Scientists went to work digging for fossils at La Brea Tar Pits, digging the tooth of a 5-foot (1.5-meter) dire wolf and the toe of a sabertooth tiger from the sticky prehistoric asphalt near downtown Los Angeles. About 10,000 years before the arrival of mammoth traffic jams in the second-largest U.S. city, the two beasts likely got stuck in the goo while hunting a camel, horse or ground sloth, said John Harris, chief curator and head of vertebrate studies at the Natural History Museum of Los Angeles County, which oversees the site. ''It's one of the, if not the, richest...