SQUAMATA 



155 



The tail was long, no longer than the tail of some land lizards, 

 but more powerful, and broader and flatter. It was expanded or 



Fig. 72. — Skulls of mosasaurs. Upper figure, Clldastes, from the side; middle 

 figure, Platecarpus, from below; lower figure, Tylosaurus, from above: an, angular; 

 bs, basisphenoid; c, coronoid; ep, epipterygoid; fr, frontal; j, jugal; /, lacrimal; m, 

 maxilla; na, nasal; oc, occipital condyle; pa, parietal, palatine; pm, premaxilla; 

 pf, prefrontal; pt, pterygoid; po, postorbital; q, quadrate; sp, splenial; sq, squa- 

 mosal; tr, transverse; v, vomer. 



dilated more or less toward the free end, that is, with the beginning 

 of a terminal caudal fin, such as the more specialized ichthyosaurs 

 and crocodiles possessed. The vertebrae were procoelous, that is, 



