Controversy erupts over first flower fossil

A small flower pressed between layers of sandstone for more than 160 million years could be the oldest flower fossil ever found, according to a new study.

However, not everyone agrees that the fossil represents an actual flower or is as old as the study claims.

Like modern flowers, the fossils sport sepals and petals, the researchers said. However, its age of 162 million years puts it right in the Jurassic period and in the middle of a heated debate about the origin of angiosperms, the most successful and diverse group of plants in the world. Did angiosperms first bloom in the Cretaceous, or did they exist earlier, in the Jurassic, at the height of giant plant-eating dinosaurs like Apatosaurus?

“People will have to rethink everything about angiosperms because of this fossil,” said study co-author Xin Wang, a paleobotanist at the Nanjing Institute of Geology and Paleontology in China.

Missing branches

Much of the natural history of angiosperms, or flowering plants, appears to be missing from the fossil record. According to fossils, the first land plants were mosses, which appeared about 425 million years ago. Ferns were next, followed by gymnosperms – a group that includes cycads, gingkos and pines. Then, about 125 million years ago, angiosperms and their flowers grew during the Cretaceous period, as fully formed as Aphrodite. In 30 million years, angiosperms would dominate the Earth. [Naughty by Nature: Photos of the Most Disgusting and Deadly Flowers]

Botanists have long wondered how angiosperms and flowers could suddenly bloom without leaving any trace of their ancestry. Charles Darwin called it “an abominable mystery”. Scientists also want to understand the history of this important lineage, because without flowering plants, humans would have no corn or rice, or drugs like morphine.

An artist’s reconstruction of E. panii. (Image credit: Liu & Wang, Historical Biology)

There are hints that angiosperms may have flowered before their first fossils appeared in rocks 125 million years ago. Molecular clocks based on plant DNA suggest that the origins of angiosperms could date back to the Jurassic or even earlier, the Triassic. Tiny pollen grains with characteristics of angiosperms were also extracted from rocks from these ancient times. (To be classified as an angiosperm, a plant must have a closed egg-producing carpel, stamens with pollen sacs, and other traits.)

Because flowers are fragile and difficult to preserve as fossils, perhaps the evidence of absence is simply an absence of evidence. Perhaps angiosperms were the mammals of the Mesozoic – tiny and small, waiting on the sidelines to take over the world, said David Winship Taylor, a plant evolutionary biologist who is lead biology and curator of the herbarium at Indiana University Southeast in New Albany.

“My own feeling is that we’re not looking properly,” said Taylor, who was not involved in the research. Taylor thinks the first angiosperms were small plants, similar to flowering herbs. “I suspect the angiosperms had a little pollen and we’re running out of that,” he told Live Science.

Either way, the newly reported fossil is unlikely to influence strong opinions on either side of the debate. To claim a flower of the Jurassic age, researchers must be absolutely sure of its timing, and in this case, it is impossible. The specimen was collected more than 40 years ago by Kwang Pan, a coal engineer who became a self-taught fossil expert after being sent to the remote village of Sanjiaocheng in China’s Liaoning province, Wang said. Pan donated the fossil to researchers.

Paleobotanists are wary of claims of the “oldest flower fossil” because the field was recently burned by an incorrectly dated fossil. In 2002, other scientists reported a 144 million year old man archefructus angiosperm fossil from China, which debuted on the cover of the journal Science, but the fossil was later dated at 124.6 million years old.

“This is our strongest evidence for Jurassic angiosperms that we have right now, but it’s tentative,” Taylor said of the new fossil. “If it was in the Cretaceous, no one would argue about it, but because it’s in the Jurassic, you need to have more evidence.”

rare find

Wang said Pan carefully documented his collections, and fossils and volcanic ash found in the same rock layers confirm the flower was buried during the Jurassic period. The fossil was named Euanthus panii; the first name is Latin for “true flower”, and the second name is in honor of Pan.

Euanthus panii, possibly the oldest flower fossil in the world. (Image credit: Liu & Wang, Historical Biology)

“I believe that as more and more fossils are documented from the Jurassic or earlier times, we will develop a new picture of angiosperm evolution that is completely different from the one we had in the past. last 100 years,” Wang said.

Wang and lead author Zhong-Jian Liu of the National Orchid Conservation Center of China published a description of the fossil online March 16 in the journal Historical Biology.

the E.panii the flower is tiny – just half an inch wide and tall (12 by 12.7 millimeters). But it has derived traits (recently appeared traits on the angiosperm family tree). There are male and female reproductive organs, such as sepals, anthers, and a stigma with a pollen-receptive surface, according to the study. Its separate petals are arranged like those of lilies or poppies. For botany enthusiasts, Wang said the flower has a unique feature of angiosperms: a four-part anther that contains pollen grains.

“You don’t need to know much about botany. You can recognize that it’s a flower,” Wang said.

But the details weren’t convincing to several scientists Live Science contacted about the study. For example, Patrick Herendeen, a plant evolutionary biologist and senior scientist at the Chicago Botanic Garden, said he believed the fossil was not a flower. “I’m completely unconvinced of their interpretations of the fossil,” Herendeen told Live Science in an email interview. “I don’t know what the fossil is, but I certainly don’t see what they’re bringing back.”

Editor’s note: This story was updated on April 9 to correct the first appearance of ferns in the fossil record, a reference to eudicots, and the description of the reproductive organs of flowers.

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