THE SKULL OF REPTILES 



21 



-4A 



with the prevomers is lost in some Cynodontia (Fig. 43 c) and 

 Rhiptoglossa. Teeth are generally present in the Theromorpha, 

 Rhynchocephalia, and Squamata, and in some Therapsida and 

 ''Pseudosuchia." In the early reptiles (Figs. 6, 21, 24 c, 40 c) they 

 are more or less loosely articulated with the basipterygoid process of 

 the basisphenoid, as in most modern reptiles, but are fixed in the 

 Therapsida (Fig. 43 c) and not a few others. There is an interptery- 

 goidal space between them partly filled with the parasphenoid ros- 

 trum in the early reptiles (Figs. 6, 21 a), as in the Plesiosauria (Fig. 

 47 f), Rhynchocephalia, most Squamata (Fig. 55 c), etc. In some 

 Therapsida (Fig. 43 c), Notho- 

 sauria (Fig. 47 e), Placodontia 

 (Fig. 49 b), they unite along the 

 whole middle line. There is a 

 theory that the pterygoids are 

 the real homologues of the mam- 

 malian alisphenoids.^ 



Ecto pterygoids (ec). The ecto- 

 pterygoids (transpalatines) have 

 not yet been certainly demon- 

 strated in the early Cotylosauria, 

 though perhaps present; they are 

 certainly absent in some of the 

 Temnospondyli. They have been 

 recognized in all other orders ex- 

 cept the Ichthyosauria and Chelonia, connecting the pterygoids with 

 the posterior end of the maxillae, back of the palatines; sometimes 

 also with the jugals in the Squamata (Fig. 55 c). Most remarkable 

 are their relations in Pteranodon (Fig. 72 c) of the Pterosauria, where 

 they pass above the palatines to unite with the pterygoid. The 

 ectopterygoids are believed by some to be the homologues of the 

 pterygoid process of the alisphenoid of the mammals. 



Epi pterygoids (ep). A pair of bones articulating below with the 

 pterygoids, above with the parietals (Fig. 8). They have been ob- 

 served in the Temnospondyli, various genera of the Cotylosauria, 

 Theromorpha, and Therapsida, and are probably generally present 

 in reptiles, though absent in the Crocodilia, many Chelonia, the 



Fig. 7. Pantylus. Cotylosaur skull: 

 left quadrate region, with section of 

 mandible through condyle. En- 

 larged one half. 



' [Watson has shown that this view is untenable. — Ed.] 



