In November 2016, a nine-year-old was on a walk with his family in Las Cruces, New Mexico, when he tripped, fell and found himself in front of something that looked to him like fossilised wood.

News reports say what Jude Sparks found that day was the fossilised skull of a 1.2 million-year-old stegomastodon, a long-extinct distant cousin of ancient mammoths and current-day elephants. In May, it was excavated.

Sparks, now 10 years old, said, “It was just an odd shape. I just knew it was not something that you usually find,” reported The New York Times. The boy said it looked like a huge jaw, while his younger brother thought it was just a big cow and his parents thought it was an elephant.

The Sparks family then sought help from New Mexico State University biology professor Peter Houde, who identified it and eventually helped to get the fossil excavated after months of work on getting permits and money.

Houde estimates the jaw weighs about 120 pounds (about 54 kg) and the entire skull about one tonne. The skull may appear to be strong, but it is quite delicate, he said in a statement released by the New Mexico State University.

“The upper part of the skull is deceiving. It’s mostly hollow and the surface of the skull is eggshell thin,” Houde said. He added that he hopes the fossil would be exhibited at the university eventually.