Giant Roach Fossil Found in Ohio Coal Mine

Bijal P. Trivedi
National Geographic Today
November 12, 2001

Geologists at Ohio State University have discovered a fossil of a giant prehistoric cockroach that roamed North America about 300 million years ago.

The cockroach is about 3.5 inches long (9 centimeters)—twice as large as the average modern American roach but slightly smaller than some specimens found in the tropics.

The roach, which predates the dinosaurs by about 55 million years, scuttled around Ohio during the Carboniferous period when the state was hot and swampy.

Although bug fossils are quite common it is rare to find complete specimens. The Ohio specimen, which was found in a coal mine, was surprisingly well preserved.

The mine has also yielded a fossil of one of the smallest cockroaches, and another fossil has preserved the ancient color patterns of that insect.

"Normally, we can only hope to find fossils of shell and bones, because they have minerals in them that increase their chances for preservation," said Cary Easterday, a master's student at OSU. "But something unusual about the chemistry of this ancient site preserved organisms without shell or bones with incredible detail."

Intricate details of the giant cockroach have been preserved in the ancient rock. Scientists can see veins from the wings and fine bumps covering its surface. The antennae and legs are folded around its body, and even its mouth parts can be seen in the imprint.

The mine, located at the junction of Ohio State Routes 7 and 11, initially attracted attention because of the diverse range of plant fossils that were found there. What was most unusual was that many plant fossils found were three-dimensional, rather than the usual pressed 2-D fossils.

The strip coal mine has also yielded fossils of two rare arachnids, a giant centipede-like insect measuring about 60 inches long (150 centimeters) and 12 inches wide (30 centimeters), and a new genus and species of gerarid insect.

The Carboniferous was a period of dramatic climate change. At the time Easterday's cockroach was fossilized the climate was changing from a year-round wet tropical climate to seasonal tropical—with a wet and a dry season.

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