PYROTHERII'M 



157 



1 Upper tush 



PvROTHERHM PAI.AEOMASTODON 



Inc. 1 enlarged Inc. 1 enlarged in 

 Inc. 2 tush 



Toxodont, 

 Nesodon 



DlPROTODON 



Inc. I reduced 'Inc. 1 tush 

 Moeritherium. Inc. 2 caniniforml 

 Inc. 2 tush tush |Inc. 2 reduced 



2 L'pper molars 



3 Lower tush 



4 Lower molars 



Bilophodont 



Bilophodont in Rhinoceros-like Bilophodont 

 Mastodon and 

 Dinotherium 



Inc. 2 (?) 



Inc. 2 



Inc. 3 



ilnc. 1 



Bilophodont Bilophodont in Bicrescentric 



Mastodon and 

 Dinotherium 



Bilophodont 



5 Nasal opening 



Pterygoids 



Over molar 1 



Over molar 1 



Over incisors 



Over diastema 



6 Basicranial axis Plane of base of Plane of base of Plane of base of 1 Plane of base of 



cranium bent up, cranium bent up, cranium parallell cranium parallel 

 makes 140 with makes 155° with with plane of with plane of 

 plane of palate plane of palate palate palate 



Pterygoids plus Petrygoids plus Pterygoids normal Pterygoids normal 

 alisphenoids alisphenoids 

 make great verti- make great verti- 

 cal plates cal plates 



8 Jugal 



Takes small part Takes small part Takes no part on Extends to glenoid 

 on glenoid fossa on glenoid fossa glenoid fossa fossa 



9 Posttympanic process of Surrounds meatus. Surrounds meatus Surrounds meatus Not surround me- 

 squamosum and crowds out and crowds out and crowds out' atus nor crowd 



tympanic tympanic ' ' tympanic out tympanic 



10 Tympanic bulla 



Small, inflated. Small, inflated. Large, inflated 

 1 hollow hollow hollow 



1 1 Palatine bones Narrow in front, Narrow in front. Wide in front, nar- 



e.xpanding behind expanding behind rowing somewhat 



behind 



12 Premaxilla 



Crowded out from Crowded out from Makes front of. Fused to maxilla 

 forming any por- forming any por- palate 

 tion of palate tion of palate 



13 Antorbital foramen 



2 foramena 



2 foramena 



1 foramen 



1 1 foramen 



14 Intercellular laminae Present 



Present 



None 



I None 



15 Atlas 



Long, has hypo- Long, has hypo- Long, no hypo- Short, no hypo- 

 physis physis physis physis 



16 Axis 



hemispherical Rounded odontoid Peg like odontoid Odontoid slightly 

 I odontoid flattened on top 



