132 ANNALS NEW YORK ACADEMY OF SCIENCES 



Tyrannosaurus 

 Plate XIII, Fig. 1 



The reconstruction of this form was attempted after some comparative 

 study of types like Alligator, Ohelydra, Aves and JEuparkeria (Fig. 5). 

 The skull in Tyrannosaurus is secondarily monimostylic, as the quadrates 

 and the upper jaws were less movable than in the more primitive Allo- 



PlGURE 5 



Skull of a pseudosuchian, Euparkeria capensis. After Broom 



The borders of the large preorbital fenestra may serve for the attachment of the 

 anterior part of the pterygoideus anterior muscle. Around the bony margin of the 

 supratemporal fenestra arose the capiti-mandibularis. Both the supra- and the lateral 

 temporal fenestra gave room for the expansion of the capiti-mandibularis, while the 

 lateral fenestra of the mandible served a like function for the lower end of the same 

 muscle. 



gaurus. The monimostylic type is quite stable in its musculature and the 

 reason for this is evident, as the complicated musculature needed for the 

 movable quadrate and pterygoid is lost when the bones become fixed. 



Tyrannosaurus was a huge carnivorous type with massive skull and 

 jaws; thus the musculature must have been very heavy. 



