Fossil hunters in the United States have found the world's oldest known tree, a palm-like giant of a species called a Wattieza that lived some 380 million years ago.



Their discovery resolves a riddle that has dogged paleo-botanists for 137 years and sheds light on how forests slowly yet powerfully sculpted Earth's landscape, the team report in Nature, the weekly British science journal.

In June 2004, Linda VanAller Hernick and Frank Mannolini of the New York State Museum found the fossilised crown of a massive tree in a small sandstone quarry in New York that had already been a fruitful site for retrieving fossils of plants and arthropods.

Racing against the clock, for the quarry was about to be dug out to provide stone for road repair, the pair used an industrial saw, a pick-up truck and a manual engine hoist to extract the 200 kilogram specimen.

After gaining authorisation to continue collecting at the site, the following year they dug out a tree trunk of the same species, extracting it fragment by fragment and reassembling it like a eight-metre-long fossilised jigsaw puzzle.

The team describe the specimens in their paper as quite simply "spectacular".

Pieces of Wattieza have been found before, but the new find confirms its striking similarity to the modern tree fern.

It had a skinny palm-like trunk with, at its head, a spreading tuft of fronds, a system that cleverly conserved resources to help promote vertical growth so that the tree could pierce the forest canopy and get sunlight.

It had only a small root system, reproduced through spores, and probably reached around 10 metres in height when mature.

The Wattieza hails from the Middle Devonian period, from 397 to 385 million years ago, which was a critical time in the evolution of early land plants.

"The trees preceded the dinosaurs by 140 million years," palaeontologist Ed Landing, said.

"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.

"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," said fellow author Christopher Berry, a lecture in ancient botany at Cardiff University, Britain.

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 to 359 million years ago.

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," the museum quoted Ms Hernick as saying.

- AFP