A brachiopod shell fossil (middle) with protomerithion attached (top).This is part of a new study
Zhang Xiguang
The 515-million-year-old fossil, once thought to be the oldest known animal in a group called bryozoids, may actually be seaweed.
Bryophytes, commonly called bryophytes, are small coral-like creatures that live in sea and freshwater colonies.
Nearly all major animal groups first appear in the fossil record during an evolutionary event known as the Cambrian explosion, 541-520 million years ago. Until two years ago, bryozoans were the only animal group lost from the event. The earliest fossil traces of bryozoans date back 40 million years.
But in 2021, Paul Taylor and his colleagues at London’s Natural History Museum identified Cambrian fossils. Protomerization Gatehouse, Found in Australia and China as a moss.
Martin Smith and his colleagues at Durham University, UK, are now conducting 12 new studies. protomerismIt is like a fossil from Kunming, China, preserved in a way that preserves soft tissue.
The team found that the individual tubular structures were clustered together to form a honeycomb. This can occur in both plants and animals. However, no tentacles or regularly shaped holes through which tentacles pass were seen. This is a sign found in fossils of later bryophytes, says Smith. Instead, researchers noticed long protrusions that look like flanges emanating from the honeycombs, a structure typical of certain types of green algae.
“See those little conical flanges?” he says. “It’s not a good way to be an animal, but it’s a very good way to capture sunlight and do photosynthesis. These are seaweeds.
Specifically, the organism appears to be part of the order Dasycladales of green algae, he says.
Taylor, who was not involved with the new study, says it’s an “interesting and important discovery” that adds to the “jigsaw puzzle” on Cambrian marine life, but doesn’t necessarily prove it. Protomerition Gatehouse They weren’t animals.
In particular, he said that the new fossils were really protomerismespecially since there is a large difference in the size of the structure of the specimens.
Sarah Pruss of Smith College in Northampton, Massachusetts, also has doubts about this. “Their whole claim seems to hinge on this new fossil they’ve found is the same one that had been discovered before,” she says. “That gave me pause.” .”
Even if it were the same, the long processes are likely to be the bryophyte’s tubular structures, and the soft tentacle tissue may simply not be fossilized, says Taylor. It’s not surprising,” he says.
It also doesn’t make any sense, says Pruss. “For paleontologists, no evidence is never good evidence,” she says.
If the fossils are indeed algae, this could actually help better explain the environment that underpinned the Cambrian explosion, says Smith. It’s a great habitat that can support your body plan,” he says.
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