KINESIS OF AVIAN SKULL — ZUSI 



17 



In Balaeniceps (fig. 9), the quadrate has two main condylar sur- 

 faces, the inner of which (medial condyle) forms a double crest lying 

 parallel to the plane of movement of the quadrate. The lateral 

 condyle is somewhat curved, lying approximately perpendicular to 

 the crest and to the plane of quadrate motion (its posteromedial 



medial 

 condyle 



latera 

 condyle 



lateral articular 

 surface 



medial 



articular 



trough 



flan 



2 e 



lateral 

 condyle 



Bdl&eniceps rex 



medial 



articular 



surface 



medial 

 condyle 



depression Utera 

 condyle 



articular 

 surface 



late ra 

 posterior articular 

 condyJe surface 



Hesperiphona vespertine Gallus domesticus 



Figure 9. — Structure of jaw articulation in Balaeniceps rex, Hesperiphona vespertina, and 

 Gallus domesticus. (Ventral view of right quadrate and dorsal view of left articular 

 shown for each species.) 



portion is expanded into a prominent condyle that is often referred to 

 as the posterior condyle of the quadrate). These condyles fit into 

 corresponding depressions or surfaces of the articular bone, and flanges 

 on the upper edges of the medial articular trough grip the crests of 

 the medial condyle of the quadrate, holding the articulated lower 



