A Canadian PhD Student Helped Uncover a 450-Million-Year-Old Jellyfish Relative

Soft-bodied animals rarely leave a clear fossil record, but dozens of delicate remains in Quebec limestone have revealed an unusual relative of modern jellyfish that lived about 450 million years ago.

Greta Ramirez-Guerrero, a PhD candidate at the Université de Montréal, led the study of Paleocanna tentaculum. The animal did not resemble the drifting jellyfish familiar today. It was a polyp with an elongated body enclosed in a narrow tube and a ring of tentacles at one end.

The team found around 135 individuals spread across 15 slabs of shaly limestone from the Upper Ordovician Neuville Formation. Researchers measured and photographed 39 specimens in detail, then compared their physical features with 69 fossil and living species related to jellyfish. That broader comparison helped them determine where the new genus and species belonged among ancient medusozoans.

The analysis placed Paleocanna tentaculum as an early-branching member of the medusozoan crown group. It indicated that the species was more closely related to the group that includes modern cubozoans, scyphozoans and staurozoans than to some other fossil medusozoans. The arrangement of the fossils also provided clues about how quickly the animals were buried and how their soft bodies left carbonaceous impressions behind.