About 315 million years ago, an insect landed on a muddy patch, sat for a while and flew off.

Amazingly, that bug’s muddy impression, about 1.5 inches long, hardened and survived to today.
“It left a perfect copy of its body,” said Richard J. Knecht, a curatorial assistant at the Museum of Comparative Zoology at Harvard, who uncovered the fossil in sandstone rocks in southeastern Massachusetts. “Essentially everything but the wings.”
Fragments of flying insects — usually just the wings — have been found dating to 325 million years ago. The Massachusetts fossil provides the earliest and perhaps best look at the body of an early flying insect. Mr. Knecht was searching for fossils near a swamp and found a promising rock outcrop.
The “first piece I picked was naturally split,” he recalled. “I opened it like a book and there was the fossil, both halves, a cast and mold.”
Mr. Knecht said that 315 million years ago, this place was near the side of a steep hill where sediment piled up quickly. Soon after the fly flew away, the impression was buried and preserved.
From the shape of the insect, Michael S. Engel, an entomologist at the University of Kansas, identified it as a mayfly, one of the first groups of flying insects. “It would look very similar to what’s around today,” Mr. Knecht said.
Mr. Knecht, Dr. Engel and Jacob S. Benner, a paleontologist at Tufts University, described the fossil impression in an article published in The Proceedings of the National Academy of Sciences.
(Source: The NYT)