A Flowering Plant, Set in Stone

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Smithsonian readers may recognize the Liaoning province of China as the place where amazing fossils of bird-like dinosaurs have been found:

In a pine forest in rural northeastern China, a rugged shale slope is packed with the remains of extinct creatures from 125 million years ago, when this part of Liaoning province was covered with freshwater lakes. Volcanic eruptions regularly convulsed the area at the time, entombing untold millions of reptiles, fish, snails and insects in ash. I step gingerly among the myriad fossils, pick up a shale slab not much larger than my hand and smack its edge with a rock hammer. A seam splits a russet-colored fish in half, producing mirror impressions of delicate fins and bones as thin as human hairs.

One of China's star paleontologists, Zhou Zhonghe, smiles. "Amazing place, isn't it?" he says.

One of the latest finds from this province is this 125-million-year-old fossil of a flowering plant, Leefructus mirus, the earliest intact fossil of a eudicot, a familiar group of plants that includes modern maple trees and dandelions. It's easy to see, almost as if someone had outlined it all in marker, the plant's single stem, five leaves and a flower nestled in the middle. The plant is 6.3 inches tall and the fossil is so clear that even the flower petals are apparent. Most information about the evolution of plants during this time comes from fossilized pollen, which makes this discovery even more special.

"This fossil opens up a new way of thinking about the evolution of the first flowering plants," said Indiana University biologist David Dilcher, one of the co-authors of the Nature paper describing the find. "We are also beginning to understand that the explosive radiation of all flowering plants about 111 million years ago has had a long history that began with the slower diversification of many families of eudicots over 10, perhaps 15 million years earlier."

Once flowering plants evolved, they came to dominate our landscape. Evolutionary biologists are interested in how that happened, especially since it led to the diversification of other non-plant species, including pollinators and seed-eaters.

When Leefructus was alive, bees hadn't yet evolved, but scientists think that flies, beetles or other pollinators could have taken up that role for this flower. "Leefructus was found in the volcanic ash beds of an ancient lake," Dilcher said. "I think it was living near a lake, perhaps in a wet or marshy area much as buttercups do today."

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