If you were suddenly transported to the western Utah of half a billion years ago, treading water near the ocean's shore, you'd be stunned by the alien life-forms surrounding you.
Trilobites scuttle across the muddy bottom. A monster called Anamolacaris glides past, its mouth filled with sharp, grinding teeth and its pair of long, curving claws bristling with spines.
You might be startled by a small creature called Opabinia, an animal with paddles along both sides, a cluster of five eyes and a trunk with a claw on the end.
But scientists now know that among these odd animals were some the time traveler would immediately recognize: jellyfish.
Today jellyfish are known to have flourished in the middle Cambrian seas because of fossil discoveries in western Utah by Richard D. Jarrard, professor, and Susan Halgedahl, associate professor, at the University of Utah. Husband and wife, they undertook the field work of cracking open rocks without outside funding.
On Tuesday, the National Science Foundation announced their discovery of the world's most ancient fossils that can be definitively shown to be of jellyfish.
A scientific report detailing the find, "Exceptionally Preserved Jellyfishes from the Middle Cambrian," was published Wednesday by the journal "PLoS ONE."
"The fossils that they're finding are absolutely wonderful," said Francis H. Brown, dean of the U.'s College of Mines and Earth Sciences and distinguished professor of geology and geophysics. "The detail is exquisite. It really is. I'm really pleased with it."
The find extends the jellyfish line by 200 million years, back to 505 million years ago, during the middle Cambrian era.
Commented Patrick Herendeen, a National Science Foundation program director, "This study clearly shows what paleontologists have long suspected that jellyfish have a history that's much older than the known fossil record."
He noted, according to a NSF press release, "Adding some 200 million years to the age of jellyfish is quite a jump. What's even more surprising is the apparent diversity of jellyfish forms present at that time."
Bruce S. Lieberman, geology professor at the University of Kansas, Lawrence, one of the paper's authors, told the Deseret Morning News that the team that examined the fossils included both paleontologists and biologists who are specialists in cnidarian life, animals like jellyfish and corals.
The biologists were saying, "Yes, you've got this material and it looks so similar to modern things in the cnidarian family," he said.
All representatives of this family have eyes and "this really complex mating behavior," he said. "They're also very active predators, floating around with the plankton."
Halgedahl and Jarrard found four different types of jellyfish, among approximately 45 fossils of the animals that they discovered. Some are like box jellies from Australia.
"We wonder what they're eating out there," Lieberman said. The discovery means that "some of the important predators today in the ocean ... were around 500 million years ago."
Jellyfish either go back further in time, to the mysterious Precambrian era, or they rapidly developed with the start of the Cambrian, he added.
These are the best-preserved jellyfish, "bar none that have ever been found in the fossil record," Lieberman added.
Other fossils have been discovered from different eras that some people think may be jellyfish, but they amount to blobs. "These have muscle scars, gonads and tentacles," he said.
It makes sense that jellyfish might be found in that kind of ocean environment. "But it's a surprise that they look so much like modern jellyfish."
Halgedahl said the first of the specimens was found nearly six years ago. She and Jarrard were uncertain what the black fossil was. It was found in an area with other known types of soft-bodied fossils.
Later, "we kept finding much better-preserved specimens.
"These were in deep water," she said. "They were probably swimming around, hunting food."
After many years of surprising discoveries, she said these may be the most important fossils they have found in western Utah. They sent a group of them to Paulyn Cartwright and Lieberman at the University of Kansas, so they could study them, too. Jarrard said the fossil record has specimens of an amazing variety of organisms, "but it's hard to imagine anything more difficult to create a fossil from than a jellyfish that's less than half an inch in size. ...
"They just don't have any hard parts at all."
The vast majority of fossils found anywhere in the world are of hard objects that survive some time after the animal's death, such as teeth, bones and claws. But a jellyfish is not much more water-filled film.
"The fossils are extremely scarce," Jarrard said.
"Once we found three in about 10 minutes and we thought, 'Boy, what's happened here?"' But typically, they may be on an expedition several days before finding one.
What does it mean that these most ancient jellyfish are so similar to today's?"The general environment of pelagic (open sea) life on the continental shelf must be a really stable environment, for the same body design that was developed back then to have been continuously appropriate all that time.", Washington, D.C.