T. (0000-0001-8194-8546) [9] Vinther J. (0000-0002-3584-9616) [4]


  1. [1] Korea Polar Research Institute
  2. [NORA names: South Korea; Asia, East; OECD]
  3. [2] University of Science and Technology
  4. [NORA names: South Korea; Asia, East; OECD]
  5. [3] British Geological Survey
  6. [NORA names: United Kingdom; Europe, Non-EU; OECD]
  7. [4] University of Bristol
  8. [NORA names: United Kingdom; Europe, Non-EU; OECD]
  9. [5] University of Oxford
  10. [NORA names: United Kingdom; Europe, Non-EU; OECD]


Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here, we describe a large stem chaetognath, Timorebestia koprii gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstätte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to Amiskwia sagittiformis. Amiskwia has previously been interpreted as a total-group chaetognathiferan, as either a stem-chaetognath or gnathostomulid. We show that T. koprii shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in T. koprii suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today.