I won’t belabor this cool new paper on a fossil insect, for Ed Yong has already done over at Not Exactly Rocket Science. The paper is by Richard Knecht and colleagues, and is in the online edition of the Proceedings of the National Academy of Sciences. It describes the earliest known fossil of a flying insect—a fossil that is 310 million years old. Insects were the first animals to achieve powered flight, 90 million years before pterosaurs (“pterodactyls”).
It’s rare to find fossil insects, for their soft bodies rapidly decay before they can be buried and infiltrated with minerals. This fossil is in fact a trace fossil: not the mineralized body of the beast itself, but the filled-in impression that its body left in mud—mud that eventually became sandstone (click to enlarge). The insect almost certainly didn’t die from this contact, but simply touched down on the banks of a stream, left a body-shaped impression, and then took off again.
The authors identify this fossil, from southeastern Massachusetts, as a member of the stem group of mayflies (Ephemeroptera). Here’s a modern mayfly. Note that its head and wings are raised when it’s alighted.
The wings and head are not visible in the trace fossil (the insect probably raised them as it sat in the mud), so how do we know it flew? Three reasons. First, there are some traces in the stone that may be impressions of wings as they lightly touched the mud while beating. More important, the insect is clearly a mayfly, with all the body parts and appendages that testify to that lineage, and mayflies have wings. Finally, and most important, since it’s a trace fossil, had the insect walked to the spot where it laid down, it would have left “walking impressions” (i.e., footprints). There are none, suggesting that the beast touched down—that it landed after flying to the spot.
Knecht, R. J., M. S. Engel, and J. S. Benner. Late Carboniferous paleochnology reveals the oldest full-body impression of a flying insect. Proc. Nat. Acad. Sci., early edition.