10 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



SYSTEMATIC REVISION. 



Order COTYLOSAURIA Cope. 



Cotylosauria Cope, Am. Nat., vol. Xiv, 1880, p. 304. 

 Cotylotnuria Cope, Am. Nat., vol. XXllI, 1889, p. 866. 

 Cotylosauria Cope, Proc. Am. Phil. Soc., vol. XXXIV, 1896, p. 436. 



Original description: In 1880, in describing the skull of Empedocles Cope men- 

 tions the supposed peculiar method of articulation of the skull with the cervical ver- 

 tebrae; this was due to the falling out of the basioccipital bone, giving the appearance 

 of a double occipital condyle. Upon this error the order was founded. Cope says: 



"The character of the articulation is so distinct from anything ytt known 

 among the vertebrated animals that I feel justified in proposing a new division of 

 the Theromorpha, to include the Diadectida, to be called the Cotylosauria." 



In the "American Naturalist" of 1889 Cope gives an analysis of the order on 

 other grounds than the occipital articulation: "Ribs single-headed; temporal fossa 

 overroofed; dentition abundant; intercentra." 



In the "Proceedings of the American Philosophical Society" for 1896 he re- 

 described the Cotylosauria: 



"Quadrate bone united by suture with the adjacent elements. Temporal 

 fossa overroofed by the following elements: Postfrontal, postorbital, jugal, supra- 

 mastoid (squamosal), supratemporal (prosquamosal), quadratojugal. Tabular bone 

 present. Vertebr?e amphicoelous; ribs one-headed. Epistemum present. Pelvis 

 without obturator foramen." 



Revised description: Primitive reptiles with the temporal region complete; over- 

 roofed by two elements, squamosal and prosquamosal, or three, squamosal, prosqua- 

 mosal, and quadratojugal. Quadrate covered or exposed. Ribs single-headed. 

 Neural arches broad and low, the sides swollen and convex, spines short and stout. 



The order is assumed to include all the early reptilia with complete skulls, 

 indicating their primitive relationship to the Stegocephalia. It is meant to include 

 the suborders Diadectosauria, Pareiasauria, Procolophonia, and Pantylosauria. 



Suborder DIADECTOSAURIA nov. 



1. Skull completely overroofed with the exception of the posterior angle, where 



the quadrate and the external auditory opening are exposed. 



2. Upper end of the quadrate bent backward and downward in a hook. The 



external face of the quadrate concave, forming a funnel with the apex at 

 the notch formed by the hook described. 



3. Temporal region covered by two bones, squamosal and prosquamosal. 



4. External process of the pterygoid absent or poorly developed; edentulous. 



5. Parasphenoid rostrum not appearing on the lower surface of the skull be- 



tween the pterygoids. 



6. Ectopterygoids absent or rudimentary. 



7. Tabulare absent or doubtfully present. 



8. Cheek teeth expanded transverse to axis of jaw. A single row in each jaw. 



9. Hyposphene-hypantrum articulation present. 



10. Coracoid and procoracoid united with the scapula. Cleithrum present. 



11. Ischium and pubis broad and plate-like. 



12. Abdominal ribs absent (?), not observed in any specimen.* 



*The chancteri ol the reriied dcKription of the ordcri, nibordrn, f imiliei, and genera are arranged with senal nurabert, the 

 aame for each group, to that thej can be compared directly 



