Published online by Cambridge University Press: 17 July 2017
The evolution of certain mammalian lineages has become the favorite examples of nearly every introductory textbook in historical geology, paleontology, and evolutionary biology. The evolution of the horse is the most frequently used, since it emerged in 1851 and has been reproduced many times in nearly 150 years (see Gould, 1987, and MacFadden, 1992). Occasionally, one sees a revival of one of Osborn's (1929) evolutionary sequences of brontotheres, and some books may show a sequence of mammoths and mastodonts. In most historical geology books, the discussion of fossil mammals usually consists of just these selected examples, since the authors seem to think that a fuller account of Cenozoic mammal evolution is beyond the level of their readers. Children's books, trade books, and museum displays typically show little more than the evolution of the horse and few selected pictures of spectacular beasts such as saber-toothed cats, ground sloths, mammoths, and the gigantic hornless rhinoceros Paraceratherium (called by the obsolete names Baluchitherium or Indricotherium in virtually every caption). Given these conditions, one cannot fault students or the general public for thinking that only horses have a good fossil record, or that there are no other well-studied groups of fossil mammals.