ENVIEONMENT OF THE TITANOTHERES 



71 



last surviving species of Coryphodon and of the con- 

 dylarth Phenacodus among the archaic ungulates. 

 The presence of the condylarth Meniscotherium 

 serves to correlate the Wind River with the upper 

 levels ("Largo beds") of the Wasatch of New Mexico. 

 While the Wind River life on the whole represents 

 a continuation of that of the preceding stages of the 

 Wasatch, with which it possesses several genera and 

 eleven species in common, it also includes nine new 

 genera that survive in the Bridger formation of 

 middle Eocene time. The Wind River marks the 

 end of the lower Eocene, the last period of certain 

 highly distinctive lower Eocene forms like Cory- 

 phodon, but it is also prophetic of the middle Eocene 

 in the presence of lemuroids like Notharctus, Anapto- 



somewhat like a slender, diminutive tapir in body 

 proportions. In skull structure and dentition Eoti- 

 tanops foreshadows the true titanotheres of the 

 middle Eocene; its feet are more slender than those of 

 its successors, and it was doubtless a more agile animal. 



The special life conditions surrounding these early 

 titanotheres are more fully set forth in the descriptions 

 of the Wind River titanotheres in Chapter V, section 3. 



Olimate and physiography during the deposition of 

 the Wind River and Green River sediments. — For Wind 

 River life in general the reader is referred to section 3 

 of this chapter. Here we may speak of the whole 

 basin region. 



While fluviatile and flood-plain sediments were 

 being deposited in the Wind River Basin of northern 





f!t» - ""."-i**^*, 



Figure 47. — A typical "Lost Cabin" locality, on the north side of AlkaU Creek about 8 miles east of Lost 



Cabin, Wind River Basin, Wyo. 



Lambdotherium-Eotitanops- Coryphodon zone (Wind River B). A characteristic view of tlie red-banded beds that have yielded the greater part of 

 the fauna of the Lambdotherittm zone. (Compare PI. VI, B.) After Granger (1910.1), Am. Mus. negative 17792. 



morphus, and Shoshonius; of true doglike or civet-like 

 carnivores like Viverravus and Vulpavus; or of rodents 

 like Sciuravus and Par amy s. Remains of Equidae 

 are rather rare and are represented by several species 

 of Eohippus, of which E. venticolus is the most pro- 

 gressive, and those of titanotheres, especially Lamb- 

 dotherium, are very abundant. 



Lambdotherium, one of the earliest titanotheres, 

 was a small, light-limbed form, about the size of a 

 coyote {Canis latrans). It represents a distinct 

 cursorial side branch of the titanothere family, re- 

 sembling the contemporary horses and lophiodonts 

 in its light limb and foot structure. Eotitanops 

 ("the dawn titanothere") was a true and very primi- 

 tive titanothere about the size of a sheep {Ovis aries), 



Wyoming there lay to the south a large, shallow lake, 

 covering about 5,000 square miles, in which were 

 deposited 800 feet of impure limestone at the base, 

 followed by about 1,200 feet of thin, fissile calcareous 

 shale. (King, 1878.1, p. 381.) The deposition of 

 these lake sediments (Green River) began near the 

 end of Wasatch time. They contain abundant and 

 well-preserved remains of insects and fishes. The 

 presence of sting-rays and other fishes of marine or 

 coastal type indicates that these originally marine 

 forms had become landlocked, as did the existing 

 marine survivors in the Caspian Sea and Lake Titicaca. 

 Many of the fishes of the Green River shales are related 

 to forms now found chiefly in the southern continents, 

 especially South America. 



