David A. Grimaldi of the American Museum of Natural History, who wrote the paper with Michael S. Engel of the University of Kansas, describes the find as "completely serendipitous." During the course of researching a book on insect evolution, he explains, they were initially focused on another sample stored in the vault of London¿s Natural History Museum. But the slide stored next to it¿a sample of chert (see top image) from Rhynie, Scotland, initially studied in 1928¿caught their interest, and they brought it back to the U.S. for further study. "I remember sticking it under my microscope," Grimaldi says, "and Michael and I kind of looked at each other and said, ¿Holy moly, do you see what I see? These are actual true insect mandibles [jaw parts].¿" Specifically, diagnostic features of the jaw's joint anatomy (see bottom image) indicate that the remains belonged to a winged insect, Rhyniognatha hirsti.
The oldest known evidence of winged insects¿that is, complete fossilized bodies with fully formed wings attached--dates to around 330 million years ago. But because there is a diversity of species capable of powered flight from this time period, insects clearly evolved wings well before that time. "This chert provides a tantalizing scrap of evidence to suggest that we¿re missing a huge amount," Grimaldi remarks, "and there¿s probably this wonderful progression of insects with protowings yet to be discovered."