CHAPTER VIII 



THE SUBCLASS ANAPSIDA 



Temporal region of skull wholly roofed over, or secondarily emargi- 

 nated from the sides, not perforated. 



1. ORDER COTYLOSAURIA 



Temporal roof complete, not emarginated: skeleton primitive. An 

 order of reptiles, not only the oldest geologically, but more primitive 

 in structure than any other; probably the ancestral stock of all later 

 Amniota. They were very variable in size, structure, and habits: 

 as known, subaquatic, lowland, or marsh reptiles, never cursorial or 

 chmbing; invertebrate feeders for the most part, varying in size from 

 less than one to about ten feet in length. The body was never slen- 

 der, nor the legs long; the neck was always short. Dermal ossifica- 

 tions of any kind are known in but a few genera, Diadectes, Pantylus, 

 and the Pariasauridae; the body was probably covered with horny 

 plates or scales. The earliest known member of the order dates from 

 the Middle Pennsylvanian, the latest from the Middle Triassic. 



None has all the primitive characters given in the Hst, but the 

 losses or modifications in any form are few. They may be discussed 

 under three groups, which include their chief evolutional modifica- 

 tions. 



I. Carboniferous and Lower Permian 



The intertemporal bone and the otic notch are known in but one or 

 two genera, the Seymouriidae ; the supratemporals are absent in the 

 Captorhinidae, the tabulars also in Labidosaurus. The ectopterygoid 

 has not yet been certainly demonstrated in any genus, though prob- 

 ably present. The parietal foramen is absent in Pantylus, and pos- 

 sibly also in some others. Free ribs are present to the sacrum and in 

 the tail in Seymouria only, absent wholly in the lumbar region of the 

 Captorhinidae. Parasternal ribs are known only in the last-named 

 family and Sauravus. Two pairs of sacral ribs are present in all 

 genera except Seymouria and Diadectoides . There are from twenty- 

 two or twenty-three to twenty-six presacral vertebrae; the tail of 



