Il8 THE PERMO-CARBONIFEROUS RED BEDS OF 



Broom says, in the Bulletin of the American Musevim of Natural History 

 for 1910, page 228: 



"Though it is many years since Cope first caHed attention to the resemblance 

 between some of the American and African types, of later years zoologists have been 

 more impressed by the difTerences. Like most others, I had regarded the resemblances 

 as more due to a parallel development than to afhnity, and I was a little surprised to 

 find that the resemblances were of a more fundamental nature than had been sup- 

 posed. Not only do certain American tyj^es resemble, somewhat remotely, of course, 

 African forms, but the whole fauna has got an African look about it that is very 

 striking. Williston regards the American Permian reptiles as belonging to three 

 groups: the Pelycosaurs, the Cotylosaurs proper, and the Pariotichus group; and it 

 certainly is very remarkable that some years ago, writing of the reptiles of South 

 Africa, I placed them in the groups Procolophonia, ParciasaHria, Thcrocephalia, 

 Anomodoutia, and Cynodontia. If we unite the alhed mammal-like groups, Thcro- 

 cephalia and Anomodontia, under the Therapsida, and omit the Triassic Cynodontia, 

 we get our principal Permian reptiles also in three groups, and, further, the three 

 groups correspond in many ways to the American. The Pelycosaurs resemble the 

 Therapsida; the Cotylosaurs the African Pareiasauria, and the Pariotichus group 

 the Procolophonia. ' ' 



And further, on pages 230 and 231 : 



"From these points of comparison I think one must conclude that the Pelyco- 

 sauria are allied to the Therapsida. In some respects the former are more specialized, 

 but in most they are more primitive. The skull, while essentially similar in the two 

 types, is more primitive in the Pelycosauria than the Thcrocephalia in the retention 

 of the quadrato-jugal and perhaps of a post-parietal and post-temporal. It is less 

 primitive in the loss of the transpalatine. The Dinocephalia, alone among the 

 Therapsida, retain the primitive quadrato-jugal. The Dromasauria alone have the 

 primitive character of the lachrymal meeting the septo-maxillary, a character also 

 seen in Edaphosaurus, and the possession of abdominal ribs, also present in some 

 Pelycosavirs. 



"In retaining the typical Diapsidan digital formula the Pelycosauria is more 

 primitive, but though the Therapsida have acquired the mammalian formula of 

 2, 3, 3, 3, 3, to suit the placing of the feet under the body, and to bring the toes into 

 line, we can see from the condition of the metatarsals and metacarpals in the 

 Dromasauria that this formula has probably only been recently acquired, and that 

 the feet are not yet completely suited to the new mode of walking. 



"The conclusion to which I come is that the Pelycosaurs and Therapsida had 

 a common ancestor in the Upper Carboniferous times, which was characterized by 

 having the typical Diapsidan digital formula, abdominal ribs, a single temporal 

 fossa, a quadrato-jugal bone, and a Rhynchocephalian palate. Such an ancestor 

 could be so near the ancestral Rhynchocephalia or Diaptosauria that, though it had 

 only a single temporal fossa corresponding to the lower one in Sphcnodon, it ought 

 to be regarded as a Diaptosaurian, and though the Pelycosauria are speciaHzed in 

 a number of respects, I should still keep them in the Diaptosauria. 



"The South African Therapsidans have sprung from the same ancestor, but 

 have developed in a different way. By a change of habit the Hmbs have become 

 more powerful, and by the adoption of the habit of walking with the body off the 

 ground the digital formula has been changed from 2, 3, 4, 5, 3 to 2, 3, 3, 3, 3. 

 The changes in the skull are of less importance, the only marked one being the loss 

 of the quadrato-jugal. The Dromasauria are perhaps quite as near to the common 



