Glimpse into ancient marine life: 505-million-year-old jellyfish fossil unearthed in Canada

Canada's Burgess Shale fossil site has yielded a groundbreaking discovery – the oldest preserved adult jellyfish ever found, dating back 505 million years. The 182 fossils were remarkably well-preserved within a rock formation, a rarity as jellyfish are composed of 95 per cent water and are prone to rapid decay. Originally collected in the 1980s and 1990s, many of the fossils, including jellyfish, have now found a home at the Royal Ontario Museum in Toronto, where scientists were astounded by the exceptional preservation of various marine creatures.

Jean-Bernard Caron, a paleontologist at the museum, highlighted the challenge of preserving jellyfish, stating that outside of water, they quickly disintegrate into a "ball of goo." However, the fossils in question are indeed jellyfish, a discovery made possible by Joe Moysiuk and his team from the University of Toronto, who identified a groundbreaking specimen named Burgessomedusa phasmiformis. This new species represents the earliest record of an adult jellyfish, characterized by its ghost-like appearance and unique body shape, reminiscent of the video game character Pac-Man.

The ancient jellyfish closely resembles modern counterparts, measuring around 20 centimeters long, featuring a bell-shaped body and over 90 tentacles along its edge. Around 500 million years ago, the jellyfish was caught in an undersea mud flow, resulting in rapid burial and exceptional preservation.

Jellyfish have a complex life cycle involving two distinct forms – polyps and medusas. During their polyp stage, they reside on the seafloor and reproduce asexually. Later, they transform into medusas, capable of swimming freely and mating with other jellyfish.

While previous excavations have uncovered 560-million-year-old fossils of polyps, this latest discovery provides the first conclusive evidence of a large swimming jellyfish from that time. It indicates that jellyfish had already established this life cycle at least half a billion years ago. The findings were published in the journal Proceedings of the Royal Society B, shedding light on the ancient origins of these fascinating creatures.

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