Artist's view of Thomas Farm, Gilchrist County, northcentral Florida, 18 million years ago. A pack of coyote-like predators, Metatomarctus, threaten a three-toed horse, Parahippus. Numerous fossils of both of these animals, and many others, have been collected at Thomas Farm since the 1930s. The open landscape of the drawing is misleading; the habitat around the sinkhole that formed the fossil site was probably much more wooded. (Adapted from Biological Sciences Curriculum Study, American Institute of Biological Science.)