64 



TITANOTHEEES OF ANCIENT "WYOMING, DAKOTA, AND NEBRASKA 



washed into the streams during heavy rains and 

 scattered by the action of crocodiles, carnivores, tur- 

 tles, and fish. Other skeletons show traces of gnaw- 

 ing, probably by small Ptilodontidae, which proves 

 that many of the bones lay for some time on the surface 

 of the ground before reaching the streams or being 

 covered in flood time by water-borne sediments. 



ZONES 3 AND 4: DEITATHERIUM AND PANTOLAMBDA ZONES 

 [Torrejon and Fort Union faunas; in part Thanetian of Europe] 



The mammals of the Torrejon formation of north- 

 western New Mexico, whose remains are found in a 

 stratum about 250 feet above the base of the Puerco 

 mammal-bearing level, are somewhat larger, con- 

 siderably more diversified (perhaps because more fully 

 known), and of slightly more progressive type. They 

 show very close affinity to the Fort Union mammals of 

 Montana and some affinity to the Cernaysian forms 

 discovered in the conglomerat de Cernay, near Rheims, 

 France. 



The multituberculates, which occur in the Holarctic 

 region in upper Triassic (Rhaetic) time, now make 

 their last appearance abundantly; of the Ptilodonti- 

 dae, Ptilodus (or Neoplagiaulax) is found in New 

 Mexico, Montana, and Cernay; the large Polymasto- 

 don that distinguishes the upper Puerco zone does 

 not recur. 



Here also are five families of archaic carnivores 

 (Creodonta), among which, in the Miacidae, there is a 

 genus (Didymidis) which appears to lead through the 

 civet and doglike forms of the lower and middle 

 Eocene into forms related to the modern Carnivora. 

 Among the three Torrejon families of Insectivora the 

 existing Centetidae (tenrecs) are possibly related to 

 the genus Palaeorydes , a very primitive form resem- 

 bling the modern Cape golden moles {(JhrysocMoris of 

 South Africa, Necrolestes of South America). The 

 ancestors of the modern edentates are highly diversi- 

 fied (Edentata, Ganodonta) and include slothlike 

 animals, indicative of present or former migrations 

 into South America. Of the families of archaic ungu- 

 lates two (Phenacodontidae and Mioclaenidae) repre- 

 sent the Condylarthra, and two (Periptychidae and 

 Pantolambdidae) represent the Amblypoda. Of the 

 Amblypoda Pantolambda cavirictus, which is also 

 found in the Fort Union, is very characteristic. Of 

 the bearlike Creodonta (Arctocyonidae) Claenodon 

 ferox, which is closely related to the Arctocyon of the 

 Thanetian of France, occurs also in the Fort Union 

 of Montana. 



Most of these mammals of the Torrejon, like those 

 of the Puerco, were ancient adaptive radiations of 

 the Mammalia. They were small-brained, had de- 

 fective foot structure, and were unfitted to compete 

 with the ancestors of the modernized mammals, 

 which begin to appear immediately above the Noiho- 

 dedes zone. Six families approached extinction at the 



end of the Torrejon — the Plagiaulacidae of the Multi- 

 tuberculata; the Oxyclaenidae of the Carnivora; the 

 Conoryctidae of the Edentata; the Periptychidae and 

 Pantolambdidae of the Ambyploda (which, however, 

 are related to the succeeding coryphodons) ; and the 

 Mioclaenidae of the Condylarthra. The Plagiaula- 

 cidae and Oxyclaenidae, however, survive into the 

 early Wasatch, the Periptychidae into the "Tiffany 

 beds." Torrejon time thus ends with the extinction 

 of a large number of families of archaic mammals, 

 though several families survived, passing into the 

 succeeding lower Eocene. 



Unconformities of the Torrejon with the underlying 

 Puerco have not been found. (Sinclair and Granger, 

 1914.1, p. 312; also Gardner, 1910.1, p. 722, and Bauer, 

 1916.1, pp. 273-277.) There is no doubt about the 

 aqueous origin of either the Puerco or the Torrejon 

 deposits. The Torrejon carries less petrified wood 

 than the Puerco, but it contains Z7mo-bearing beds, 

 which occur repeatedly in the gray clays, and abundant 

 shells of land moUusks {Pupa), which are found in the 

 clays that contain bones of mammals. Lithologically, 

 the Torrejon closely resembles the Puerco, except that 

 gravels of quartzite, jasper, red shale, etc., occur in 

 some of the channel sandstones. Mammals appear 

 principally in the zones filled with small rusty calca- 

 reous concretions, which occur in clays that range in 

 color from red mottled with green to gray. The upper 

 boundary of the Torrejon is everywhere marked by 

 the presence of Tetradaenodon (ancestor of PJiena- 

 codus) and of the two amblypods PeriptycTius rhabdo- 

 don and Pantolambda. The total thickness of the 

 Torrejon differs at different places, ranging from 240 

 to 660 feet, whereas the approximately contempora- 

 neous Fort Union of Montana, which possibly also 

 represents the Puerco, attains a thickness recorded as 

 nearly 6,000 feet. 



The top of the Tori'ejon is in unconformable contact 

 with sandstone that indicates a cycle of deposition of 

 coarse sediments and alluvial fans, attributed to 

 Wasatch time. 



SECOND FAUNAI PHASE (LOWER EOCENE) 



TRANSITIONAL BASAL EOCENE FAUNAS 



ZONE 5; PHENACODUS-NOTHODECTES-COETPHODON ZONE 



[Base of Wasatch formation of Big Horn Basin, first Wasatch life zone, Big Horn 

 A; Cernaysian of Europe] 



The first Wasatch life zone is represented in the 

 "Tiffany beds" of southwestern Colorado, in the basal 

 part of the Wasatch formation (horizon Big Horn 

 A= "Clark Fork") of the Big Horn Basin, Wyo., and 

 probably in the summit of the Fort Union formation 

 of Montana. In southwestern Colorado, near the 

 headwaters of the San Juan, are the "Tiffany beds" 

 of Granger, which contain a fauna characterized by 

 the last appearance of PeriptycTius and by the first 

 appearance of Phenacodus and of Coryphodon, a genus 



