Tetrapods trod on land earlier than believed
Source: Agencies |
January 8, 2010, Friday
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THE water-dwelling ancestors of modern-day mammals, reptiles and birds emerged onto land millions of years earlier than previously believed, researchers reported in Britain.
A set of fossilized footprints show that the first tetrapods - a term applied to any four-footed animal with a spine - were treading open ground 397 million years ago, well before scientists thought they existed.
An expert unconnected with the research said the find would force experts to reconsider a critical period in evolution when sea-based vertebrates took their first steps toward becoming dinosaurs, mammals and - eventually - human beings.
"It blows the whole story out of the water, so to speak," said Jenny Clack, a paleontologist at Cambridge University.
The work appeared in yesterday's issue of the journal Nature.
Until now, scientists thought they had the evolution from fin to foot fairly well understood. The earliest tetrapods had been traced to 385 million years ago. Experts theorized that they had split from their close relatives, a fleshy-finned family of fish, a few million years earlier and then gone on to conquer land.
But the new fossil footprints - uncovered between 2002 and 2007 in a disused quarry in Poland - push the timing back several million years, according to Grzegorz Pienkowski, the scientific director of the Polish Geological Institute in Warsaw, where most of the article's authors are based. He said the fossils had been securely dated.
Although at least some of the footprints may have been made in shallow water, paleontologist Per Ahlberg, one of the article's co-authors, said it was nevertheless clear from the shape of the toe prints and the nature of the sediment that the animals spent time walking around on land.
Although she acknowledged their importance, Clack warned against drawing conclusions exclusively on small marks left by animals on the bottom of a muddy surface hundreds of millions of years ago. She said it would be critical to see fossil evidence of the creature that made the footprints.
A set of fossilized footprints show that the first tetrapods - a term applied to any four-footed animal with a spine - were treading open ground 397 million years ago, well before scientists thought they existed.
An expert unconnected with the research said the find would force experts to reconsider a critical period in evolution when sea-based vertebrates took their first steps toward becoming dinosaurs, mammals and - eventually - human beings.
"It blows the whole story out of the water, so to speak," said Jenny Clack, a paleontologist at Cambridge University.
The work appeared in yesterday's issue of the journal Nature.
Until now, scientists thought they had the evolution from fin to foot fairly well understood. The earliest tetrapods had been traced to 385 million years ago. Experts theorized that they had split from their close relatives, a fleshy-finned family of fish, a few million years earlier and then gone on to conquer land.
But the new fossil footprints - uncovered between 2002 and 2007 in a disused quarry in Poland - push the timing back several million years, according to Grzegorz Pienkowski, the scientific director of the Polish Geological Institute in Warsaw, where most of the article's authors are based. He said the fossils had been securely dated.
Although at least some of the footprints may have been made in shallow water, paleontologist Per Ahlberg, one of the article's co-authors, said it was nevertheless clear from the shape of the toe prints and the nature of the sediment that the animals spent time walking around on land.
Although she acknowledged their importance, Clack warned against drawing conclusions exclusively on small marks left by animals on the bottom of a muddy surface hundreds of millions of years ago. She said it would be critical to see fossil evidence of the creature that made the footprints.
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