2023-08-05 02:08:28
Discovered at the Royal Ontario Museum
Last Updated Saturday, 5 August 2023 – 02:08
More than 500 million years ago these creatures were already efficient predators that swam in the oceans of the Earth, with tentacles up to 20 centimeters long.
Two specimens of jellyfish of different sizes Jean-Bernard Caron
95% of its body is made up of water and in addition to being one of nature’s most unusual creatures, it is also one of the most successful despite its apparent fragility. The next time you come across a jellyfish, consider that they have been plying the oceans for hundreds of millions of years. At least, for 505 million years, since that is the dating of the oldest fossils of swimming jellyfish discovered so far.
This is confirmed by a team of scientists from the Royal Ontario Museum, in Canada, who unknowingly kept in their collection fossils so old of a species of jellyfish unknown until now that it has been baptized Burgessomedusa phasmiformis. Although jellyfish and their relatives are believed to be one of the earliest animal groups to evolve, it has been difficult to place them in the Cambrian fossil record (a period that extends from 539 million years to 485 million years ago).
Artistic reconstruction of ‘Burgessomedusa phasmiformis’Christian McCal
As Jean-Bernard Caron, co-author of the study and curator of Invertebrate Paleontology at the Royal Ontario Museum, explains to this newspaper, The Burgess Shale deposit was discovered in 1909. but these jellyfish fossils were collected almost 80 years later by the Royal Ontario Museum under research and collecting permits from Parks Canada. “Although these fossils were discovered decades ago, they had never been formally described or studied.“, adds via email his colleague Joe Moysiuk, co-author of this study published this week in the journal Proceedings of the Royal Society B Biological Sciences. “There is always a conflict between the need to wait to see if more can be discovered fossils and just do the job. After all this time, it’s exciting to finally give these fossils the attention they deserve,” he says.
According to the dating carried out, they would be the oldest confirmed swimming jellyfish: “Aside from Burgessomedusa, the next oldest definitive large jellyfish comes from the late Cambrian period, and is about 10 million years younger. These fossils are just impressions, so they provide very few details. There are also some slightly older fossils of microscopic larval forms that suggested that this group of animals might have an earlier origin, but now we have conclusive proof,” Moysiuk says.
Caron admits, however, that the fossil record of jellyfish is controversial: “Prior to the discovery of Burgessomedusa, the oldest published jellyfish body fossil was a fragmentary, poorly preserved 518 million-year-old specimen found at the Chinese Chengjiang Biota Site. We reinterpreted this fossil as a mound-like organism.” ctenphore (or comb jellyfish), a different group of animals unrelated to jellyfish Younger fossils found in Utah, USA, and about the same age as the Burgess Shale (505 million years old), they were also redescribed as ctenphore-type fossils in our article. Older microscopic fossils from China, from 535 million years ago, probably didn’t swim.”review.
“The key point here is that Burgessomedusa unequivocally represents the oldest macroscopic swimming jellyfish in the fossil record. The term ‘swim’ here is critical,” says Caron.
Poison
Regarding the resemblance of Burgessomedusa to modern jellyfish, Joe Moysiuk points out that “shares characteristics with several modern groups, but does not fit perfectly into any of them. For example, its cubical shape resembles that of modern box jellyfish (or sea wasps), some of which are famous for their deadly stings. The arrangement of the tentacles around the entire margin of the bell-shaped body is more similar to modern members of the true jellyfish group, such as moon jellyfish. Although we are pretty sure that Burgessomedusa is a member of the Medusozoa, we are not so sure which group of jellyfish it is most closely related to“, shift.
Excavations at the Burgess Shale site in 1992 Desmond Collins
Was it a poisonous jellyfish? The authors of the discovery suspect so but are not sure. As Caron explains, “jellyfish belong to the cnidarian group, which also includes corals and sea anemones. The cnidarians are united by having stinging cellscalled cnidocytes, however, such cells are not preserved in fossils and can only be inferred.”
“While they primarily use this venom to catch smaller prey, in some species it can be powerful enough to kill much larger organisms, including people. We strongly suspect that Burgessomedusa would have had venom based on its relationship to modern jellyfish. However, We don’t know how powerful it would have been.”admits for his part Moysiuk.
Regarding its possible prey, the researcher states that they have a specimen in which two different arthropods (related to modern spiders and crabs) are apparently preserved inside the Burgessomedusa bell: “However, we are not sure if this is evidence of predatory interaction or a random association. Arthropods and their larvae would have been the most abundant potential prey at this site.”.
Fossils found in Canada that preserve jellyfish from 500 million years ago Jean – Bernard Caron
As Jean-Bernard Caron details, the size of the jellyfish specimens found vary in size and range from a couple of centimeters to more than 20 centimeters: “Given that most animals in the Burgess Shale site are smaller than an adult finger, heThe largest jellyfish specimens were gigantic compared to other organisms living at the same time. in that community. The groups of small and large specimens are reminiscent of jellyfish swarms in modern oceans.”
For Caron, this scientific find made from a museum archive “exemplifies the important role of new field research and collections in increasing our knowledge of the diversity of life that existed after the appearance of animals during the so-called explosion.” cmbrica”.
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