CHAPTER VII 



ANOMODONTIA 



LYSTROSAURUS 



Over a large area of South Africa, chiefly along the Orange 

 River and its tributaries, there is an extensive series of deposits 

 many hundreds of feet in thickness, usually called the Karoo beds, 

 which, for more than fifty years, have been widely famous among 

 scientific men for the many and remarkable vertebrate fossils 

 which they have yielded. These deposits seem to represent the 

 whole of the vast interval of time from the Carboniferous to the 

 Jurassic, that is, the whole of the Permian and Triassic, though 

 not many fossils have been found in the lowermost strata. Among 

 the fossils of the lower strata are those of the strange creatures 

 described in the following pages as Mesosaurus. From the deposits 

 representing the Upper Permian and the Triassic the fossils that 

 have been obtained are both abundant and diverse. Unfortu- 

 nately, however, of the scores of forms that have been discovered 

 few are known completely, and still fewer are known sufficiently 

 well to enable us to picture the living animals. 



From the Upper Permian Karoo rocks two orders of reptiles 

 have been recognized, the Cotylosauria, represented by more 

 specialized forms than those from the Lower Permian of North 

 America; and the order or group called by Broom the Therapsida. 

 While the forms of this latter group have certain definite structural 

 relationships with each other, they show so great a diversity among 

 themselves that, when they shall be better known, it will be 

 found necessary perhaps to separate them into several distinct 

 orders. 



At least five groups of the Therapsida are now recognized by 

 Broom, the Dromasauria, Dinocephalia, Anomodontia, Thero- 

 cephalia, and Theriodontia. Of all these the members of the 

 last-mentioned group have attracted the greatest interest among 



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