Jellyfish have been floating by way of Earth’s oceans seemingly eternally. However pinning down the precise origin of those squishy sea creatures, that are among the earliest advanced animals, is tough. They hardly ever present up within the fossil document as a result of jellyfish are 95 p.c water and are vulnerable to speedy decay.
“Should you see a jellyfish outdoors of the water, a pair hours later it’s only a ball of goo,” mentioned Jean-Bernard Caron, a paleontologist on the Royal Ontario Museum in Toronto.
However Dr. Caron and different scientists just lately described a cache of jellyfish fossils from the Cambrian interval that discovered an unbelievable pathway to preservation. In a paper printed on Wednesday within the journal Proceedings of the Royal Society B, the scientists posit that these 505-million-year-old animals are among the many oldest swimming jellyfish identified to science.
“These new fossils characterize probably the most compelling proof of Cambrian jellyfish to this point,” mentioned David Gold, a paleobiologist on the College of California, Davis, who was not concerned within the new research.
The jellyfish specimens have been discovered within the Burgess Shale, a fossil-rich web site within the Canadian Rockies that gives a glimpse of life throughout Earth’s Cambrian explosion. Like different soft-bodied creatures discovered on the web site, the gelatinous jellyfish are preserved in gorgeous element. Most nonetheless possess upward of 90 fingerlike tentacles, which stick out of the creature’s bell-shaped physique just like the strings on the finish of a tassel rug. Some even retain their abdomen contents and gonads.
Again within the Nineties, Royal Ontario Museum researchers unearthed greater than 170 jellyfish fossils from the Raymond Quarry in British Columbia. When Dr. Caron and a Ph.D. scholar examined the specimens extra just lately, they realized the fossils represented a brand new species, which they named Burgessomedusa phasmiformis.
The species is a part of a various group referred to as medusozoans, that are thought to have originated a minimum of 600 million years in the past and are nonetheless swimming in the identical seas we all know at present. However proof of their rise is scarce. Most fossils from earlier than the Cambrian interval are both microscopic or little greater than faint imprints, making it tough to deduce how these ancestral jellies lived.
Over the previous 20 years, paleontologists have found a number of well-preserved jellyfish-like fossils from websites in Utah and China which might be related in ages to the Burgess Shale. Nonetheless, the true identities of those creatures remains to be up for debate. Within the new paper, Dr. Caron and his colleagues proposed that the fossils from Utah and China characterize historic ctenophores, or comb jellies, one other group of gelatinous animals solely distantly associated to true jellyfish.
Not all researchers are offered by this reclassification. In line with Bruce Lieberman, a paleontologist on the College of Kansas who studied the Utah fossils, the brand new paper lacks compelling proof to attach the sooner fossils with comb jellies. As an alternative, he thinks Burgessomedusa joins a swarm of jellyfish species that patrolled Cambrian seas. “It actually provides to the compelling physique of proof indicating that medusozoans, that are a extremely vital clade within the oceans at present, have been already established by the point of the Cambrian interval,” Dr. Lieberman mentioned.
The researchers suppose that including jellyfish to the Burgess Shale’s miniature menagerie provides one other layer of complexity to Cambrian ecosystems. With a physique that grew to almost eight inches lengthy, Burgessomedusa was among the many bigger creatures round.
In line with Dr. Gold, Burgessomedusa’s bell-like form is harking back to trendy field jellyfish, that are potent predators that pack a lethal sting. “Field jellyfish are energetic hunters and use their bell for energetic reorientation and bursts of pace to go after prey,” Dr. Gold mentioned. Nonetheless, Burgessomedusa seems to lack a number of sensory constructions present in trendy jellyfish. “It’s unclear if it had the eyes trendy field jellies use to hunt,” Dr. Gold mentioned.
Even with out eyes, Burgessomedusa was prone to have been a high predator. Like trendy jellyfish, it most likely specialised on smaller fare. However it seems to have additionally been able to searching comparatively massive sport: One Burgessomedusa specimen studied within the paper was preserved with a trilobite lodged inside its bell.
The flexibility of jellyfish to seize prey whereas drifting by way of the ocean regardless of being nearly totally composed of water has made them the oceans’ most enduring predators.
“Burgessomedusa demonstrates how little the fundamental jellyfish physique has modified,” Dr. Gold mentioned. “They’ve survived comparatively unchanged for tons of of tens of millions of years.”
