Among the discoveries was the skull of an animal that appears to be an entirely new genus within the same family as otters, skunks and weasels.
"It just blew me out of my mind," Xiaoming Wang, associate curator of vertebrate paleontology at the Natural History Museum of Los Angeles County, said after seeing the fossil of the badger-like animal. "It looks like it was very ferocious."
A team led by paleontologist J.D. Stewart recovered bones from 25 species of vertebrates, as well as birds and snails, that date to roughly 15 million years ago. The best-preserved 1,200 specimens now make up a permanent collection at the University of California, Berkeley's Museum of Paleontology.
The dig is a legacy of California's power crisis of 2000-2001. The fossils were unearthed during construction of new electricity transmission lines at the so-called Path 15, the infamous utility bottleneck in the state's north-south electricity conduit near Los Banos.
Also found on the site just west of Fresno were the most complete remains yet discovered in the San Joaquin Valley of a bear-dog creature that ruled what once was a savannah-like environment.
Stewart, a research associate at the National History Museum in Los Angeles, said his team found a jaw bone and an inch-long fang from what they estimate was a 200-pound creature.
"They look something like a large pit bull," Stewart told the San Francisco Chronicle. "They're very tough customers."
Also found was the most complete skull ever of the early horse Merychippus californicus, Latin for "ruminant horse of California."
The three-toed horse stood only 3 1/2 feet tall from its shoulders to the ground, said Stewart, adding that the animal marks a milestone on the evolutionary path of horses.
"Horses are getting bigger," he said. "They've got one toe, and their teeth are getting longer. You may not want to call it evolution. Call it what you want. That's what the evidence shows."
Long after the dinosaurs, the horses thrived in the middle part of the Miocene Epoch, during what the Florida Museum of Natural History's Web site calls "the heyday or 'hayday' of horses," referring to the change in diet.
Another find -- two-thirds of a giant tortoise shell -- marked the most complete remnant of the ancient creature ever found in California.
"Very little is known about the West Coast tortoises," said renowned turtle expert and retired paleontologist Howard Hutchison. "It's really about the first time ever when you can say with some certainty that it's linked to the ones found in the Great Plains."