mIEKAL aND
2007-04-23 14:33:53 UTC
Prehistoric Mystery Organism Verified as Giant Fungus
By: University of Chicago
Published: Apr 23, 2007 at 06:46
Scientists at the University of Chicago and the National Museum of
Natural History in Washington, D.C., have produced new evidence to
finally resolve the mysterious identity of what they regard as one of
the weirdest organisms that ever lived.
Their chemical analysis indicates that the organism was a fungus, the
scientists report in the May issue of the journal of Geology,
published by the Geological Society of America. Called Prototaxites
(pronounced pro-toe-tax-eye-tees), the organism went extinct
approximately 350 million years ago.
Prototaxites has generated controversy for more than a century.
Originally classified as a conifer, scientists later argued that it
was instead a lichen, various types of algae or a fungus. Whatever it
was, it stood in tree-like trunks more than 20 feet tall, making it
the largest-known organism on land in its day.
"No matter what argument you put forth, people say, well, that's
crazy. That doesn't make any sense," said C. Kevin Boyce, an
Assistant Professor in Geophysical Sciences at Chicago. "A 20-foot-
tall fungus doesn't make any sense. Neither does a 20-foot-tall algae
make any sense, but here's the fossil."
The Geology paper adds a new line of evidence indicating that the
organism is a fungus. The fungus classification first emerged in
1919, with Francis Hueber of the National Museum of Natural History
in Washington, D.C., reviving the idea in 2001. His detailed studies
of internal structure have provided the strongest anatomical evidence
that Prototaxites is not a plant, but a fungus.
"Fran Hueber has contributed more to our understanding of
Prototaxites than anyone else, living or dead," said Carol Hotton,
also of the National Museum of Natural History. "He built up a
convincing case based on the internal structure of the beast that it
was a giant fungus, but agonized over the fact that he was never able
to find a smoking gun in the form of reproductive structures that
would convince the world that it was indeed a fungus," Hotton said.
Co-authoring the Geology paper with Boyce, Hotton and Hueber himself
were Marilyn Fogel, George Cody and Robert Hazen of the Carnegie
Institution of Washington, and Andrew Knoll of Harvard University.
Their work was funded by NASA's Astrobiology Institute and by the
American Chemical Society Petroleum Fund.
Prototaxites lived worldwide from approximately 420 million to 350
million years ago. During this period, which spans part of the
Silurian and Devonian periods of geologic time, terrestrial Earth
looked quite alien in comparison to the modern world.
Simple vascular plants, the ancestors of the familiar conifers, ferns
and flowering plants of today, began to diversify on land during the
Devonian Period. "Initially, they're just stems. They don't have
roots. They don't have leaves. They don't have anything like that,"
Boyce said.
Millipedes, wingless insects and worms were among the other organisms
making a living on land by then, but no backboned animals had yet
evolved out of the oceans. "That world was a very strange place,"
Boyce said.
Although vascular plants had established themselves on land 40
million years before the appearance of Prototaxites, the tallest
among them stood no more than a couple feet high. By the end of the
Devonian, approximately 345 million years ago, large trees, ferns,
seeds, leaves and roots had all evolved. "They're all there. They
just exploded over this one time period," Boyce said.
Canadian paleontologist Charles Dawson published the first research
on Prototaxites in 1859, based on specimens found along the shores of
Gaspé Bay in Quebec, Canada. Hueber pored through Dawson's field
notebooks, written "in a completely illegible scrawl," Hotton said.
"Fran spent months deciphering them for clues about the localities
where specimens had been collected, how Dawson interpreted them and
other information that helped understand this humongous fungus," she
said.
Hueber also traveled to Canada, Australia and Saudi Arabia to collect
specimens. He tediously sliced them into hundreds of thin sections
and made thousands of images taken through microscopes to determine
the organism's identity.
Now Boyce, Hotton and their colleagues have produced independent
evidence that supports Hueber's case. The team did so by analyzing
two varieties-isotopes-of carbon contained in Prototaxites and the
plants that lived in the same environment approximately 400 million
years ago.
The metabolism of plants is limited by photosynthesis. Deriving their
energy from the sun and their carbon from carbon dioxide in the air,
any given type of plant will typically contain a similar ratio of
carbon-12 to carbon-13 as another plant of the same type. "But if
you're an animal, you will look like whatever you eat," Boyce said.
And Prototaxites displayed a much wider variation in its ratio of
carbon-12 to carbon-13 content than would be expected in any plant.
Geological processes can alter the isotopic composition of fossils,
but Boyce and his colleagues conducted tests to verify that the
carbon isotopic composition of the specimens they analyzed stemmed
from organic rather than geologic factors.
As for why these bizarre organisms grew so large, "I've wondered
whether it enabled Prototaxites to distribute its spores widely,
allowing it to occupy suitable marshy habitats that may have been
patchily distributed on the landscape," Hotton said.
The relatively simple Devonian ecosystems certainly seemed to contain
nothing to prevent them from growing slowly for a long time. Plant-
eating animals had not yet evolved, Boyce said. But even if
Prototaxites hadn't been eaten by the dinosaurs and elephants that
came much later, they probably grew too slowly to rebuild from
regular disturbances of any kind, Boyce said.
"It's hard to imagine these things surviving in the modern world," he
said.
By: University of Chicago
Published: Apr 23, 2007 at 06:46
Scientists at the University of Chicago and the National Museum of
Natural History in Washington, D.C., have produced new evidence to
finally resolve the mysterious identity of what they regard as one of
the weirdest organisms that ever lived.
Their chemical analysis indicates that the organism was a fungus, the
scientists report in the May issue of the journal of Geology,
published by the Geological Society of America. Called Prototaxites
(pronounced pro-toe-tax-eye-tees), the organism went extinct
approximately 350 million years ago.
Prototaxites has generated controversy for more than a century.
Originally classified as a conifer, scientists later argued that it
was instead a lichen, various types of algae or a fungus. Whatever it
was, it stood in tree-like trunks more than 20 feet tall, making it
the largest-known organism on land in its day.
"No matter what argument you put forth, people say, well, that's
crazy. That doesn't make any sense," said C. Kevin Boyce, an
Assistant Professor in Geophysical Sciences at Chicago. "A 20-foot-
tall fungus doesn't make any sense. Neither does a 20-foot-tall algae
make any sense, but here's the fossil."
The Geology paper adds a new line of evidence indicating that the
organism is a fungus. The fungus classification first emerged in
1919, with Francis Hueber of the National Museum of Natural History
in Washington, D.C., reviving the idea in 2001. His detailed studies
of internal structure have provided the strongest anatomical evidence
that Prototaxites is not a plant, but a fungus.
"Fran Hueber has contributed more to our understanding of
Prototaxites than anyone else, living or dead," said Carol Hotton,
also of the National Museum of Natural History. "He built up a
convincing case based on the internal structure of the beast that it
was a giant fungus, but agonized over the fact that he was never able
to find a smoking gun in the form of reproductive structures that
would convince the world that it was indeed a fungus," Hotton said.
Co-authoring the Geology paper with Boyce, Hotton and Hueber himself
were Marilyn Fogel, George Cody and Robert Hazen of the Carnegie
Institution of Washington, and Andrew Knoll of Harvard University.
Their work was funded by NASA's Astrobiology Institute and by the
American Chemical Society Petroleum Fund.
Prototaxites lived worldwide from approximately 420 million to 350
million years ago. During this period, which spans part of the
Silurian and Devonian periods of geologic time, terrestrial Earth
looked quite alien in comparison to the modern world.
Simple vascular plants, the ancestors of the familiar conifers, ferns
and flowering plants of today, began to diversify on land during the
Devonian Period. "Initially, they're just stems. They don't have
roots. They don't have leaves. They don't have anything like that,"
Boyce said.
Millipedes, wingless insects and worms were among the other organisms
making a living on land by then, but no backboned animals had yet
evolved out of the oceans. "That world was a very strange place,"
Boyce said.
Although vascular plants had established themselves on land 40
million years before the appearance of Prototaxites, the tallest
among them stood no more than a couple feet high. By the end of the
Devonian, approximately 345 million years ago, large trees, ferns,
seeds, leaves and roots had all evolved. "They're all there. They
just exploded over this one time period," Boyce said.
Canadian paleontologist Charles Dawson published the first research
on Prototaxites in 1859, based on specimens found along the shores of
Gaspé Bay in Quebec, Canada. Hueber pored through Dawson's field
notebooks, written "in a completely illegible scrawl," Hotton said.
"Fran spent months deciphering them for clues about the localities
where specimens had been collected, how Dawson interpreted them and
other information that helped understand this humongous fungus," she
said.
Hueber also traveled to Canada, Australia and Saudi Arabia to collect
specimens. He tediously sliced them into hundreds of thin sections
and made thousands of images taken through microscopes to determine
the organism's identity.
Now Boyce, Hotton and their colleagues have produced independent
evidence that supports Hueber's case. The team did so by analyzing
two varieties-isotopes-of carbon contained in Prototaxites and the
plants that lived in the same environment approximately 400 million
years ago.
The metabolism of plants is limited by photosynthesis. Deriving their
energy from the sun and their carbon from carbon dioxide in the air,
any given type of plant will typically contain a similar ratio of
carbon-12 to carbon-13 as another plant of the same type. "But if
you're an animal, you will look like whatever you eat," Boyce said.
And Prototaxites displayed a much wider variation in its ratio of
carbon-12 to carbon-13 content than would be expected in any plant.
Geological processes can alter the isotopic composition of fossils,
but Boyce and his colleagues conducted tests to verify that the
carbon isotopic composition of the specimens they analyzed stemmed
from organic rather than geologic factors.
As for why these bizarre organisms grew so large, "I've wondered
whether it enabled Prototaxites to distribute its spores widely,
allowing it to occupy suitable marshy habitats that may have been
patchily distributed on the landscape," Hotton said.
The relatively simple Devonian ecosystems certainly seemed to contain
nothing to prevent them from growing slowly for a long time. Plant-
eating animals had not yet evolved, Boyce said. But even if
Prototaxites hadn't been eaten by the dinosaurs and elephants that
came much later, they probably grew too slowly to rebuild from
regular disturbances of any kind, Boyce said.
"It's hard to imagine these things surviving in the modern world," he
said.