The discovery has changed the way researchers think about the distant past
Ancient species of swimming jellyfish discovered by scientists in fossils half a billion years old. The new species, named Burgessomedusa phasmiformis, was found in Canada and is exceptionally well preserved.
According to scientists, the oldest species of swimming jellyfish ever recorded was discovered in fossils 505 million years old.
The fossils were found in Burgess Shale, Canada – in an area famous 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. About 90 short tentacles would allow him 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, writes The Guardian.
In 1980 In the 1990s and 1990s, scientists discovered 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 preservation quality, including animals that still have eyes, stomachs and intestines, sometimes with leftover food inside,» says Joe Moysiuk of the University of Toronto in Canada.
“The discovery of 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 the journal 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 molecular studies of living jellyfish.
According to Joe Moisuk, co-author of the study, jellyfish, along with their relatives, were «surprisingly difficult to identify in the Cambrian fossil record,» despite being part of one of the earliest animal groups.
According to him, , the discovery of Burgessomedusa phasmiformis showed that the Cambrian food chain was much more complex than previously thought. «This discovery leaves no doubt that they were swimming nearby at the time,» notes Joe Moysiuk.
The ancient animal looks very similar to the modern jellyfish, says Moysyuk. Its length is 20 centimeters, it has a large bell-shaped body and more than 90 tentacles along the edges. A 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 seabed and reproduce asexually. They then turn into jellyfish that can swim freely and mate with other jellyfish.
Previous excavations have unearthed 560-million-year-old polyp fossils. «But this is the first time we have hard 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 wonderful lineage of animals preserved in the Burgess Shale that chronicles the evolution of life on Earth.»