Fossil dates winged insects back to 400 million years

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The identification of a 400-million-year-old insect pushes back the origins of Earth's most prolific life form by about 20 million years and ages the beginning of flight for all organisms, say two U.S. entomologists.

Discovered in Scotland during the 1920s, the fossilized creature -- a Rhyniognatha hirsti -- has been identified as the world's oldest known insect. It is estimated to be between 396 million and 407 million years old.

"This new fossil ... is the earliest documentable evidence of insect activity," said Michael S. Engel of the University of Kansas, who published with David A. Grimaldi, entomologist at the American Museum of Natural History in New York, the findings of their research in today's issue of the journal Nature.

The discovery pushes the origin of insects as far back as the Silurian era (420 million years ago), from which the earliest terrestrial ecosystems are known, Mr. Engel said.

An insect fossil found two decades ago in upstate New York was estimated to be 379 million year old, about 20 million years younger than the new finding.

"More primitive insects must be even older than this thing. ... Insects were probably among the earliest of all terrestrial animals," Mr. Engel said.

Although no wings were found, the triangular jaws are strikingly similar to those found only in winged insects, which previously were thought to have evolved about 320 million years ago.

Mr. Engel said this identification pushes the origin of flight for all organisms back 80 million years.

"The transition to flying animals took place significantly earlier than it was previously believed," he said.

Encased in translucent rock called chert, the fossil is as long as a grain of rice.

Australian entomologist Robin John Tillyard discovered the fossilized creature near Aberdeen and described it as a possible insect, but he did not draw a definitive conclusion.

Since then, the fossil has been housed at the Natural History Museum of London, without any scientist bothering to scrutinize it.

While researching for a book on insect evolution in 2002, Mr. Engel and Mr. Grimaldi visited the museum and examined the fossil with a special microscope that allowed them to see all the insect's true hallmarks.

The discovery, the entomologists said, should promote research about the mystery of the evolution of insects.