A huge old predator found in a museum drawer

Larger than a polar bear, with a skull the size of a rhinoceros, a predator of 22 million years ago previously unknown is calling Simbakubwa kutoaafrika has been identified by US researchers.

Nancy Stevens and Matthew Borths of University of Ohio discovered the animal by studying fossils stored in a drawer of the National Museum of Kenya.

"We've seen a row of gigantic meat-eating teeth, clearly belonging to a new species in science," says lead author Borths.

Further research has found most of the jaw, parts of the skull, and some other skeletal remains.

Simbakubwa means "big lion" in Swahili, but the creature was not a kind of big cat any more than it was related to any carnivore alive today. This was a member of a group known as hyaenodonts.

Hyaenodonts are thought to have originated in Africa during the Paleocene, 66 to 55 million years ago, before spreading north and east in Europe and Asia. They have been predators for nearly 45 million years after the demise of non-avian dinosaurs, before turning off 18 to 15 million years ago.

"We do not know exactly what led the hyaenodontes to extinction, but ecosystems have rapidly changed as the global climate has become drier," Borth said.

"The gigantic parents of Simbakubwa were among the last hyaenodontes on the planet. "

While this species lived, hyaenodontes spread north and intersected with the ancestors of today's cats, dogs, and hyenas.

"This is a fascinating period of biological history," says Borths.

"Lines that have never met begin to appear together in the fossil record."

The discovery highlights the importance of museum collections, say the researchers.

"It's an essential fossil that demonstrates the importance of museum collections in understanding the history of evolution," says co-author Stevens.

"Simbakubwa is a window on a bygone era. When ecosystems moved, a key predator disappeared, announcing Cenozoic faunal transitions that ultimately led to the evolution of modern African fauna. "

The discovery is reported in the Journal of Vertebrate Paleontology.