A bachelor party celebrating with a hiking trip near Albuquerque, N.M., on Monday stumbled into an incredible find: the skull of a stegomastodon, a prehistoric elephant.

While walking around Elephant Butte Lake State Park about 150 miles outside of Albuquerque, Antonia Gradillas, 31, and his friends noticed something unusual.

"As we were walking we saw a bone sticking out about one or two inches from the ground," Gradillas told ABC News.

Soon after they started digging, the group noticed the skull, and Gradillas realized the find could be a big one. He contacted a friend and was directed to Gary Morgan, a paleontologist with the New Mexico Museum of Natural History and Science, who came to the spot with a crew the very next day.

The museum crew dug up the fossil and then prepared it to be moved on Thursday. According to Morgan, the skull came from a stegomastodon that stood around 9 feet high and weighed more than 6 tons, ABC News reported.

"This is the coolest thing ever," Gradillas said. "Some people with Ph.D.s in this field might not even have this kind of opportunity. We were so lucky."

While the creature is estimated to have been about 50 years old when it died, Morgan and the crew don't know how it died or whether it was male or female.  

Of his two decades in the field, Morgan called the find the "most complete elephant skull of any kind" that he's seen, the Associated Press reported. 

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