By Lisa Maria Garza

DALLAS (Reuters) - A North Texas family, who discovered the skeleton of a 20,000- to 40,000-year-old mammoth while mining through sediment on their farm, is preparing to turn over the remains to a local museum.

In May, Wayne McEwen and his family were gathering material from a gravel pit on their property, south of Dallas, when his son struck a 6-foot (1.8 meter) tusk while operating an excavator.

The rest of the near-complete skeleton was unearthed by a team from a nearby community college, who determined it was a Columbian mammoth - a slightly larger, less hairy version of the more famous woolly mammoth.

The family decided to donate the remains to the Perot Museum of Nature and Science in Dallas.

Ron Tykoski, a paleontologist with the museum who is working with a team to prepare the specimen for transport, said the remains are missing a few leg bones but are mostly intact.

"We get a lot of mammoth fossils in Texas but it's usually a tooth here, a tusk there or a piece of jaw," Tykoski said on Tuesday.

"This is unusual. It looks like it just laid down and died."

There is no sign the carcass was disturbed by scavengers, likely because flood waters covered it with silt shortly after its death, he said.

The mammoth is believed to be a female because of its small size, the length of the tusks and the flare of the pelvic bones.

The animal was approximately 8-9 feet (2.4-2.7 meters) tall at the shoulder, or similar in size to a modern-day female Asian elephant.

"It needed to stay in North Texas where the local communities can enjoy it for a long time to come," McEwen said in a news release.

(Reporting by Jon Herskovitz; Editing by Sandra Maler)