Evolution Diary

After the dinosaurs perished, life on Earth didn’t take long to bounce back, a new study suggests.

A newfound 60-million-year-old creature called Eritherium azzouzorum—the oldest known elephant ancestor—bolsters the case that whole new orders of mammals were already around less than 6 million years after global catastrophe ended the age of reptiles some 65.5 million years ago.

(See “Did Rising Oxygen Levels Fuel Mammal Evolution?”)

Paleontologist Emmanuel Gheerbrant discovered the rabbit-size proto-elephant’s skull fragments in a basin 60 miles (100 kilometers) east of Casablanca, Morocco.

Elephant ancestors, he said, now join the likes of rodents and early primates as some of the first known mammals to walk the Earth during the Paleocene era, 65.5 to 55 million years ago (prehistoric time line).

Much of the story of the newly discovered creature, said Gheerbrant, of the National Museum of Natural History in Paris, can be found in its teeth. Two of the creature’s lower front teeth jut a fraction of an inch out from its jaw. No other fossils of the time have teeth like this.

“This is some kind of precursor of the tusk of the more modern [elephant],” Gheerbrant said.

Based on the skull fragments, Gheerbrant guessed that the proto-elephant was probably no more than 20 inches (50 centimeters), tip to tail—”something like a very large rabbit,” size wise.

Because the find consists of skull and jaw fragments only, Gheerbrant said there’s not enough evidence to know what it looked like—or whether it had anything resembling a trunk or elephantine ears.

Sixty million years ago, Africa was lush with vegetation and disconnected from the Eurasian continent to the north (world map of this period). The continent, Gheerbrant said, was an evolutionary hotbed.

The rise of elephant-like mammals hot on dinosaurs’ heels suggests there are many more mammals from the period to be found, he said. More fossil hunts are needed, he added, to uncover how evolution put mammals center stage once the reptilian resource hogs had gone.

News from National Geographic