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Oldest complex organic molecules found in fossils
Oct. 25, 2006
By Pam Frost Gorder/Ohio State University
and World Science staff
Geologists say they’ve found complex organic
molecules, characteristic components of living things, in 350-million-year-old fossil sea creatures—the
oldest such molecules yet found. These offer a new way to map evolution, the researchers said. A modern crinoid, also
known as a sea lily. (Courtesy
NOAA) Fossils of
crinoids from 350 million years ago.
(Courtesy OSU)
The molecules, they added, are ones that today serve as orange and yellow pigments in related animals,
and thus might have
done the same back then.
Christina O’Malley, a doctoral student in earth sciences at Ohio State University in Columbus, Ohio,
reported finding the bunches of atoms in fossils of several species of sea creatures called crinoids.
She reported the research Wednesday at the meeting of the Geological Society of America in
Philadelphia.
Crinoids, also known as sea lilies, still exist. They resemble plants, but are animals. They cling to the
seafloor and eat plankton, masses of tiny plant and animal organisms
that drift by.
The crinoids in this study had flower-like fronds capping skinny stalks about six inches (15 cm) high—a look resembling “starfish on a stick,” said William Ausich, an earth sciences professor and O’Malley’s co-advisor at Ohio State.
Crinoids today display varied colors, including shades of red, orange, and yellow, so it
would make sense that similar colors
turned up in their forebears, Ausich said.
It’s not the first time that ancient organic molecules from fossils
have been reported, O’Malley said. But to her knowledge, she added,
these are the oldest, and also the first that can be linked to individual
species.
Because the molecules seem to be slightly different for each crinoid species, scientists can use
them as markers to map relationships on the creatures’ family tree, the researchers said. Until now, they could only infer crinoid
lineage based on the size and shape of key
skeletal features.
“We can look for clues about these creatures’ lives in a way that hasn’t been attempted,” O’Malley said.
Scientists can normally view fossilized plants and animals only in the grays and tans of
sedimentary rock, such as the limestone fossils in this study. Rock
normally replaces organic molecules during fossilization.
But “crinoid skeleton is very porous,” she said, so apparently
some organic molecules were trapped in it and survived fossilization.
O’Malley said she found pigments in every crinoid specimen sampled from three fossil sites, one in Switzerland and two in Indiana.
The Indiana samples date back 350 million years, the scientists said,
to the so-called Mississippian period, when much of North America was under a shallow inland sea. The Switzerland fossils were dated
to 60 million years ago, the Jurassic period. The sites preserved the crinoids exceptionally well, they added, probably because a sudden storm buried them in sediment.
Should pigments be found in other fossils, the technique could prove a reliable way to trace species’ evolution, the researchers continued. So far, the crinoid “biomarkers” mesh well with
current concepts of how those species are related, they said.
Organic molecules might also survive in fossils
of other types of animals, but it’s
not clear whether it would be as easy to extract them, nor whether the same methods would
be suitable,
O’Malley said. “Very few studies have looked for complex organic molecules in fossils,”
she wrote in an email.
O’Malley isolated molecules by grinding up and dissolving
tiny bits of fossil, then injecting some of the resulting solution into a machine called a gas chromatograph mass spectrometer. This vaporized the solution so that a magnet could separate
molecules by electric charge and mass. Computer software then identified them.
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Geologists say they have found the oldest complex organic molecules, characteristic components of living things, in 350-million-year-old fossil sea creatures. The ancient molecules contain information that offers a totally new way map evolution, the researchers said. The molecules in this case, they added, are ones that today function as orange and yellow pigments in related animals, so they might have served the same purpose back then. Christina O’Malley, a doctoral student in earth sciences at Ohio State University in Columbus, Ohio, found the molecules in fossils of several species of sea creatures known as crinoids. She reported the research Wednesday at the meeting of the Geological Society of America in Philadelphia. Crinoids still exist. They resemble plants, but are animals. They cling to the seafloor and eat plankton, masses of tiny plant and animal organisms, drifting by. The crinoids in this study had flower-like fronds capping skinny stalks about six inches (15 cm) high—a look resembling “starfish on a stick,” said William Ausich, an earth sciences professor and O’Malley’s co-advisor at Ohio State. Crinoids today display varied colors, including shades of red, orange, and yellow, so it makes sense that similar turned up in their forebears, Ausich said. “People have suspected for a long time that organic molecules could be found inside fossils,” he added. “This is just the first time that scientists have succeeded in finding them.” Because the molecules seem to be slightly different for each crinoid species, scientists can now use the pigments as markers to map relationships on the creatures’ family tree, the researchers said. Until now, they could only infer crinoid lineage based on the size and shape of key features on the animals’ skeletons. “We can look for clues about these creature’s lives in a way that hasn’t been attempted,” O’Malley said. Scientists can normally view fossilized plants and animals only in the grays and tans of sedimentary rock, such as the limestone fossils in this study. Rock is inorganic, and replaces organic molecules during fossilization. What O’Malley and her colleagues found is that some organic molecules occasionally survive. “Crinoid skeleton is very porous,” she said. “We think that when inorganic molecules filled in the spaces of the skeleton during preservation, some of the organic molecules were trapped inside the fossil.” O’Malley said she found pigments in every crinoid specimen sampled from three fossil sites, one in Switzerland and two in Indiana. The Indiana samples date back to 350 million years ago, the scientists said, during the so-called Mississippian period, when much of North America was under a shallow inland sea. The Switzerland fossils were dated back 60 million years, to the Jurassic period. The sites preserved the crinoids exceptionally well, they added, probably because a sudden storm buried them in sediment. Should pigments be found in other fossils, the technique could prove a reliable way to trace species’ evolution, the researchers continued. So far, the crinoid “biomarkers” mesh well with scientists’ concepts of how those species are related, they said. O’Malley isolated pigments by grinding up bits of fossil, dissolving the organic molecules and injecting a sample of the resulting solution into a machine called a gas chromatograph mass spectrometer. This vaporized the solution so that a magnet could separate molecules by their electric charge and mass. Computer software then identified them.