PHYLOGENY AND CLASSIFICATION OF REPTILES 417 



ichthyosaurs had an independent origin from the Cotylosauria, and 

 so indicated in a phylogenetic diagram. Broom adopted this 

 view in 1901. In 1904 I quoted Cope's views with approval. 

 More recently von Huene has reached the same conclusion, finding 

 in the Proganosauria or Mesosauria, as here accepted, either the 

 ancestral stock or one closely allied to it. Baur, it is true, in 1887 

 considered the Proganosauria as the ancestral stock of the ichthy- 

 osaurs, but Baur's Proganosauria later included Paleohatteria, 

 believed to be a double-arched reptile. Merriam accepted the 

 Cotylosaurian ancestry, and Sollas very recently has voiced his 

 approval. 1 Indeed, the opinions now seem to be unanimous and 

 further discussion is superfluous. 



Fig. 4. — Araeoscelis, skull, from side {A ) , and above (23) , natural size. Parapsida 

 Permocarboniferous. 



No order of reptiles has been the subject of more dispute than 

 the Squamata. The apparent absence of the quadratojugal, and 

 the presence of an additional bone in the upper temporal region, 

 together with the freely movable quadrate, have been explained 

 in various ways. At one time the arch articulating with the 

 proximal end of the quadrate was considered the lower one, and 

 the two bones the squamosal and quadratojugal. Again, the 



1 Sollas makes a rather curious error in saying that I was prepared to accept 

 the view, with certain reservations, of the direct descent of the ichthyosaurs from the 

 Stegocephalia. What I said was that the two bones in the temporal region of the 

 ichthyosaurs point to a direct origin from the stegocrotaphous reptiles. 



