Found! World's oldest tree
Fossil hunters say they have found the world's oldest known tree, a palm-like giant that lived some 380 million years ago.
The tree, called a Wattieza, would have lived millions of years before the dinosaurs and Australia's Wollemi pine.
The discovery resolves a riddle that has dogged palaeobotanists for 137 years and sheds light on how forests slowly yet powerfully sculpted Earth's landscape, the team reports today in the journal Nature.
Scientists believe these early forests absorbed carbon dioxide, cooling the Earth's surface.
Wattieza was like a modern tree fern, the researchers say.
It had a skinny palm-like trunk with a spreading tuft of fronds at its head. This arrangement cleverly conserves resources to help promote vertical growth so that the tree can pierce the forest canopy and get sunlight.
It had only a small root system, reproduced through spores, and probably reached around 10 metres high when mature.
The Wattieza hails from the Middle Devonian period, 397-385 million years ago, which was a critical time in the evolution of early land plants.
The Middle Devonian was an incubator era, giving rise to a whole range of reproductive strategies among plants and the precursors of leaves for photosynthesis.
When these specimens of Wattieza were alive, terrestrial life in that area was limited to small arthropods, a class of animals that includes insects, spiders and crustaceans.
"The trees preceded the dinosaurs by 140 million years," says co-author and palaeontologist Dr Ed Landing, from the New York State Museum.
"There was nothing flying, no reptiles and no amphibians."
The fossils provide the first solid evidence about the overall shape and size of early trees and could help explain how forests came to dominate the land surface, a feature that is visible even today.
"In forming the first forests, [trees] must have really changed the Earth system as a whole, creating new types of micro-environments for smaller plants and insects, storing large amounts of carbon and bringing the soil together," says fellow author Dr Christopher Berry, a lecture in ancient botany at Cardiff University.
Until now, the record for arboreal antiquity had been held by a specimen of Archaeopteris, a close relative of seed plants that flourished during the Late Devonian period, around 385-359 million years ago.
Archaeopteris was a very different beast from Wattieza. It was conifer-like, had leafy twigs, a large root systems and long-lived branches that grew from the side of the trunk.
The quarry where Wattieza was found is just 16 kilometres from Gilboa, a name that has special resonance for botanists.
There, in 1870, workers were blasting for rock to repair roads damaged by a flood when they came across fossil tree stumps.
These stumps have been widely cited as being evidence of Earth's oldest forest, but they always defeated attempts to find out more, as the important upper portions of the trees were missing.
"Now the riddle is solved and we know what was out there," says author Linda VanAller Hernick of the New York State Museum.