A fossil identified by a University of Nebraska-Lincoln entomologist as the world's largest known scarab beetle fossil represents a new genus and species.

Oryctoantiquus borealis was named in June by Brett C. Ratcliffe, curator of insects at the University of Nebraska State Museum and professor of entomology, and Dena Smith, a geologist at the University of Colorado.

Their article describing the fossil beetle was published in Coleopterists Bulletin, a scientific journal devoted to the study of beetles. The fossil is a ventral mold of a jumbled portion of the beetle's sternum and some of its legs.

The fossil was found in north-central Oregon in the 45-million-year-old Middle Eocene Clarno Formation by Smith and a paleontologist from the University of California-Berkeley.

Smith was referred to Ratcliffe, who had worked with paleontologists to identify fossils of insect remains and who leads an internationally recognized lab that specializes in the taxonomy of scarab beetles.

"This specimen is also the oldest specimen attributable to a group of scarabs known as rhinoceros beetles," Ratcliffe said in a news release. "Rhinoceros beetles today contain some of the most spectacular insects on Earth because of the large size and extravagant horns in the males of some species.

"There have been only a handful of rhinoceros beetle fossils discovered and named previously, but none approach Oryctoantiquus borealis in size or age," he said.

The largest known fossil scarab had been Cheirotonus otai, a 45 mm long-arm chafer (not a rhino beetle) from the Middle Miocene in Japan. The new species is 50 mm in length.

The new genus name, Oryctoantiquus, comes from the Greek "oryktes," which means digger, and the Latin "antiquus", meaning old, while the species name, "borealis", means northern in reference to its northerly location in Oregon.

The discovery of O. borealis has caused a stir among entomologists who study scarab beetles, because its location proves large rhinoceros beetles existed in northwestern North America 38 million years before the Panama land bridge became established 7 million years ago.

The fossil demonstrates that large rhinoceros beetles entered North America earlier from other areas, possibly Asia.

"We had not previously known of any living, large rhinoceros beetles in North America that did not originate from tropical regions of Central or South America," Ratcliffe said.