2023-08-07 13:15:24
Jellyfish belong to the set of medusozoans, and include the box jellyfish (cubomedusae), hydroids, stauromedusae, and today’s true jellyfish. Jellyfish are part of one of the oldest groups of animals, called Cnidaria, a group that also includes corals and sea anemones.
Cnidarians have complex life cycles with one or two body shapes, a cup-shaped body, called a polyp, and in medusozoans, a bell- or saucer-shaped body, typically identified with jellyfish, that may or may not be free-swimming. .
While fossilized polyps have been known to exist in 560-million-year-old rocks, the origin of swimming jellyfish has long been a mystery. This has been greatly contributed to by the fact that fossils of any type of jellyfish are extremely rare, making it difficult to preserve their body shape.
From fossil traces of 505 million years ago, a species of jellyfish capable of swimming (the best known) has been discovered that has received the name Burgessomedusa phasmiformis. This species has now become the oldest known of all jellyfish capable of swimming.
The study of the fossils has been carried out by Justin Moon and Jean-Bernard Caron, from the Royal Ontario Museum, and Joe Moysiuk, from the University of Toronto, both institutions in Canada.
Artist’s impression of a group of jellyfish of the Burgessomedusa phasmiformis species swimming in marine waters from the Cambrian period. (Illustration: © Christian McCall)
The Burgessomedusa phasmiformis find shows unequivocally that large swimming jellyfish with a saucer- or bell-shaped body already existed more than 500 million years ago.
The fossil remains were found in the Burgess Shale paleontological site in British Columbia, Canada.
Fossils of Burgessomedusa phasmiformis are exceptionally well preserved, especially considering that jellyfish are made up of approximately 95% water.
The study is titled “A macroscopic free-swimming jellyfish from the middle Cambrian burgess shale”. And it has been published in the academic journal Proceedings of the Royal Society B Biological Sciences. (Source: NCYT from Amazings)
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