Workers digging at a downtown San Diego construction site have uncovered the prehistoric remains of an 2.4-meter mammoth. A backhoe operator working at the Thomas Jefferson School of Law site unearthed a 6.1-meter tusk Wednesday. School spokesman Chris Saunders said experts called in from the San Diego Natural History Museum uncovered the animal's skull and other bones. Museum paleontologist Pat Sena said it's a "pretty important find" and that it's rare to find mammoth remains with such an intact skull, foot bones and tusk. Full-sized mammoths, about 2.4 to 4.3 meters tall like elephants, became extinct around 10,000 years ago. But experts believe the specimen found this week dates back as far as a half-million years ago.