MATTHEW, CLIMATE AND EVOLUTION 261 



specialized edentate types. The Tseniodonta range from Paleocene to 

 Upper Eocene in North America and are doubtfully recorded in the 

 early Eocene of Europe. They may be hypothetically regarded as a 

 Cretaceous-Eocene ancestral group in the northern world, from whose 

 early members budded otf the ancestral Xenarthra in the Nearctic, pos- 

 sibly also the Pholidota and Tubulidentata in the Pal^arctic, the whole 

 group being driven southward at the beginning of the Tertiary, except 

 for a few lingering remnants, rare and little known. Of these lingerers, 

 we may instance in the (Bridger) mid-Eocene of Wyoming Metacheir- 

 omys, whose affinities are distinctly armadilloid and an unnamed but 

 more primitive genus in the Lower Eocene of AYyoming approximately 

 ancestral to it ; "Lutra" franconica of the Oligocene of Germany, shown 

 by Schlosser to be related to the Aardvark, Pahromanis and Orycteropus 

 of the Miocene of Samos, and more doubtfully PaJrcorycteropiis and 

 Necrodasypus (in part) of the Oligocene of France. 



Whether the rare gi-ound-sloth remains from the (?) Middle Miocene'^- 

 and Lower Pliocene of the western United States are to be regarded as 

 surviving Northern edentates or as immigrants from the south is not 

 certain, but the latter explanation is more probable. 



The Old World edentate groups, although still surviving in Ethiopia 

 (Manis, Orycteropus) and the East Indies (Manis), are not known to 

 have undergone any considerable expansion during the isolation-period 

 of the early Tertiary.'^^ The Xenarthra, on the other hand, are first 

 represented in the early Tertiary of South America by armadilloid forms 

 and they blossomed out in the isolated continental conditions that pre- 

 vailed during the Tertiary in that continent into a wide range and 

 diversity of type, just as the Condylarthra appear to have done under 

 the same conditions there and the marsupials in Australia. Of the five 

 principal groups — tree-sloths, ground-sloths, anteaters, armadillos and 

 glyptodonts — only the second, fourth and fifth are known as fossils, and 

 only the first, third and fourth have survived. The fossil groups reached 

 their maximum of size and specialization in the Pleistocene, and rein- 

 vaded North America in the Pliocene and Pleistocene (possibly earlier, 



'2 There is some question as to thie true liorizon of thie ground-slotli claw found by 

 Sinclair in the Mascall formation (Middle Miocene) of Oregon. The specimen may have 

 washed down from the overlying Rattlesnake Beds. Lower Pliocene [oral communication 

 from J. C. Merriam]. 



'^ But this may be due only to the imperfection of the geologic record. We know 

 nothing of the early Tertiary faunae of the Ethiopian and Oriental regions, save for the 

 Oligocene of Egypt. The Eocene faunne of South Africa, India and the East Indies may 

 have included a considerable expansion of pholidate or tubulidentate mammals, corre- 

 sponding to the xenarthral expansion of the New World, but earlier extinguished because 

 of the earlier invasion of those regions from the north. 



