World’s Oldest Fossil Forest Unearthed
Paleontologists have unearthed the extensive root system of 386-million-year-old (Devonian period) primitive trees in a sandstone quarry near Cairo, New York, the United States.
The Cairo fossil forest covered an area of at least 3,000 m2, and is one or two million years older than the Devonian fossil forest at Gilboa, also in New York and around 40 km away from the Cairo site.
“The Devonian period represents a time in which the first forest appeared on Earth,” said Binghamton University’s Professor William Stein.
“The effects were of first order magnitude, in terms of changes in ecosystems, what happens on the Earth’s surface and oceans, carbon dioxide concentration in the atmosphere, and global climate.”
“So many dramatic changes occurred at that time as a result of those original forests that basically, the world has never been the same since.”
Professor Stein and colleagues found that the Cairo forest was home to at least three unique root systems.
First, they identified a rooting system that they believe belonged to a palm tree-like plant called Eospermatopteris.
This tree, which was first discovered in the Gilboa forest, had relatively rudimentary roots. Like a weed, it likely occupied many environments, explaining its presence at both sites. But its roots had relatively limited range and probably lived only a year or two before dying and being replaced by other roots that would occupy the same space.
The paleontologists also found evidence of a tree species called Archaeopteris.
Although this tree behaved more like a fern during reproduction, by releasing spores into the air instead of forming seeds, it had early hints at what would one day become seed plants. Archaeopteris are the first known plants to form leaves, and were large woody plants formed from secondary tissues.
“Archaeopteris seems to reveal the beginning of the future of what forests will ultimately become,” Professor Stein said.
“Based on what we know from the body fossil evidence of Archaeopteris prior to this, and now from the rooting evidence that we’ve added at Cairo, these plants are very modern compared to other Devonian plants.”
The researchers found an extensive network of Archaeopteris roots which were more than 11 m in length in some places.
They also found a third root system belonging to a tree thought to only exist during the Carboniferous period and later: ‘scale trees’ belonging to the class Lycopsida.
The team believes that the Cairo forest was wiped out by a flood due to the presence of many fish fossils that were also visible on the surface of the quarry.
“It is surprising to see plants which were previously thought to have had mutually exclusive habitat preferences growing together on the ancient Catskill delta,” said Dr. Chris Berry, a scientist in the School of Earth and Ocean Sciences at Cardiff University.
“This would have looked like a fairly open forest with small to moderate sized coniferous-looking trees with individual and clumped tree-fern like plants of possibly smaller size growing between them.”
The discovery is reported in a paper in the journal Current Biology.
William E. Stein et al. Mid-Devonian Archaeopteris Roots Signal Revolutionary Change in Earliest Fossil Forests. Current Biology, published online December 19, 2019; doi: 10.1016/j.cub.2019.11.067