Scientists discover half-billion-year-old prehistoric jellyfish fossil

The oldest species of swimming jellyfish discovered by scientists in fossils half a billion years old. A new species, named Burgessomedusa phasmiformis, was found in Canada and is exceptionally well preserved.

The oldest species of swimming jellyfish ever recorded has been found in fossils dating back 505 million years, scientists say.

According to The Guardian, the fossils were found at Burgess Shale in Canada, an area known for the large number of well-preserved fossils found there.

The new species, called Burgessomedusa phasmiformis, resembles a large swimming jellyfish with a saucer or bell-shaped body up to 20 cm high. Its approximately 90 short tentacles would allow it to capture large prey.

Jellyfish belong to a subgroup of cnidarians, the oldest living group of animals called medusozoans. They are 95% water and decompose quickly, so fossils are rare, but specimens found in the late 1980s and early 1990s are exceptionally well preserved.

In the 1980s and 1990s, scientists discovered the exceptionally well-preserved remains of a range of marine organisms, including jellyfish, in the Burgess Shale, a fossil-rich deposit in the Canadian Rockies.

“The Burgess Shale is known for its incredible conservation quality, including animals that still have eyes, stomachs and intestines, sometimes with food leftovers inside,” says Joe Moysiuk of the University of Toronto in Canada.

“To find such incredibly fragile animals preserved in the rock layers on top of these mountains is such an amazing discovery,” said Dr. Jean-Bernard Caron, curator of invertebrate paleontology at the Royal Ontario Museum and co-author of a study published in Proceedings of the Royal. Society b.

Due to the rarity of jellyfish fossils, their evolutionary history has been largely studied through microscopic fossilized larval stages and results from molecular studies of living jellyfish.

Jellyfish, along with their relatives, were “surprisingly difficult to identify in the Cambrian fossil record,” according to Joe Moisuk, co-author of the study, despite being part of one of the earliest animal groups.

The discovery of Burgessomedusa phasmiformis showed that the Cambrian food chain was much more complex than previously thought, he says. “This discovery leaves no doubt that they were swimming nearby at the time,” notes Joe Moysiuk.

The ancient animal looks very much like a modern jellyfish, says Moysyuk. Its length is 20 centimeters, it has a large bell-shaped body and more than 90 tentacles at the edges. The prehistoric jellyfish was caught in an underwater mudflow, New Scientist notes, adding that jellyfish have a complex life cycle in which they take on two distinct forms: polyps and jellyfish. At the polyp stage, which is one of the first stages in the life of jellyfish, they live on the sea floor and reproduce asexually. They then turn into jellyfish, which are free to swim and mate with other jellyfish.

Previous excavations have revealed polyp fossils dating back 560 million years. “But this is the first time that we have incontrovertible evidence of a large swimming jellyfish during this time,” Moysiuk says, suggesting that jellyfish evolved this life cycle at least half a billion years ago.

Jean-Bernard Caron says, “This adds another remarkable animal lineage preserved in the Burgess Shale that chronicles the evolution of life on Earth.”