Gomphotheres, ancient ancestors of the elephant, lived longer than previously believed, according to a University of Arkansas study.

Gomphotheres were smaller than mammoths and their size was similar to the modern elephants. Until now, the ancient creatures were thought to have disappeared from North America much before the early humans entered the continent, some 13,000 -13,500 years ago, during the late Ice Age.

Beginning 2007, archeologists discovered skeletal remains of two juvenile gomphotheres along with artifacts of the prehistoric Clovis (the earliest group of hunter-gatherers to inhabit North America) culture at an archaeological site in northwestern Sonora, Mexico.

The bones including a fossilised jawbone with teeth dated back to approximately 13,400 years making them the last known gomphotheres in North America. The finding is based on radiocarbon dating of the bones.

"This is the first Clovis gomphothere. it's the first archaeological gomphothere found in North America, it's the first evidence that people were hunting gomphotheres in North America, and it adds another item to the Clovis menu," archaeologist Vance Holliday, who co-authored the paper, said in a statement.

Clovis artifacts included signature Clovis projectile points, spear tips, cutting tolls and flint flakes from stone tool-making. The Clovis culture is popularly known for its distinctive stone tools.

Researchers said that the discovery of mingled bones suggest that the Clovis community most likely hunted and ate gomphotheres. Their culture was already well-known as hunters of the gomphotheres' cousins - mammoths and mastodons.

"Although humans were known to have hunted gomphotheres in Central America and South America, this is the first time a human-gomphothere connection has been made in North America," said Holliday.

The finding is published in the Journal Proceedings of the National Academy of Sciences.