A rare fossil of a mastodon skull was discovered by a group of men attending a bachelor party at a lakeshore in a New Mexico state park, a museum spokesman said on Thursday.

The fossil was found, complete with its tusks, in the sand earlier this week in Elephant Butte State Park, an area of arid hills surrounding a reservoir about 155 miles (250 km) south of Albuquerque, Randall Gann of the New Mexico Museum of Natural History and Science said.

According to Reuters, the museum's head paleontologist called it "the most complete mastodon skull with attached tusks he has seen in 20 years."

"As we are cruising by we see a large tusk or what seems to be a large tusk coming out of the ground about a good three to four inches out," Antonio Gradillas told CBS affiliate KRQE News 13.

Gradillas and his friends started digging and found what appeared to be the giant remains of a prehistoric elephant skull, CBS News reported.

Known to be Ice Age relatives of the elephant, Mastodons used to stand 10 feet (3 meters) tall and migrated to North America some 15 million years ago. Before becoming extinct about 10,000 years ago, they ranged across the continent with saber tooth tigers, giant sloths and American camels.

A professor at the University of New Mexico was initially contacted by the group, who then put them in touch with the museum's head paleontologist Gary Morgan.

Gann said scientists from the museum planned to act quickly.

"Because it is in sand and not buried in rock, Dr. Morgan feels he can excavate the skull, cast it, and remove it today," the spokesman said.

The area has been blocked off for a small team of paleontologists to work on excavating the fossil.

"(The skull) looks virtually 100 percent complete, a very important scientific discovery that we may put on public display," said Morgan.

The group was praised by Beth Wojahn, spokeswoman for New Mexico's Energy, Minerals and Natural Resources Department.

"What is noteworthy is the men who found the skull did not disturb it and called the right people," Wojahn said.