MERCED -- The discovery of mammoth bones and other fossils in Merced County last week uncovered a historic piece of the valley's past, dating to the end of the last ice age.
Along with Columbian mammoths, paleontologists found partial remains of bison, horses, camels and antelope, according to the California Department of Transportation. The remains were discovered during work on the $128 million Highway 99-Arboleda Drive Project, where a new interchange is being constructed.
"The fossils are fairly common in the valley, but discoveries are rare, especially the size of the discovery," said Blake Bufford, director of the Fossil Discovery Center of Madera County in Chowchilla. "A lot of times it's an individual bone or animal, but they found a fairly large variety of remains."
Bufford said it wasn't unusual for mammoths to roam in the valley centuries ago, but the bison discovery indicates the remains are from a later period in time.
Bison entered North America from Siberia about 200,000 years ago, he said.
Paleontologists discovered roughly 20 individual bone specimens, ranging in size from fragments of a pond turtle shell to a mammoth skull. They also found teeth, tusks, and rib, shoulder and limb bones.
Based on the geologic formation, Robert Dundas, associate professor of vertebrate paleontology at California State University, Fresno, said the fossils could be 10,000 to 70,000 years old.
It's fairly unusual to find such a large variety of remains in one place, Dundas said.
"It's exciting because even though there are a number of fossil sites up and down the San Joaquin Valley, we rarely find such a large concentration of fossil remains of that many species at one site," he said.
The California Department of Transportation prepares for fossil discoveries whenever they dig more than 5 feet deep, or at certain project sites, depending on the type of soil. Scientists say fossils are usually found near sedimentary deposits.
For this freeway project, which began in July, Caltrans called on trained paleontological monitors to follow the heavy equipment. "Caltrans prepares for any type of historical finding with a paleontologist on site from Day One," said Angela DaPrato, Caltrans spokeswoman.
When the discovery was made, DaPrato said work was stopped in that area and workers moved to a different part of the project.
After excavation, paleontologists wrapped the fossils in plaster jackets to keep them in place while they were transported to a Caltrans warehouse for storage, then to a lab to be prepared, identified, and documented.
DaPrato said there could be more fossil discoveries as the Merced construction project continues. It is slated to end in 2015.
Bufford agrees. "Most fossil discoveries are accidental," he said. "But paleontologists keep their eyes on those areas because there could be more."
Finding a permanent home for the fossils is next. DaPrato said Caltrans is working with the University of California at Merced to find a place in the Central Valley, possibly a museum or library to display the fossils.
"We are trying to work with our local agencies to find a home for the fossils so people in the Central Valley can enjoy them."