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Saturday, April 20, 2024

Ancient Jellyfish Fossil Reveals Early Evolution of Animals

A discovery in Canada has unveiled the oldest preserved adult jellyfish, dating back 505 million years. The 182 fossils were encased within a rock at the Burgess Shale fossil site in the country, which is known for yielding exceptionally well-preserved marine fossils. Jellyfish are 95 percent water and prone to rapid decay, making their fossils very rare. The fossils are so well-preserved that the researchers could discern features such as the bell shape of the organism, the tentacles, and even muscle scars. The research was published in the Proceedings of the Royal Society B.

Jellyfish are among the earliest animal species to develop. However, it has been challenging to pin down their fossils because they do not have complex parts like teeth or bones that can survive the fossilization process. Fossils of the squishy sea creatures are rarer than any other animals in the Cambrian period, which began about 540 million years ago.

However, the fossils discovered at the Burgess Shale fossil site in western Utah and sent to Paulyn Cartwright at KU and Bruce Lieberman at the University of Kansas were so well-preserved that they could identify a precise jellyfish shape. They also saw tentacles, muscle scars, and possibly gonads, which confirms that the fossils are, in fact, jellyfish. According to a release from KU, the discovery pushes the earliest known occurrence of definitive jellyfish back to the middle of the Cambrian radiation, when most other animal groups first appear in the fossil record.

The new jellyfish fossils are from a previously unknown species of medusa called Burgessomedusa phasmiformis, which belongs to a group of animals known as medusozoans, including modern-day box jellies and hydroids. They resemble the jellyfish you might see swaying in a pond, with long stems topped with cups with tentacles that grab floating plankton. The fossils are remarkably detailed, showing the typical saucer- or bell-shaped body and fourfold symmetry that distinguishes jellyfish from other cnidarians (the group to which corals and sea anemones belong).

“The exquisite preservation of the bodies is truly breathtaking,” the study’s authors said in a press release. “They reveal the remarkable complexity of jellyfish at the onset of the Cambrian radiation.”

The team plans to analyze more fossils from the same rock formation and hopes to uncover further details about the evolution of jellyfish and their relatives. The study’s results could also be used to understand better how proteins, such as those involved in cell aging, work in jellyfish. The findings may help scientists find better ways to treat diseases associated with aging and cancer in humans.

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