A SYNOPTIC CLASSIFICATION OF THE REPTILIA 211 



II. SYNAPSIDA. A single temporal opening, primitively below the 

 poslorbito-squamosal arch; two coracoids. 



4. Theromorpha. Skeleton primitive; vertebrae notochordal with 

 persistent dorsal intercentra; teeth on palate bones; phalangeal 

 formula primitive; propodials horizontal in locomotion. 



A. Pelycosauria. Carnivorous; teeth strongly anisodont 

 with diastema; dorsal spines more or less elongated; inter- 

 parietal and tabulars present. Lower Permian. 



B. Edaphosaiiria. Malacophagous; teeth small, isodont. 

 Dorsal spines elongate, with bars; interparietal and tabulars 

 present. Lower Permian. 



C. PoLiosAURiA. Insectivorous; teeth small, conical, subiso- 

 dont; dorsal spines not elongate. Lower Permian. 



D. Caseasauria. Malacophagous; teeth small, isodont; dor- 

 sal spines short. Lower Permian. 



5. Therapsida. Skeleton less primitive; vertebrae amphicoelous, 

 rarely notochordal; dorsal intercentra absent or unknown; 

 phalangeal formula often reduced; propodials turned more or 

 less downward in locomotion. 



A. DiNOCEPHALiA. Skull massive; no secondary palate; quad- 

 rate large, temporal opening surrounded by postorbital 

 and squamosal; phalangeal formula primitive [?]. Upper 

 Permian. 



B. Dromasauria. Dentition subisodont or absent; no secon- 

 dary palate; phalangeal formula 2, 3, 3, 3, 3. Permian. 



C. Anomodontia. Edentulous or with long canine, or canine 

 and molars; a rudimentary secondary palate; an acromion; 

 phalangeal formula 2, 3, 3, 3, 3. Upper Permian, Triassic. 



D. Theriodontia. Carnivorous; dentition more or less hetero- 

 dont, at least one pair of caniniform teeth; phalanges and 

 teeth variable. Temporal opening extending to parietal in 

 later forms. Triassic. 



III. SYNAPTOSAURIA, A single temporal opening bounded below by 

 postorbito-squamosal arch; no supratemporal, interparietal or 

 tabulars. A single coracoid (? Placodontia). 



6. Sauropterygia. Vertebrae platycoelous ; no dorsal intercentra; 

 dorsal ribs single-headed, articulating with diapophysis; no 

 teeth on palate. Neck more or less elongated. 



A. NoTHOSAURiA. Amphibious; feet webbed; phalangeal for- 

 mula primitive; no interpterygoidal opening in palate. 

 Middle and Upper Triassic. 



B. Plesiosauria. Marine; limbs paddle-like, the propodials 

 long; hyperphalangic ; palate with openings. Triassic to 

 close of Cretaceous. 



7. Placodontia. Jaws and closed palate with heavy pavement 

 teeth; vertebrae deeply amphicoelous; dorsal ribs double-headed; 

 body with dermal bones; coracoids and feet unknown. Upper 

 Triassic. 



