Researchers found one of oldest known tree fossils in Gilboa, New York. The fossil is roughly 385 million years old and is one of the remains from the Genus Wattieza, a fern-like plant which formed Earth's first known forests.
Dr Berry described the discovery as a "spectacular" find.
The upright stumps of fossilised trees were first uncovered after a flash flood in Gilboa, New York, more than a century ago.
But until two further fossils were found two years ago, which had fallen sideways with their trunk, branches, twigs and crown still intact, no-one knew what the entire trees looked like.
The American team called in Dr Berry, who has 17 years of tree fossil expertise, to help.
Dr Berry, of Cardiff university's School of Earth, Ocean and Planetary Sciences, said it was a "spectacular find" which had allowed scientists to recreate early forest ecosystems.
"This was also a significant moment in the history of the planet," he said.