CHAPTER II 



PHYLOGENETIC 



Birds and their position in the animal kingdom. Relationship to the 

 reptiles, and the evidence thereof. Archsopteryx — the first bird. Hesperornis 

 and early specialisation. Ichthyornis. The Pro-aves. 



AT the outset it is well that a clear conception should be 

 gained as to the relationship of birds with regard to 

 other classes of the Vertebrate kingdom : and this 

 relationship can be established more clearly perhaps with 

 regard to the birds than in any other group. 



Agile apd restless to a degree unequalled perhaps in the 

 animal kingdom, it may seem surprising to many to learn that 

 nevertheless they owe their descent to the sluggish and cold- 

 blooded reptiles : yet such is the case. Like the reptiles they are 

 oviparous, though, unlike the reptiles, none are ovoviviparous. 

 Furthermore, they differ from their humbler allies in that their 

 eggs require a higher temperature to incubate. This is 

 generally obtained by the brooding of the parent, though in 

 certain exceptional cases this is secured by depositing the eggs 

 in fermenting vegetable matter, or by the aid of sand heated 

 by warm springs (p. 218). 



Structurally their reptilian character is abundantly plain. 

 In the skeleton this is manifested in several ways. 



The skull alone would furnish sufficient evidence to prove 

 this relationship, but happily many other parts of the skeleton 

 can be made to bear no less striking evidence. These char- 

 acters may profitably be reviewed, though briefly, here. 



First of all as to the skull. As in the reptiles this articulates 

 with the vertebral column, or backbone, by means of a single 

 condyle — a rounded boss of bone projecting from the floor of 

 the skull immediately below the aperture for the exit of the 

 spinal cord — while the bones of the palate and of the cranium 



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