SUBORDER E AMBLYPODA 219 



According to Diirst, B. planifrons is the ancestor of B. primigenius, whereas 

 B. aculifrons and B. namadicus Falconer are allied to the Bihovina and the 

 zebra. The fossil aurochs, B. primigenius Bojanus, the Urus of Julius 

 Caesar, inhabited Europe, but was also distributed throughout Asia and North 

 Africa. 



Suborder E. AMBLYPODA Cope.i 



Extinct, usually large plantigrade ungulates with short, pentadadyl feet and 

 broad terminal phalanges provided with hoofs ; second row of carpals alternating with 

 the first. Astragalus very broad and low, articulating with tibia and fibula, the 

 articulating surface for the tibia very slightly concave and sr)iooth, not hollowed out. 

 Dentition usually complete. Cheek teeth brachyodont and lophodont. Brain very 

 small. 



The Amblypoda comprise some of the largest terrestrial mammals of the 

 Eocene. Their limbs, dentition and entire skeletal structure, besides showing 

 many primitive characters, have also become highly specialised as regards 

 certain features, which are found also, to some extent, among Perissodactyls, 

 Artiodactyls, Proboscidea and Astrapotheria. 



They begin in the Puerco strata (basal Eocene) with rather small and 

 slender forms (Pantolambda), which are of a primitive nature as shown by the 

 tritubercular upper molars and the semidigitigrade extremities. The robust 

 and large-sized Coryphodonts having a complete dentition, in which the molars 

 have become lophodont, occur in the Wasatch beds, and in the early Eocene 

 strata in Europe. More highly differentiated are the giant Upper Eocene 

 Dinoceratidae, found only in North America. Here the upper incisors are 

 reduced and the upper canines protrude over the lower jaw as great tusks. 

 The lower canine, on the other hand, has become greatly reduced, as is true 

 also of the incisors. The cheek teeth become distinctly lophodont and the 

 premolars molariform. 



The extremities are stout, rather high and pentadactyl. The carpals are 

 disposed in slightly alternating rows ; a centrale is sometimes present. In 

 the pes the tarsals show a strong, lateral displacement. The low, extremely 

 broad astragalus covers not only the navicular, but, in contrast to the Probo- 

 scidea, also a large part of the cuboid bone. The navicular rests on the three 

 cuneiform bones. The astragalus lacks a well-defined head, as well as a true 

 trochlea, in which the weakly developed articulating surface of the tibia 

 makes no depression. For this reason only a very slight flexion of the pes is 

 possible. There is an astragalar foramen, besides a facet on the internal side 

 of the astragalus for a so-called tibiale (sesamoid), as is also the case 

 in Condylarthra. The calcaneum and the short, stout metatarsals are very 

 like those of the proboscidian foot. There is a third trochanter on the femur 

 in the earliest forms, but this is lacking in the Dinoceratids. The fibula 

 articulates in these forms only with the astragalus. 



^ Cope, E. D., The Amblypoda. Amer. Naturalist, 1884-85. — Earle, Charles, Revision of 

 the Species of Coryphodoa. Bull. Amer. Mus. Nat. Hist., 1892. — Gidley, J. W., New Paleocene 

 Mammal. Proc. U.S. Nat. Mus., Wasliington, 1917.— Hebert, Edmond, Ann. Sci. Nat., 1856 

 (Zool. ), p. 87. — Marsh, 0. C, Amer. Journ. ScL, 1877-81. A Monograph of the extinct order 

 of gigantic mammalia, Dinocerata, Rept. U.S. Geol. Survey, 1884. — Oshorn, H. F., Complete 

 Skeleton of Coryphodon and Evolution of the Amblypoda. Bull.. Amer. Mus. Nat. Hist., 1898. 

 Skull of Bathyopsis. Ibid., 191^. 



