Paleontologists are examining a "huge" fossil find in Southern California, comprising 1,500 bone fragments from animals that lived up to 1.4 million years ago.

The discovery included bones belonging to a giant cat that was the ancestor of the sabre-toothed tiger, ground sloths the size of modern-day grizzly bears, camels and other species.

In all, the fossils represented 35 species from the Irvingtonian period, which began 1.8 million years ago and ended 300,000 years ago.

The cache of animal bones was unearthed by a utility company that was preparing to build a new power station in San Timoteo Canyon, 136 kilometres southeast of Los Angeles.

It is now an arid and dusty area but one million years ago it was part of a lush river valley.