1 54 THE PERMO-CARBONIFEROUS RED BEDS OF 



of the African and North American faunas were developed, and that there 

 was a dispersal of the fauna from a common center. Broom says:" 



' ' Taking all the facts into consideration, it seems to me probable that in Upper 

 Carboniferous times there appeared in the northern part of South America a primitive 

 land vertebrate fauna, comprising among other types temnospondylous amphibians, 

 primitive cotylosaurians, and primitive ancestral Pelycosaurs. Before the conclusion 

 of the Carboniferous period, this South American fauna invaded North America, and 

 almost immediately afterwards the northern group became isolated. The isolation 

 continued during at least the whole of the Lower Permian times, and these isolated 

 types became greatly specialized in their struggle with some adverse conditions. 

 What the conditions were we do not know, and no satisfactory explanation has, I 

 think, been given of the development of the enormous spines of the vertebrae in the 

 Pelycosaurs. Nor do we know what caused the extinction of the whole fauna about 

 the Middle Permian times, but most likely some change in climatic conditions. 



"In South Africa the first Karroo reptile to appear is Mesosaurus, which is 

 found in beds a little above the Dwyka tillite. It is certainly generically similar to 

 the Mesosaurus of Brazil, and closely allied specifically. This occurrence of Meso- 

 saurus on both sides of the Atlantic, as well as a series of plants which are specifically 

 identical in Brazil and South Africa, renders it practically certain that there was a 

 land connection between South America and South Africa in Lower Permian times, 

 and that animals might have migrated from what is now the one continent to the 

 other. There is, however, no evidence that any reptiles other then Mesosaurus 

 arrived in South Africa till some considerable time after the origin of the Permian. 

 Perhaps the reason for this may be that about the beginning of the Permian period 

 South Africa, and probably much of South America, Australia, and India were, 

 from some cause or other, largely covered by glaciers, and possibly for long afterward 

 the climate was too severe to allow the more northern or equatorial types to invade 

 the south. In beds which are called Ecca we get the eariiest immigrants — a large 

 carnivorous reptile called Archeosuchus, which may have been a dinocephaHan, and 

 evidence from a tooth of a large undoubted dinocephaHan which was a herbivore. 

 It is, however, not till Middle Permian times that the fauna becomes rich. Then 

 there appear pareiasaurians, a considerable variety of dinocephalians, many thero- 

 cephaHans, a few anomodonts, the only known dromasaurians, and a temnospondy- 

 lous amphibian. Where this great collection of forms came from is, of course, un- 

 known. They can hardly have originated in South Africa, because though the lower 

 Permian beds are Kthologically exactly similar to those of later Karoo times, they 

 are almost entirely unfossiliferous. 



"It seems to me, however, probable from the general resemblance of the African 

 fauna to the North American Permian, that both have come from the common 

 source, which I believe must have Hved in the northern part of South America. 

 After the invasion of North America in Upper Carboniferous times, all connection 

 between North and South America ceased for a very long period. The near relatives 

 of the ancestors of the North American Permian forms left in South America evolved 

 on quite other Hues. For long they were probably confined to the BraziHan region, 

 owing to the cold prevailing in the South, but ultimately they spread down and 

 across the South Atlantic into Africa, where they for the most part arrived during 

 the Middle Permian times." 



If such a connection, as supposed by Broom, existed between North and 

 South Americ a, it must have been in or before Pennsylvanian time. Deposits 



" Broom, Bull. Amer. Mus. Nat. Hist., vol. xxviii, art. xx, p. 233, 1910. 



