CLASSIFICATION OF REPTILES 17 



Order SAUROPTERYGIA 



Aquatic reptiles with a single temporal vacuity; no supratemporal bone, 

 or quadratojugal; ribs single-headed, diapophysial; coracoids large, meet- 

 ing in middle line, single; neck long, tail short. 



Suborder Nothosauria Triassic, Europe. 



Plesiosauria Triassic to close of Cretaceous, cosmopolitan. 



*Order PROGANOSAURIA 



Primitive aquatic reptiles; single (? upper) temporal perforation; neck 

 elongate; nares posterior; vertebrae notochordal; intercentra persistent; 

 pelvis plate-like; phalangeal formula 2, 3, 4, 5, 4(6). Permocarboniferous, 

 Africa, South America. 



Order ICHTHYOSAURIA 



Reptiles with all aquatic adaptations; a single, upper temporal perfora- 

 tion; both supratemporal and squamosal present; a single coracoid. 

 Middle Triassic to Benton Cretaceous, cosmopolitan. 



*Order PROTOROSAURIA 



A single, upper temporal vacuity, quadrate fixed (neck vertebrae elongate) ; 

 bones hollow; cervical ribs single-headed, articulating with centrum; 

 pelvis plate-like. Permian, North America, Europe. 



Order SQUAMATA 



A single, upper temporal vacuity, or, secondarily none; quadrate loosely 

 articulated with cranium; teeth on palate; intercentra more or less per- 

 sistent; a single coracoid; ribs single-headed, central. 



Suborder Lacertilia Trias to recent. 



Mosasauria Upper Cretaceous, cosmopolitan. 

 Ophidia Upper Cretaceous to recent. 



*Order THALATTOSAURIA 



Aquatic reptiles; two (?) temporal vacuities; ribs single-headed, attached 

 to centrum; single coracoid; no intercentra. Trias, California. 



Order RHYNCHOCEPHALIA 



Two temporal vacuities on each side; palate with teeth; intercentra 

 persistent; a single coracoid; teeth acrodont; ribs articulating with 

 centrum and arch. 



Suborder Rhynchosauria Triassic, Europe. 

 Sphenodontia Triassic to recent. 



Choristodera Uppermost Cretaceous, lowermost Eocene, 

 North America, Europe. 



