BOSTON -- Geologists at Ohio State University have found the largest-ever complete fossil of a cockroach, one that lived 55 million years before the first dinosaurs.
The cockroach, along with hundreds of other fossil plants and animals from a coalmine in eastern Ohio, could help scientists better understand the diversity of ancient life and how the Earth's climate has changed throughout history.
The roach lived 300 million years ago, during what geologists call the Carboniferous period, explained Cary Easterday, a master's student in geological sciences at Ohio State. Ohio was a giant tropical swamp then, but this particular site was unusual.
"Normally, we can only hope to find fossils of shell and bones, because they have minerals in them that increase their chances for preservation," Easterday said, "but something unusual about the chemistry of this ancient site preserved organisms without shell or bones with incredible detail."
Easterday presented his findings November 7 at the annual meeting of the Geological Society of America in Boston.
Among features visible in the 3.5-inch long cockroach are veins in the insect's wings, and fine bumps covering the wing surface. The roach's legs and antennae, folded around its body, are also evident, as well as mouth parts.
Loren Babcock, associate professor of geological sciences and Easterday's advisor, said scientists have only incomplete answers about what caused such extraordinary details to be preserved at the site.
Easterday said the mine first caught scientists' attention because of the plants that were preserved there, including the earliest known conifer in the Appalachian Basin.
He obtained the cockroach and other fossils in 1999 with the assistance of Gregory McComas, an avid fossil collector and geology graduate of Youngstown State University in Ohio. McComas discovered the fossil site in 1979, and named it the "7-11 Mine" because it is located at the intersection of Ohio State Routes 7 and 11.
When Easterday compared the fossil cockroach from the 7-11 Mine to cockroaches living in the tropics today, he found them similar. Though the fossil cockroach is about twice as big as the average American roach, some modern roaches in the tropics are known to grow to four inches or bigger.
Since the fossil plants and animals lived at a time when a drought was rapidly drying out their ancient swamp, Babcock and Easterday hope further study of the 7-11 site will reveal how these organisms coped with their changing environment.
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