PHYLOGENY AND CLASSIFICATION OF REPTILES 419 



Protorosaurus must represent an entirely new order of reptiles, 

 which very properly may be associated with the Ichthyosauria in 

 the division I call the Parapsida. It might be urged that the 

 Diapsida originated from such a type by the development of a 

 lower vacuity after the upper one had been evolved. The argu- 

 ments against this view are too many and too potent; I need not 

 repeat them. 



Admitting three chief groups of reptiles arising in late Penn- 

 sylvanian or early Permian times, we have yet another, one which 

 by general consent is ancestral to all later amniota, the Coty- 

 losauria, and their direct descendants the Chelonia. 



Fig. 5. — Pantylus, skull, from side, three-fourths natural size. Anapsida 

 Permocarbonif erous . 



In this group the temporal region of the skull is wholly imper- 

 forate, and for the most part completely roofed over, a group which 

 very properly may be called the Anapsida. It was Baur who first 

 asserted that the turtles could not have originated from reptiles 

 with a perforated temporal region. Cope derived the order directly 

 from the Cotylosauria, through the Chelydosauria, an order based 

 upon a misapprehension. I approved and emphasized Baur's 

 views in 1904. Case and Hay both hold the same opinion, and 

 only recently Watson has forcibly and convincingly presented the 

 claims of Eunotosaurus, from the Permian, as a real connecting 

 link between the two orders. And Broom and others are of the 

 same opinion. This unanimity of opinion renders further discus- 

 sion superfluous; Watson has presented the arguments. 



We have, then, at least four main divisions or subclasses of the 

 class Reptilia, all beginning in Paleozoic times, and all represented 



