October 17, 2008—Fossil hunters searching woods behind a suburban shopping mall have scored a basement bargain: a piece of rock with the oldest known impression of a flying insect (above).

The 300-million-year old specimen—from the Carboniferous period—is an extremely rare find, according to the Tufts University team.

That's because bodies of flying insects are usually not preserved due to their softer, fragile nature, said Richard J. Knecht, who made the discovery with colleague Jake Benner.

Scientists more often find the remains of wings, which are not digested easily by predators, Knecht told National Geographic News.

(Read about the oldest bee found trapped in amber.)

The 3-inch (7.6-centimeter) insect—which resembles a modern mayfly—likely stayed in the mud long enough to move its leg before flying off, leaving a perfect impression. "It really is like winning the lottery," Knecht said.

The team found the fossil in a rock outcrop in North Attleboro, Massachusetts.

They had decided to scout out a fossil-rich area mentioned in a long-forgotten 1929 masters thesis by a Brown University student—an area that's now sure to yield more fossils, Knecht said.

Benner and Knecht presented their find in September at the Second International Congress on Ichnology—the study of fossilized animal tracks—in Kraków, Poland.

—Christine Dell'Amore