More than 539 million years ago, soft, clarinet-shaped animals anchored themselves to the seafloor on disc-shaped bases, swaying alongside stalked animals resembling worms and baskets. These woodwindlike creatures are just a few of those coming to life from a treasure trove of newly discovered fossils in southwestern China.
It’s surprising to see some of these weird creatures this far back in the fossil record, and their discovery is unearthing crucial new details about one of the most notable explosions in the diversity of animals in fossil history, researchers report April 2 in Science.
“This paper is absolutely fascinating,” says paleontologist Emily Mitchell at the University of Cambridge. “It provides vital insights into life around the end of the Ediacaran Period.”
The Ediacaran preceded a pivotal moment in animal prehistory called the Cambrian explosion, which started around 539 million years ago and marked a dramatic and rapid diversification, an “explosion” of physical forms and complexity. How that explosion happened isn’t clear. Fossils from the late Ediacaran Period, from 575 million to 539 million years ago, show this is when the first unambiguous animal fossils appear but don’t offer many details about the animals’ bodies or biology. Many of the Cambrian animal groups also do not appear in the Ediacaran record, suggesting that Cambrian animal diversity may have exploded from only a small number of species.
Now, a new trove of fossil specimens collected near Jiangcheng, China, is challenging that idea.
In 2022, Gaorong Li, a paleontologist then at Yunnan University in Kunming, and his colleagues were collecting Ediacaran algae fossils when they noticed some strange, unidentifiable fossil fragments. In 2023, they found preserved cylindrical animals that would have stuck up several centimeters above the seafloor, equipped with a flat pad on one end and a flag-shaped proboscis on the other, one that appears extendable from their mouths. These “bugle worms” were a turning point for the team, Li says.
His team began collaborating with colleagues from the University of Oxford, who joined an expedition in 2024, during which even more late Ediacaran fossils were discovered, totaling roughly 700 across all expeditions.
Comparing the animal fossils to those known from the Ediacaran and Cambrian Periods, Li and the team found specimens that resembled Haootia, formally described in 2014, which dates to 560 million years ago and is the earliest known evidence of muscle tissue in an animal. Haootia and the new find resemble a living martini glass with tentacles on the rim or a stalked coral or jellyfish. Like those modern-day animals, they have body parts that start from a central point, which is called radial symmetry.
Among the more eyebrow-raising findings were the animals with bilateral symmetry — similar features on the right and left sides. Fossilized bodies of bilaterians this early is rare, with only four species known from the Ediacaran until now. Li and the team found more than 180 bugle worm fossils, along with fossils of other bilaterial creatures, including those that looked like sausages on skewers, with feathery appendages around their mouth ends.
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The Haootia -like animal (fossil at left, artist’s reconstruction at right) was possibly a relative of animals like corals, anemones and jellies.
Emmy Smith, a paleontologist at Johns Hopkins University in Baltimore, was struck by the abundance and diversity of bilaterian fossil finds. Many of these show structures specialized for feeding. These weren’t simple progenitors of later lineages; these animals were already quite physically complex, she says. “That strengthens the view that major animal lineages were already diversifying before the Cambrian.”
The results suggest the explosion of animal diversity in the Cambrian didn’t appear out of nowhere, Li says. Instead, a gradual buildup of complex animal life was underway millions of years before.
Figuring out precisely how some of these Ediacaran animals are related to Cambrian groups would be a fascinating next step, says Scott Evans, an invertebrate paleontologist at the American Museum of Natural History in New York City. This might give us a better understanding of where the more familiar Cambrian animals got their evolutionary start.
