19 April 2007

Wattieza is world’s oldest tree

Cosmos Online
The first complete fossil of the world's oldest tree - a primitive 380-million-year-old plant resembling a modern palm or tree fern - has been uncovered by palaeontologists.
Wattieza is world's oldest tree

A reconstruction of how the crown portion of Wattieza would have looked in life. Credit: Frank Mannolini/New York State Museum

SYDNEY: The first complete fossil of the world’s oldest tree – a primitive 380-million-year-old plant resembling a modern palm or tree fern – has been uncovered by U.S. palaeontologists.

The eight-metre fossil of the species Wattieza has enabled scientists to reconstruct the ancient tree in its entirety for the first time, and solves a century-old palaeobotanical mystery. The species also lends new insights into the evolution of terrestrial trees and forest ecosystems.

“In forming the first forests, [these 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 binding the soil together,” said palaeobotanist Christopher Berry of Cardiff University in Wales.

Berry is part of the team that describes the find today in the British journal Nature.

In June 2004, palaeontologists Linda VanAller Hernick and Frank Mannolini of the New York State Museum in Albany, found the fossilised crown of a massive tree in a small sandstone quarry in Gilboa, New York. The site had already been a fruitful spot 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 pickup truck and a manual engine hoist to extract the hefty specimen.

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

Eschewing the traditional buttoned-down prose of scientific journals, the team describe the specimens in their paper as quite simply “spectacular.”

The find also solves a 137-year-old mystery. A “forest” of fossil stumps were discovered at a site just 16 km away in 1870, and had perplexed generations of botanists ever since. Without the upper sections of the trees, experts were unable to accurately identify the species.

“Now the riddle is solved,” with the discovery of a matching upper portion, said VanAller Hernick. “We know what was out there.”

Her team have traced the age of Wattieza species to the Devonian period (415 to 360 million years ago), an era in which the world’s primitive land plants first developed characteristics associated with modern-day trees – such as taller trunks, more diverse reproductive methods and the first signs of leaf development.

This was also the period when the first seed-bearing plants spread across dry land to form forests. Wattezia itself did not bear seeds and reproduced with spores, like today’s ferns.

Until the new discovery, the oldest known entire tree was Archaepoteris, a close relative of seed plants, which flourished in the late Devonian period. The Gilboa tree differs from this later species in having a smaller trunk, a more limited root system and in lacking horizontal branches and fully-developed leaves.

The discovery of a well-preserved Wattieza fossil provides scientists with vital insights into the structure and habits of early plants, commented botanists Brigitte Meyer-Berthaud and Anne-Laure Decombeix of the University of Montpellier in France. The pair, who were not involved in the discovery, are authors of an accompanying commentary in today’s Nature.

“Reconstructing entire fossil plants is an important step in assessing the patterns of plant diversification over time and the roles that plants played in past environments,” they wrote.

This is a particular challenge, they said, because plants naturally shed parts of their body throughout their lifetime. Complete reconstructions of trees are especially difficult, due to their intricate architecture and long lifespan.

with Agençe France-Presse

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