HASEMAN, GEOGRAPHICAL DISTBIB VTION IN SOUTH AMEBIC A 97 



sence of Permian and Triassic South African land reptiles from South 

 America indicates that Scaplionyx evolved from some northern ancestor 

 from which Erythrosnchus also descended. 



Broom and others have attempted to show that the Permian reptiles 

 of South Africa and Texas are related. There appears to be no doubt 

 that these reptiles are related, but there is still very diverse opinion as to 

 how nearly they are related. In the conclusion of this interesting paper, 

 Broom suggests a possible scheme of distribution of the Permian reptiles. 

 He thinks that it is probable that a Lower Carboniferous land vertebrate 

 fauna existed in northern South America. This primitive vertebrate 

 fauna included among other forms temnospondylous amphibians, primi- 

 tive cotylosaurians and primitive ancestral pelycosaurs. He presumes 

 that this fauna ultimately migrated on one hand to North America and 

 on the other hand over the Gondwana Land to Africa. In order to 

 obviate the absence of all early Permian reptiles in South Africa except- 

 ing Mesosaurus, he further presumes that Permian glaciers of Brazil 

 prevented the other primitive reptiles from reaching Africa until middle 

 and late Permian. 



The above view is possible, but not probable, because it is based on 

 the following assumptions: (a) a continuous Gondwana Land; (&) the 

 existence of lower to middle Permian glaciers in the region of the alleged 

 trans-Atlantic Gondwana, and not in region of northern South America, 

 which was with all probability the highest point at that epoch, and (c) 

 the existence of primitive Carboniferous reptiles and temnospondylous 

 amphibians which are not known from South America. We conclude, 

 therefore, that there is little or no evidence in favor of the exchange of 

 Permian reptiles between South America and Africa by way of a con- 

 tinuous Gondwana Land. 



In view of all this, the only suggestion which appears to agree with 

 the known facts of geology, paleontology and the Permian environmental 

 complexes is that the primitive Carboniferous reptiles, from which the 

 Permian fauna evolved, originated in the northern hemisphere and were 

 pushed south from Eurasia into Africa, where the descendants retained 

 certain primitive characters and evolved along similar lines in such a 

 way that they more or less remotely resemble the descendants from the 

 same primitive stock which lived in Texas. Mesosaurus is an aquatic 

 and at least semi-marine form, and does not lend any positive support 

 to a Permian connection between Africa and South America, 44 because 



44 The distribution of the extinct and living side-necked turtles (Pleurodira) offer 

 another case of the same principle. The pleurodirans are now found only in the southern 

 hemisphere, but they were very abundant in the Cretaceous of the northern hemisphere, 

 where they probably already existed in the Jurassic. The two other groups of "shelled 

 turtles" (Cryptodira and Trionychoidea) also fit into the scheme of a northern origin 

 and distribution of land animals. 



