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August 03, 2010
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Found: earliest known animal tracks?
Oct. 5, 2008
Courtesy Ohio State University
and World Science staff
Faint, fossilized
tracks of an ancient aquatic creature suggests animals walked using legs at least 30 million years earlier than had been thought, some scientists say. But they admit the lack of a fossil of the creature itself will probably foster a healthy skepticism, and that researchers will need to look for additional evidence. Researchers say this rock
displays tracks of one of the earliest animals—small, round dots in silt that later became
stone. (Photo by Kevin Fitzsimons, OSU)
The tracks—two parallel rows of small dots, each about two millimeters wide—are dated to some 570 million years ago, to a period called the Ediacaran. That preceded the Cambrian period, when most major groups of animals evolved.
Scientists once thought that mainly microbes and simple multicellular animals existed before the Cambrian, but that idea is changing, said Loren Babcock, professor of earth sciences at Ohio State University.
He pronounced himself “reasonably certain” a centipede-like arthropod or a legged worm made the tracks. An arthropod is an invertebrate having jointed limbs and a segmented body—a group that includes insects.
Soo-Yeun Ahn, a doctoral student at Ohio State and a co-author of the research, presented the findings at the Geological Society of America meeting Sunday in Houston.
Babcock said he found the tracks while surveying rocks in the mountains near Goldfield, Nevada in 2000. “We came on an outcrop that looked like it crossed the
Precambrian-Cambrian boundary.... We just sat down and started flipping rocks over. We were there less than an hour when I saw it.”
The creature must have stepped lightly onto the soft seabed, because its legs pressed only shallow pinpoints in it, Babcock said. But when he flipped over the rock bearing the little pits, the low-angle sunlight cast them in crisp shadow, he recalled. He couldn’t be sure of the creature’s length or number of legs, but he guessed it carried a centimeter-wide body on many spindly legs.
In 2002, other researchers reported a similar fossil trail from Canada that dated back to the middle of the Cambrian period, about 520 million years ago. Another set of tracks found in South China date back to 540 million years ago.
Babcock is an expert in the special chemical, physical and biological conditions that enabled some soft-bodied creatures to fossilize, a rare occurrence with them. He has found a menagerie of unusual fossils, from unusual echinoderms in Nevada to sulfur-eating bacteria in Antarctica.
The shallow sea over western Nevada 570 million years ago would have been good for preserving soft-bodied animals, Babcock said. The sediment surface was probably bound together by a microbial mat—a cohesive carpet of bacteria and sediment grains, which would readily preserve prints.
“I expect that there will be a lot of skepticism,” he said. “There should be. But I think it will cause some excitement. And it will probably cause some people to look harder at the rocks they already have. Sometimes it’s just a matter of thinking differently about the same specimen.”
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A newfound, fossilized trail of an aquatic creature suggests animals walked using legs at least 30 million years earlier than had been thought, some scientists say. But they admit the lack of a fossil of the creature itself will probably foster a healthy skepticism, and that researchers will need to look for additional evidence. The tracks—two parallel rows of small dots, each about two millimeters wide—are dated to some 570 million years ago, to a period called the Ediacaran. That preceded the Cambrian period, when most major groups of animals evolved. Scientists once thought that mainly microbes and simple multicellular animals existed before the Cambrian, but that idea is changing, said Loren Babcock, professor of earth sciences at Ohio State University. He pronounced himself “reasonably certain” a centipede-like arthropod or a legged worm made the tracks. An arthropod is an invertebrate having jointed limbs and a segmented body—a group that includes insects. Soo-Yeun Ahn, a doctoral student at Ohio State and a co-author of the research, presented the findings at the Geological Society of America meeting Sunday in Houston. Babcock said found the tracks while surveying rocks in the mountains near Goldfield, Nevada in 2000. “We came on an outcrop that looked like it crossed the Precambrian-Cambrian boundary.... We just sat down and started flipping rocks over. We were there less than an hour when I saw it.” The creature must have stepped lightly onto the soft seabed, because its legs pressed only shallow pinpoints in it, Babcock said. But when he flipped over the rock bearing the little pits, the low-angle sunlight cast them in crisp shadow, he recalled. He couldn’t be sure of the creature’s length or number of legs, but he guessed it carried a centimeter-wide body on many spindly legs. In 2002, other researchers reported a similar fossil trail from Canada that dated back to the middle of the Cambrian period, about 520 million years ago. Another set of tracks found in South China date back to 540 million years ago. Babcock is an expert in the special chemical, physical and biological conditions that enabled some soft-bodied creatures to fossilize, a rare occurrence with them. He has found a menagerie of unusual fossils, from unusual echinoderms in Nevada to sulfur-eating bacteria in Antarctica. The shallow sea over western Nevada 570 million years ago would have been good for preserving soft-bodied animals, Babcock said. The sediment surface was probably bound together by a microbial mat—a cohesive carpet of bacteria and sediment grains, which would readily preserve prints. “I expect that there will be a lot of skepticism,” he said. “There should be. But I think it will cause some excitement. And it will probably cause some people to look harder at the rocks they already have. Sometimes it’s just a matter of thinking differently about the same specimen.”