Fossil leaves may reveal climate in last era of dinosaurs

Embedded in the ancient rock is a triangular leaf with rounded upper lobes.

WASHINGTON (AP) — Richard Barclay opens a metal drawer in archives of the Smithsonian Natural History Museum containing fossils that are nearly 100 million years old. Despite their age, these rocks aren’t fragile. The geologist and botanist handles them with casual ease, placing one in his palm for closer examination.

Embedded in the ancient rock is a triangular leaf with rounded upper lobes. This leaf fell off a tree around the time that T-rex and triceratops roamed prehistoric forests, but the plant is instantly recognizable. “You can tell this is ginkgo, it’s a unique shape,” said Barclay. “It hasn’t changed much in many millions of years.”

What’s also special about ginkgo trees is that their fossils often preserve actual plant material, not simply a leaf’s impression. And that thin sheet of organic matter may be key to understanding the ancient climate system — and the possible future of our warming planet.

But Barclay and his team first need to crack the plant’s code to read information contained in the ancient leaf.

“Ginkgo is a pretty unique time capsule,” said Peter Crane, a Yale University paleobotanist. As he wrote in “Ginkgo,” his book on the plant, “It is hard to imagine that these trees, now towering above cars and commuters, grew up with the dinosaurs and have come down to us almost unchanged for 200 million years.”