A fossilized ventral ganglion reveals a chaetognath affinity for Cambrian nectocaridids
- Jakob Vinther
- Luke A. Parry
- Mirinae Lee
- Morten Lunde Nielsen
- Yeongju Oh
- Changkun Park
- Ji-Hoon Kihm
- Giacinto DeVivo
- David A. T. Harper
- Arne T. Nielsen
- Tae-Yoon S. Park
2025-07-23
Nectocaridids are enigmatic Palaeozoic animals with a controversial phylogenetic position. Previous hypotheses have placed them in their own phylum, chordates, molluscs (specifically cephalopods), or radiodont panarthropods. We describe here a nectocaridid, Nektognathus evasmithae gen. et sp. nov. from the early Cambrian (~519 million years) Sirius Passet Lagerstätte of North Greenland. Key specimens preserve paired, phosphatized arcuate structures consistent with preservation of a ventral ganglion, a feature characteristic of extant and fossil chaetognaths, including the amiskwiid Timorebestia koprii also from Sirius Passet. Nektognathus shares a gnathostomulid-like jaw apparatus, lateral fins, subterminal anus, and large antennae with Timorebestia and Amiskwia , placing nectocaridids in the chaetognath stem lineage. The complex sensory anatomy of nectocaridids, which is partially shared with other extinct amiskwiids, highlights a more dynamic predatory lifestyle much higher in the trophic food chain during early chaetognath evolution.