772 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



ABC D 



Figure 700. — Carpus of the Eocene perissodactyls (horses, tapirs, lophiodonts, paleotheres, and rhinoceroses) 



Primitive tetradactyl; magnum small, covered by large "centrale" process of 

 scaphoid; little or no contact with lunar in front; contact normal in back: 



A, Hcptodon calciculus, Am. Mus. 294 (Lophiodontidae), lower Eocene. 



B, Systemodon primaevum. Am, Mus. 15807 (Tapiridae). lower Eocene. 



C, Lambdotherium popoagkum. Am. Mus. 4880 (Brontotheriidae). lower Eocene 



D, Eotitanops princeps, Am. Mus. 296 (Brontotheriidae), lower Eocene. 



E, JSomoropus amaroTum, Am. Mus. 5096 (Chalicotheriidae), middle Eocene. 

 Functional tetradactyl; magnum increasing, "centrale" process of scaphoid becom- 

 ing reduced, lunar-magnum contact increasing: 



F, Isectolophus sp.. Am. Mus. 12219 (Tapiridae), middle Eocene. 



G, Isectolophus annectens. Princeton Mus. (Tapiridae), middle Eocene. 



H, Hyrachyus, Am. Mus. 12664 (Hyracodontidae), middle Eocene. 



I, Hyrachyus, Am. Mus. 1602 (Hyracodontidae). middle Eocene. 

 Isotridactyl; magnum vertical, narrow, lunar-magnum contact diminishing: 



J, Triplopus cubitalis, Am. Mus. 5095 (Triplopodinae), middle Eocene. 



K, Colodon, Am. Mus. 658 (Helaletidae), middle Eocene. 



L, Lophiodon, after Dep6ret, Lyons Mus. (Lophiodontidae), middle Eocene. 



M, Palaeotherium, after De Blainville (Palaeotheriidae), middle Eocene. 

 Monodactyl; magnum broadening, lunar-magnum contact increasing: 



N, HyTacotheriitm (Equidae), lower Eocene. 



O, Epihippus (Equidae), middle Eocene. 



P, Mesohipptis (Equidae), lower Oligocene. 



