. The age of mammals in Europe, Asia and North America. Mammals, Fossil; Paleontology. 164 THE AGE OF MAMMALS the absence of upper cropping teeth, and in the presence of spear-hke tusks and two pairs of prominent osseous horns. The body is intermediate in proportion between those of the elephant and rhinoceros. The feet are extremely short and broad. The brain (Fig. 71) is no larger than that of a dog, out of all proportion to the body, and essentially of the archaic type. These animals are very abundant both in the Upper Bridger and Lower Washakie, and serve to tie these formations into a sin
. The age of mammals in Europe, Asia and North America. Mammals, Fossil; Paleontology. 164 THE AGE OF MAMMALS the absence of upper cropping teeth, and in the presence of spear-hke tusks and two pairs of prominent osseous horns. The body is intermediate in proportion between those of the elephant and rhinoceros. The feet are extremely short and broad. The brain (Fig. 71) is no larger than that of a dog, out of all proportion to the body, and essentially of the archaic type. These animals are very abundant both in the Upper Bridger and Lower Washakie, and serve to tie these formations into a single life-zone. Of the creodont Carnivora the small hysenodont Sinopa is becoming somewhat more rare. The large, powerful creodont Potriofelis of the family Oxyaenidae, analogous in its proportions on a powerful scale to the modern wolverine (Gulo), and in its dentition to Hycena and Synoplotherium, was capable of attacking the largest contemporary mammals. Here also the skulking and swift-footed Mesonyx (or Dromocyon, Mesonychidse) is represented by species of intermediate size (Fig. 52). Of the modernized. Fig. 61. — The armadillo in North America. Skeleton of the Middle Eocene Metacheiromys tatusia of the Bridger formation. In the American Museum of Natural History. ungulates the tapirs (Isedolophus) occur, but are rare. The horses (Oro- hippus) as well as the primates (Notharctidse) are in a somewhat more advanced stage of dental evolution than in the Lower Bridger levels. The titanotheres now become polyphyletic through the appearance of three additional phyla (Telmatherium, Manteoceras and Mesatirhinus) in ad- dition to the extremely broad-headed Palceosyops Thus indications of at least five phyla of titanotheres now occur, including long-headed forms with more hypsodont teeth, and short-headed forms with more brachyo- dont teeth. Of great interest is the development of rudimentary horns on the forehead above the orbits, which appear as 'rectigradations,' in all of these
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpaleontology, bookyea
