315 million-year-old mayfly

From the April 4 New York Times, an awesome image of a 315 million-year-old mayfly trace fossil.

This sandstone is from the time period known as the late Carboniferous (Pennsylvanian Period).  One fine day, a mayfly-like insect landed here in the mud, sat for a few seconds, and then took off again,  Improbably, the impression was preserved through hundreds of millions of years of geologic time only seeing the light of day when Richard Knecht, a curatorial assistant at the Museum of Comparative Zoology at Harvard, picked up and split open the rock while looking for fossils in a swamp near North Attleboro, Massachusetts.

The fossil is from the Wamsutta Formation which outcrops in the northwestern corner of the Narragansett Basin which itself extends from Rhode Island into southweastern Massachusetts. The rocks consist of 300 meters of red sandstones and shales interbedded with conglomerates that were deposited mainly in stream channels and floodplains.

The authors of the paper on this find describe the paleogeographic setting of the Wamsutta here as "representing deposition on tropical-latitude, low-relief, wet, and possibly forested alluvial fans."

It's a neat snapshot into life tens of millions of years before the first appearance of dinosaurs on Earth.

Here's the abstract for the soon to appear in print discussion of this fossil in the Proceedings of the National Academy of Sciences.