Larger than a polar bear, with a skull the size of a rhinoceros, a previously unknown 22-million-year-old apex predator named Simbakubwa kutoaafrika has been identified by US researchers.
Nancy Stevens and Matthew Borths from Ohio University discovered the animal while investigating fossils stored in a drawer at the National Museum of Kenya.
“We saw a row of gigantic meat-eating teeth, clearly belonging to a species new to science,” study lead author Borths says.
Further searching turned up most of the jaw, parts of the skull, and a few other skeletal remains.
Simbakubwa means “big lion” in Swahili, but the creature was not a species of big cat, nor was it related to any carnivores alive today. It was a member of a group known as hyaenodonts.
Hyaenodonts are believed to have originated in Africa during the Paleocene, 66- to 55-million years ago, before spreading north and east into Europe and Asia. They were apex predators for some 45 million years after the non-aviary dinosaurs died out, before going extinct themselves between 18 million and 15 million years ago.
“We don’t know exactly what drove hyaenodonts to extinction, but ecosystems were changing quickly as the global climate became drier,” says Borth.
“The gigantic relatives of Simbakubwa were among the last hyaenodonts on the planet.”
During the time this species lived, the hyaenodonts were spreading north and crossing paths with the ancestors of today’s cats, dogs, and hyenas.
“It’s a fascinating time in biological history,” Borths explains.
“Lineages that had never encountered each other begin to appear together in the fossil record.”
The finding highlights the significance of museum collections, the researchers say.
“This is a pivotal fossil, demonstrating the significance of museum collections for understanding evolutionary history,” co-author Stevens says.
“Simbakubwa is a window into a bygone era. As ecosystems shifted, a key predator disappeared, heralding Cenozoic faunal transitions that eventually led to the evolution of the modern African fauna.”
The discovery is reported in the Journal of Vertebrate Paleontology.