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EVOLUTIONARY MORPHOLOGY 



The early birds like Archaeopteryx (Jurassic) had a long 

 tail, jaws garnished with teeth, wings with three well-formed 

 ringers ending in claws, and a more or less flat sternum. At 

 the present day, birds have no teeth, and their tails are shortened 

 up, the fused vertebrae forming the pygostyle. 



Living birds are divided into two groups : Palaeognathae, 

 and Neognathae, according to the structure of the palate. In 



Fig. 178. — A few examples of different types of birds (not drawn to scale). 



a, Archaeopteryx ; b, bird of prey ; c, swift ; (both b and c are examples 

 of the Neognathas snowing highly perfected aerial adaptation) ; d, ostrich 

 (Palaeognathae, flightless) ; e, dodo (one of the Neognathae which lost the 

 power of flight) ; /, penguin (aquatic adaptation), (a after Pycraft.) 



the former (which include what used to be called the " flight- 

 less birds " or Ratites, plus the Tinamus), the prevomer is 

 large and touches the pterygoids ; whereas in the latter (the 

 so-called Carinates minus the Tinamus) the prevomer is small 

 and does not touch the pterygoids. In Tinamus and Neo- 

 gnathae the sternum bears a large keel or carina, on to which the 

 pectoral muscles (which are used in flight) are attached, and 

 the well-developed clavicles fuse together at their base to form 



