Magazine article Science News

Fossil Find Stands on Its Own Four Legs. (into the Gap)

Magazine article Science News

Fossil Find Stands on Its Own Four Legs. (into the Gap)

Article excerpt

A fossil originally misidentified as an ancient fish turns out to be the nearly intact remains of a four-limbed creature, perhaps one of the first to walk on land. The find is particularly important because it dates from an era noted for its dearth of terrestrial fossils that illuminate the evolution of the ancestors of today's amphibians, reptiles, and mammals.

There's been plenty of fossil material for studying the evolution of some fish into early four-legged animals, or tetrapods. However, aquatic vertebrates with rudimentary legs disappear from the fossil record about 360 million years ago, says Jennifer A. Clack, a paleontologist at the University Museum of Zoology in Cambridge, England. Well-preserved tetrapod specimens don't turn up again until about 20 million years later, when many animals with modern-style limbs were strolling the planet.

That lengthy gap in the fossil record--nicknamed Romer's gap, after a scientist who searched in vain for fossils of terrestrial creatures from that time--coincides with the period when animals evolved efficient land walking.

"We know the animals were there," says Robert L. Carroll, a paleontologist at McGill University in Montreal. "We just don't know what they were like."

Enter Pederpes. Remains of the ancient creature were extracted from a lump of limestone discovered in Scotland in 1971. Impressions of fish scales and other fossils also embedded in the nodule had initially led scientists to consider the 65-centimeter assemblage of bones as an ancient fish that lived during Romer's gap. …

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