THE FROG — A REPRESENTATIVE VERTEBRATE 



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Vertebral Column. The vertebral column, which forms a firm yet 

 movable support for the trunk, is a part of the axial skeleton. It is 

 unusually short in frogs, consisting in most species of only nine verte- 

 brae, jilus an elongate terminal piece known as the urostyle (Fig. 21.3). 

 The urostyle represents an uncertain number of caudal vertebrae fused 

 together and specialized for the attachment of powerful pelvic muscles. 

 The short, compact vertebral column is adapted for the frog's jumping 

 mode of progression. 



A representative vertebra consists of a ventral, spool-shaped centrum, 

 and a dorsal neural arch enclosing the neural canal, in which the spinal 

 cord lies. The neural arch bears a pair of prominent, broad, lateral 

 extensions called transverse processes, a small mid-dorsal neural spine, 

 and an articular process, or zygapophysis, on each dorsal corner. The 



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Figure 21.4. A, A ventral view of the frog's skull; B, a ventral view of the lower 

 jaw and hyoid apparatus. (After Gaupp.) 



