Cleaning up construction sites, Ralph Timpano and...

Cleaning up construction sites, Ralph Timpano and Sally Mason have probably come across a lot of four-by-fours. In Hermosa Beach, they found one that ended up in a museum.

The discovery wasn’t the usual wooden discard, but a second cervical vertebra from a Bison antiquus, an extinct animal similar to the American buffalo. The animals roamed the area between 7,000 and 50,000 years ago, said Michael Stokes, a senior technician for the Los Angeles County Museum of Natural History.

Timpano, of Redondo Beach, found the pinkish-tan bone, which measures 4 inches by 4 inches by 1 1/2 inches, in the 900 block of 15th Place two weeks ago while cleaning up the construction site of a new house.

“It’s one of the more exciting things we’ve found in our cleanup jobs,” said Mason, who was there watching. “Usually our exciting finds are limited to old rusty wrenches or something.”

Timpano probably would have thrown the bone away, but Mason said she realized it was unusual.

“It was more like a heavy plaster than a bone; bones are light and airy,” she said. “It looks like a larger-than-normal bone, not something that you would find from a steak.”

But a steak bone is all that museum officials found when, excited by the B . antiquus find, they went to the site a week later to search for more bones. It is unlikely that other bison bones will be found at the site, he said, because the dirt found inside the bone does not match the soil in Hermosa Beach.

The bone is not an exceptional find, Stokes said, and B . antiquus bones are commonly found in the La Brea Tar Pits. The bone, which Mason is donating to the museum, will become part of the museum’s educational collection, Stokes said.

What is important, he emphasized, was that an individual took the time to have the bone checked out. Occasionally, people take bones to the museum that turn out to be from dogs or cats, but Stokes said even that is appreciated.

“We get 49 people who come in like that, and we get one person that has something really spiffy. . . . Or you could take it home and put it on your mantel or use it for a doorstop for years and years and years and never know what it is.”