A discovery in Canada has unveiled the oldest preserved adult jellyfish ever found, dating back 505 million years, according to the New York Times (NYT). The 182 fossils were found encased within a rock at Burgess Shale fossil site in the country. The discovery is remarkable becaue jellyfish are 95 per cent water and are prone to rapid decay.
Many of the fossils were initially collected at the Burgess Shale in the 1980s and 1990s. Scientists were amazed at the exceptionally preserved remains of various marine creatures, including jellyfish, that are no in the care of Royal Ontario Museum in Toronto.
"If you see a jellyfish outside of the water, a couple hours later it's just a ball of goo," Jean-Bernard Caron, a paleontologist at the museum, told NYT. He described the findings in a paper published on Wednesday in the journal Proceedings of the Royal Society B. It said that these animals are the oldest swimming jellyfish known to science.
The fact that these fossils are indeed that of jellyfish, Joe Moysiuk and his team from the University of Toronto analysed them and identified a groundbreaking specimen. They named it Burgessomedusa phasmiformis, a new species representing the earliest record of an adult jellyfish. Mr Moysiuk describes it as having a ghost-like appearance, resembling the character from the video game Pac-Man due to its unique body shape.
This ancient jellyfish closely resembles its modern counterparts, measuring about 20 centimetres long, with a bell-shaped body and over 90 tentacles around the edge. The jellyfish got caught in an undersea mud flow around 500 million years ago, leading to its rapid burial and exceptional preservation.
Jellyfish have a complex life cycle involving two distinct forms: Polyps and medusas. During their polyp stage, which is one of the initial phases of a jellyfish's life, they dwell on the seafloor and reproduce asexually. Later, they mature into medusas, capable of swimming freely and mating with other jellyfish.
Although 560-million-year-old fossils of polyps were found in previous excavations, this discovery provides the first definitive evidence of a large swimming jellyfish from that time. It suggests that jellyfish had already developed this life cycle at least half a billion years ago.
