SYSTEMATIC REVISION 63 



COMPARATIVE TABLES. 



Table I. — Showing the Characters of the Order Cotylosauria. 



CHARACTERS COMMON TO THE PRIMITIVE REPTILES. 



1. Vertebrae notochordal or deeply amphicoelous. 



2. Intercentra present. 



3. Entepicondylar foramen present (except in most primitive forms Eosauravus (?) and Sauravus). 



4. Ischium and pubis flat and plate-like. 



5. Five elements in the distal row of the tarsus (when ossified). 



6. Abdominal ribs present ( ? ). 



CHARACTERS DISTINCTIVE OF THE COTYLOSAURIA. 



1. No openings in temporal portion of the skull. 



2. Neural arches of the vertebrse broad and low; sides of arches swollen; neural spine low and stout. 



3. Teeth tending to become elongate transversely to the axis of the jaw and to become tuberculate. 



4. Herbivorous. 



5. Body relatively short and low. The limb bones decidedly short and strong with powerful muscular 



attachment. 



6. Neck so short as to be practically absent. 



7. Ribs single-headed. 



, _,. , Table II. — Contrasting the Suborders of the Cotylosauria. 



I. Diadectosauna. * ' ^ 



1. Quadrate and external auditory opening exposed by the cutting away of the posterior edge of 



the roof of the skull. 



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



quadrate concave and forming a funnel with its apex at notch formed by hook mentioned. 



3. Temporal region covered by two bones, the 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 between the pterygoids. 



6. Ectopterygoids rudimentary or absent. 



7. Tabulate absent or doubtfully present. 



8. Cheek teeth expanded transversely to the axis of the jaw. A single row of teeth 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. 



II. Paretasauria. 



1. Skull completely overroofed. Quadrate concealed. 



2. Quadrate without the hook marking the opening of external meatus. 



3. Temporal region covered by two bones, the squamosal and prosquamosal (quadratojugal). 



4. External process of the pterygoid present (indeterminable in Pareiasaurus), with numerous 



small teeth. 



5. Parasphenoid rostrum appears on the lower surface of the skull between the pterygoids. 



6. Ectopterygoid present. 



7. Tabulate present, often small. 



8. Cheek teeth obtusely conical, one or more than one row in the jaws. Tuberculate or simple. 



9. Hyposphene-hypantrum articulation absent. 



10. Coracoid and procoracoid united with scapula (free in Pareiasaurus). 



11. Ischium and pubis broad and plate-like; horizontal or the two sides meeting at an angle. 



12. Abdominal ribs present or absent (?). 



III. Pantylosauria. 



1. Temporal region completely overroofed. 



2. Quadrate covered or exposed; without a posterior hook forming an external meatus. 



3. Temporal region covered by three bones, the squamosal, prosquamosal, and quadratojugal. 



4. External process of pterygoid present and covered with small teeth. 



5. Parasphenoid rostrum appearing on the lower surface of the skull. 



6. Ectopterygoid present. 



7. Tabulate present. 



8. Cheek teeth simple, conical; one or more than one row in each jaw. 

 9,10,11,12. Not determinable. 



