49-million-year-old cockroach fossils discovered in Colorado


Three years ago, Slovakian paleontologist Peter Vrsansky found a surprise in a shipment of fossils from Rifle, Colo. Hidden in the collection was an unexpected new peek into the insect world during the Eocene epoch, 50 million years ago. Vrsansky discovered four new species of Ectobius cockroach that are five million years older – and originated from a different continent – than scientists have long thought. It turns out that Ectobius cockroaches did not originate in the Old World – Europe and Africa – 44 million years ago, but in the New World – North America – 49 million years ago.

These insects were most likely scuttling around this continent, and apparently the mountains that predated the Rockies, before even acquainting themselves with Eurasia. Scientists say that the critters must have eventually migrated through either the then-balmy Arctic and into Scandadavia, or across the Bering Land Bridge and into Eurasia.

Uncovering specimens like these, “is like putting together a puzzle, but the pieces can be moved in space and time,” said Conrad Labandeira, a co-author of the scientific paper on the discovery and a senior scientist at the Smithsonian Museum in Washington, DC.Every time you put a piece in its place, you flesh out these patterns of evolution.”

Ectobius kholsi fossils found in the Green River Formation in western Colorado. It was recently discovered that these insects lived in what is now North America, 49 million years ago.

The man who actually unearthed the cockroach specimens is David Kohls, an avid fossil hunter from Battlement Mesa, Colo. The amateur collector uncovered the fossils from bluffs overlooking the Colorado River in Garfield County, Colo. It was one of countless trips he made to the Green River Formation, and he was probably armed with a rock hammer, a wood chisel, and plenty of newspaper to wrap any delicate findings. At the time, over a decade ago, he didn’t realize the implications of his find. “But evidently it was a pretty big deal,” he said this week.

The Green River Formation, part of which is close to Kohl’s home, is a particularly good place to hunt for fossils; large, shallow lakes that once covered the area preserved a rich library of plants and animals. Plus, the formation is young enough that it escaped some long-term geological processes like erosion and metamorphism that can ruin the quality of fossils.