ENVIKONMENT OF THE TITANOTHEEES 



65 



characteristic of the Sparnacian of France. Notho- 

 dectes of the "Tiffany beds" is particularly interest- 

 ing because of its structural affinity to Plesiadapis 

 of the Cernaysian of France. The multituberculates 

 are represented in Wyoming by Ptilodus (" Sand 

 Coulee" and "Clark Fork"?). Of the four specimens 

 of ptilodontids from Wyoming, one found by Granger 

 was from the Big Horn B horizon ("Sand Coulee 

 beds"). Three found by Stein were probably from 

 the same horizon but may have been from the under- 

 lying Big Horn A horizon (the "Clark Fork beds"). 

 Undoubtedly ptilodontids occur in the "Clark Fork," 

 but we can not furnish any positive evidence (W. 

 Granger, 1919). 



This mammal fauna as a whole actually resembles 

 that of the Torrejon more closely than that of the 

 lowest overljang horizon (Big Horn B, "Sand Coulee") 

 of the Wasatch. A significant discovery in the No- 

 thodectes zone is Zanyderis, a bat showing affinities 

 with the vampires (Phyllostomatidae) of South 

 America. 



The NotTiodedes zone ("Tiffany" and "Clark Fork") 

 is basal Eocene, as indicated by the absence of the 

 four orders Primates, Perissodactyla, Artiodactyla, 

 Rodentia; it is lower Eocene, as indicated by the 

 presence of Phenacodus and Coryphodon. 



The mammalian life of the "Clark Fork" beds in 

 the Big Horn Basin of Wyoming, to the north, is very 

 similar (Granger, 1914.1, p. 204) to that of the "Tif- 

 fany beds" in Colorado. These "Clark Fork beds," 

 500 feet in thickness, are characterized by the pre- 

 dominance of the Condylarthra (PJienacodus and Ec- 

 tocion), remains of which constitute three-fourths of 

 the fossils collected from them. The amblypod un- 

 gulates are represented by CorypJiodon and by the 

 first appearance of an animal (Eohathyopsis) ancestral 

 to Baihyopsis, of the Wind River formation, which in 

 turn is ancestral to the horned UintatJierium of the 

 Bridger formation. Among the Reptilia is the last 

 surviving Champsosaurus from the Fort Union and 

 the Cretaceous, a distinctively basal Eocene type. 



EARLY EOCENE TIME 



General correlation. — Lower Eocene (Wasatch) time 

 began, it may be said, with the first appearance of 

 Coryphodon and Phenacodus in the "Clark Fork" and 

 "Tiffany beds" described above as the Phenacodus- 

 Nothodectes- Coryphodon zone, in which is found the first 

 phase of the Coryphodon fauna. The modernization 

 occurred later, in the "Sand Coulee beds" (Eohippus 

 zone), which overlie the "Clark Fork." 



The Sparnacian of Europe is broadly parallel with 

 part of the Wasatch formation {Coryphodon zone) of 

 America. It is typified in France by the deposits of 

 Soissons, Meudon, and Vaugirard; in England by the 

 Woolwich beds, which contain a rich flora. In these 

 fluviomarine, lagoon, and lacustrine deposits of Europe 

 mammals are rare, and homotaxis with America is 



afforded through the large coryphodons, the perisso- 

 dactyl Lophiodon, and the creodonts Palaeonictis and 

 Pachyaena. This sparse European fauna, which in its 

 early stages lacks Equidae (Hyracotherium) , has almost 

 a counterpart in that of the Nothodectes zone of the 

 Rocky Mountain region. 



The two upper zones of the lower Eocene (Wasatch) 

 are correlated with the Ypresian of Europe. 



Wasatch and Sparnacian floras. — According to Berry 

 (1914.1, p. 148) the earliest Eocene beds of Europe 

 (Sparnacian and Ypresian stages) contain the flora 

 found in the Oldhaven, Woolwich, and Red beds of 

 England, largely unstudied, and the small flora from 

 the Paris Basin recently described. The Woolwich 

 beds have yielded the fig (Ficus), the locust (JRohinia), 

 the tulip tree (Liriodendron) , and Grevillea, a pro- 

 teaceous plant now confined to Australia. Berry 

 believes (letter to the author, April 1, 1918) that in 

 lower Wasatch time the Fort Union flora persisted over 

 the Rocky Mountain basin region. This belief implies 

 that the climate was then prevailingly warm-temperate 

 but that there were occasional incursions of trees of 

 subtropical type. 



Sedimentation during Wasatch time. — As the Sparna- 

 cian stage of Europe, which is equivalent to part of the 

 Wasatch, derives its name from Epernay (Latin Spar- 

 nacum), so the Wasatch stage of mammalian life 

 derives its name from the typical Wasatch group of 

 Hayden in western Wyoming, a single mammal-bearing 

 member of which is the Knight formation (Veatch, 

 1907.1), 1,750 feet in thickness, containing Cope's 

 types of Eohippus index, E. vasacciensis, Phenacodus 

 primaevus, Coryphodon radians, C. semicinctus, C. 

 latipes. These species of mammals do not represent 

 the oldest Wasatch fauna; they are of the same age as 

 the species found at the "Lysite" horizon (life zone 

 No. 8) of the Big Horn Basin. 



Among the chief sources of Wasatch mammals are 

 the following: 



Feet 



1. Knight formation (Veatch), top of typical Wasatch 



group (Hayden), southwestern Wyoming; red and 

 yellow sandy clays 1,750 



2. Wasatch formation, Big Horn Basin, Wye; red, 



brown, and gray sandstones and clays 2, 025 



3. Wasatch formation ("Bitter Creek" of Powell and 



"Vermilion Creek" of King), Washakie Basin, 

 Wyo.; red and gray clays and sandstones 4, 000-5, 500 



4. Wasatch formation of the San Juan Basin, N. 



Mex 1,500 



5. Wasatch formation of the Uinta Basin, Utah (White, 



1878) 2,000 



6. Wasatch formation of the Powder River Basin, Pump- 



kin Buttes, Wyo 2,400 



The estimate made by King (1878.1) of the thick- 

 ness of the sediments in the Washakie Basin (4,000- 

 5,500 feet) is considered high (Granger). It is inter- 

 esting to note that the mean thickness (about 2,300 

 feet) of the Wasatch sediments in the six areas listed 

 above exceeds somewhat that of the Bridger formation 

 (1,875 feet). 



