An amateur Montana fossil hunter stumbled across a major discovery more than a decade ago when bones he found turned out to be a new species of dinosaur, researchers announced.

Retired nuclear physicist Bill Shipp discovered the leg bone for “Judith”, known to scientists as Spiclypeus shipporum, after he hired an amateur paleontologists to teach him how to search for fossils, The Associated Press reports.

(AP (AP)

Judith, named for the Judith River rock formation near where it was found, is believed to be a close family member of the more well known horned dinosaur, the triceratops, researchers said in a report published in the PLUS ONE scientific journal. It lived in what would become Montana nearly 7million years ago.

Scientists unearth 'supercroc' that dined on dinosaurs Show all 2 1 /2 Scientists unearth 'supercroc' that dined on dinosaurs Scientists unearth 'supercroc' that dined on dinosaurs 264538.bin Professor Paul Sereno with 'supercroc' Mike Hettwer/National Geographic Scientists unearth 'supercroc' that dined on dinosaurs 264539.bin A drawing of 'boarcroc' Todd Marshall/National Geographic

“I found it accidentally on purpose,” Mr Shipp told the AP. “I was actually looking for dinosaur bones, but with no expectation of actually finding any.”

Researchers found evidence of infection in the 15-foot, four ton plant-eater’s leg, that research Jordan Mallon said would have left the animal vulnerable to predators.

“It’s an exciting story, because it’s a new species, and yet we have this sort of pathetic individual that suffered throughout its lifetime,” Mr Mallon, a paleontologist at the Canadian Museum of Nature, said.