Recently, researchers discovered four ancient Ectobius species in the 49-million-year-old Green River Formation near Rifle, Colorado in deposits that are about five million years older than the Baltic amber.
However, these cockroaches soon became extinct in North America. The cause for the extinction of Ectobius in North America in the dim past is unknown, but it evidently survived in the Old World, and western Europe in particular.
Ectobius has a long fossil history in Europe, occurring in Baltic amber that is about 44 million years old, and its lineage was believed to have been exclusively from the Old World.
The new discovery has suggested that Ectobius may have originated in the New World.
"About 65 years ago, several entomologists in the northeastern United States noted that four species of Ectobius were present in North America," corresponding author Dr. Conrad Labandeira said.
"It was always assumed that these four newcomers were the first Ectobius species to have ever lived in North America. But the discovery in Colorado proves that their relatives were here nearly 50 million years ago," the researcher added.
The study is published in Annals of the Entomological Society of America.