Most people are unaware that California was once populated by tortoises as large as those found on the Galapagos Islands of today, large enough that a person could have literally taken a ride on its back. The remains were found in the Tehama Formation that was deposited in the area when the coast range was beginning an active uplift and debris washed down creeks and rivers to be deposited in the north valley as mud, sand and gravel. These sediments entrapped the bones of numerous animals that were then preserved as fossils. Because the Tehama formation lies above a dated volcanic ash that covered much of the north state about 3.3 million years ago it is assumed that the fossils are about 3 million years old. Only in recent time have these sedimentary rocks been uplifted and now eroded to expose these ancient remains.
These remains were discovered by local hunters Mike Higley (on the right in the photo) and John Rhea Jr. (on the left in the photo). The excavation team members were Richard Hilton, Charles Dailey, and museum technician George Bromm. Volunteers at the site included John Rhea Jr., Mike Higley, Patrick Antuzzi and James Readle.
Found in the vicinity of the tortoise were the partial remains of a large extinct cat that was bigger than a bobcat but smaller than a mountain lion. Other fossils included those of horse, deer, camel, bear and even a pond turtle. In other areas the Tehama Formation has yielded additional animal remains, giving us a clearer picture of the 3 million-year-old ecology. These include mastodons (extinct relatives of elephants), hyena-like dogs, giant ground sloths (who originally made their way here from South America) and various species of rodents and birds.
These tortoise remains may be the most complete of any of the giant tortoises found in California and according to fossil turtle and tortoise specialist, Dr. James Parham, they may be of an as yet undescribed species.Find out more about turtles and tortoises through the California Turtle and Tortoise Club.