A Xinicaulis tree trunk fossilPNASDuring the Devonian period, from about 420 million to 359 million years ago, complex terrestrial plant life really took off. The first rooted plants evolved, and by the end of the period, forests had colonized the environment, sucking up vast amounts of carbon, driving down global temperatures, and creating an entirely new kind of ecosystem.
Fossils of those first trees, cladoxylopsids, can still be seen in places such as Gilboa in the Catskill Mountains of upstate New York, where stumps up to 2 meters in diameter beckon visitors to imagine what the Earth might have looked like back before the dinosaurs. Even for paleobotanists, the arboreal remains—and cladoxylopsid remnants from other sites—left a lot to the imagination.
Cladoxylopsid remnants at the Gilboa fossil forest in New York StateFLICKR/DOUG KERRResearchers could tell that the trees had lacked wood, but what they couldn’t discern, says Chris Berry, a paleobotanist at Cardiff University in the U.K., was how woodless trees had managed to support such size. He and William Stein, a paleobotanist at Binghamton University in New York, “spent 10 years trying to work it out, sawing up bits of these big sandy stumps from Gilboa, and we got absolutely nowhere,” he says.
Then, in 2012, Hong-He Xu, a former postdoc of Berry now at the Nanjing Institute of Geology and Paleontology, unearthed a 15-centimeter cladoxylopsid stump in China’s northwest corner, not far from the Kazakhstan border. The fossil’s structures had ...
