Several years ago my daughter and I took a minivacation to Kelleys Island, home of the famous Glacial Grooves. While we were there the island experienced an explosion of mayflies – they were everywhere. A recent report from a famous fossil site in Brazil indicates they’ve been doing that for a long time.
The mayfly fossils were found in the Crato Formation, which formed in large lakes in what is now northeastern Brazil during the Cretaceous Period, the last period of the non-avian dinosaurs. The lakes may have been 30 miles wide and 60 miles long.
The Crato Formation is an example of what is known as a lagerstatte, a site that has a lot of fossils or fossils that are preserved exceptionally well, sometimes (but rarely) both. Another lagerstatte you might have heard of is the Burgess Shale, a 500-million-year-old Middle Cambrian site in the Canadian Rockies of British Columbia. Another is the 150-million-year-old Solnhofen Limestone of the Jurassic Period from the Bavarian region of Germany, source of the only known specimens of Archaeopteryx, the first bird.