Man discovers giant glyptodon shell in his back yard

A giant egg-shaped shell found in an Argentinian's back yard on Christmas day could be more than 10,000 years old.

A man, identified by local media only as Joseph, stumbled across the ancient fossil poking out of a creek bed behind his property near Buenos Aires.

He bolted to find his family and tell them he discovered  a "large dinosaur egg," but they did not believe him.

However experts have now taken a look and believe the scaly and cracked object belonged to a glyptodon.

Palaeontologist Laura Cruz told TN it was a shell from the mammal, which has been extinct for about 10,000 years.

"They (glyptodon fossils) are commonly found in Argentina and Brazil," she said.

The giant mammals were the ancestors of modern day armadillos and could grow as large as a Volkswagen Beetle.