ocr: ing, is the grouping of organisms by shared, specialized characteristics; each time a new evo- lutionary feature appears, a new branch grows on the evolutionary tree, comprising organisms that have both the old traits and the new one. Thus some later horses, such as Calippus, num- ber 46, are actually smaller than earlier ones, and other later horses, such as Neohupparton, number 40, still retain three toes. So we have here both a classic demonstration of evolution and a paradigm of scientific method at the Museum. Much of the history of horses was passed in North 17 - America, the conti- nent ...