Discovery Sheds New Light on Plant Evolution

Posted September 23, 2002


FOR IMMEDIATE RELEASE - Monday, September 23, 2002 2002-09-18-AR

Discovery Sheds New Light on Plant Evolution

A University of Saskatchewan-led team has discovered 420-million-year-old
plant fossils in the Canadian North that radically alter the time scale of
plant evolution on Earth.

The discovery dates significant land vegetation development 10 million years
earlier than formerly assumed, says U of S geology chair James Basinger. The
American Journal of Botany published the team's findings in its June issue.

Fossils of the Silurian age are rare, but those found on Bathurst Island in
Nunavut, just 1,500 kilometers from the North Pole, are larger and more
developed than any other plant fossil from the same period.

"The Silurian fossils give evidence of an older, much more complex ecosystem
than we knew existed," said Basinger.

These plants are not the oldest ever discovered. Earlier vascular plants,
those with water-conducting tissue, stood only a fraction of an inch tall
and produced few sporangia (reproductive bodies). The Bathurst fossils
depict plants several inches tall with many branches and dense clusters of
sporangia that increase the plant's reproductive capacity.

"The timing of plant evolution is poorly understood because there's a meager
record of plants of that age," said Basinger. "Few fossils exist, as plants
were easily destroyed following death."

The Bathurst fossils are a record of when plants began adapting to land,
appearing in low, wet flora areas. After developing internal
water-conducting tissue, they moved onto land and lived in dry air rather
than water.

More than 200 million years before dinosaurs, these plants were swept into
the sea by swift running river-flow and buried in fine grain sand. They
were then preserved in marine sediment, along with invertebrates that
determine geological age and allow for accurate dating.

Basinger started collecting specimens in 1993 when evaluating the island for
fossil-finding potential. His team returned for four years even though
digging is impossible in permafrost and there is a limited window of
opportunity - only one month each year - when scientists can work in the
extremely harsh weather conditions.

"Bathurst Island is a special place to look for fossils because they are
well exposed in river beds," said Basinger. "It's a remote area and still
pristine because there has been little human presence to disturb the land
mass."

Of the five sites explored by the team, only one yielded the few dozen
specimens that change the chronology of plant development on Earth.

"These fossils are so rare that you could spend your life flipping rocks
looking for them," he says. "What we need to do is go back again in four or
five years after the climate has had a chance to weather and change the
landscape, exposing different rock. Then we might find more Silurian
fossils."

The team also discovered plants with roots, a significant find as there is
little information about when root systems first appeared or how they
evolved.

Team members include Michele Kotyk, a U of S graduate student who wrote her
Master's thesis and won the Toop Memorial Prize for Scientific Writing on
the Bathurst fossils, biologist Patricia Gensel from University of North
Carolina at Chapel Hill, and geologist Tim Freitas with Nexen Inc.

Research funding was provided by NSERC (Natural Sciences and Engineering
Research Council). The Polar Continental Shelf Project provided aircraft
use within the Arctic.

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For more information, contact:

Professor Jim Basinger
Head, Department of Geology
University of Saskatchewan
(306) 966-5684

Kathryn Warden
Research Communications
University of Saskatchewan
(306) 966-2506