DEVELOPMENT OF VERTEBRATE LIFE IN PERMO-CARBONIFEROUS 269 



As the change which affected the environment of the upper Penn- 

 sylvanian fauna was an elevation and exposure of the land with little 

 deposition the record of the life change, in preserved fossils, is very imperfect, 

 the continued sinking of the land in the eastern part of the Southern Sub- 

 province maintained the old conditions and archaic types of life in the area 

 best explored and has given a false impression of the general state of affairs. 

 The record there preserved is of a relict fauna, while the record of the ad- 

 vancing development in progress on the higher lands is not preserved or has 

 not yet been discovered. Matthew, in his essay upon climate and evolution, 

 has given his ideas of the effect of such a change as occurred in late Penn- 

 sylvanian time:^ 



"The periods of continental emergence were periods of arid and markedly 

 zonal climate, and the faunae must adapt themselves to these conditions. Such 

 conditions, while favoring the spread and wide distribution of races, would be 

 unfavorable to abundance of life and the ease with which animals could obtain a 

 living. The animals subjected to them must maintain themselves against the 

 inclemency of nature, the scarcity of food, the variations of temperature, as well 

 as against the competition of rivals and the attacks of enemies. In the moist 

 tropical climatic phase, animals would find food abundant and temperature rela- 

 tively constant; but the larger percentage of carbonic acid and probably smaller 

 percentage of oxygen in the atmosphere during those phases would tend to slug- 

 gishness. 



"We should expect, therefore, to find in the land life adapted to the arid 

 climatic phase a greater activity and higher development of life, special adapta- 

 tions to resist violent changes in temperature and specializations fitting them 

 to the open grassy plains and desert life. In the moist tropical phase of land 

 life, we should expect to find adaptations to abundant food, to relatively sluggish 

 life, and to the great expanse of swamp and forest vegetation that should 

 characterize such a phase of climate." 



While these remarks are largely applicable to the mammals with which 

 Dr. Matthew is chiefly concerned in his essay, similar effects would doubtless 

 be produced in lower forms of life. 



The place of origin of the Permo-Carboniferous fauna is unknown. As 

 shown previously there are reasons for considering that the North Amer- 

 ican radiation of the Permo-Carboniferous fauna started in the eastern 

 part of the continent, but this is far from proven. Until more detailed 

 work shall establish the true relations of North America to the other con- 

 tinents of late Paleozoic time the question may not be settled. The 

 question of the origin of the fauna and its relations to the somewhat similar 

 fauna of South Africa is discussed in a preliminary way elsewhere (Carnegie 

 Inst. Wash. Pub. No. 207, p. 117). It is the opinion of the author that 

 the North American fauna was unique in its adaptations and radiation 

 and that the presence of such highly specialized forms as Edaphosaurus in 

 Saxony and Bohemia was due to later migrations. This opinion may very 



1 Matthew, W. D., Climate and Evolution, Annals N. Y. Acad. Sci., vol. xxiv, p. 177, 1915- 



