262 THE BIRDS 



Professor Huxley united the two classes in the Sauropsida, one of 

 his three primary divisions of the Vertebrata. 



Birds and mammals are related to one another only inasmuch 

 as they have both sprung from a common ancestry the reptiles 

 and resemble each other only in being warm-blooded, for although 

 birds and mammals are both derived from reptiles the two classes 

 of animals have developed on totally different lines. While the 

 birds gradually acquired those characteristics which enabled them 

 to conquer the air, the evolution of the mammals tended more and 

 more to fit them for a terrestrial life. 



But while it is certain that birds have come from a reptilian 

 stock, it is not possible to say from which particular forms they 

 are descended. The direct line of descent is lost in obscurity, 

 for there is very little rock record of prehistoric birds. The fossil 

 remains of the Archaeopteryx, the oldest known bird, are distinctly 

 reptilian in many ways ; two specimens of this curious bird are 

 in existence one in the Natural History Museum, and the other 

 in the National Collection of Berlin, both specimens having been 

 obtained from the lithographic slate of Solenhofen in Bavaria. 

 The Archaeopteryx was about the size of a large pigeon ; its head 

 was short, had no beak, and both jaws were provided with teeth ; 

 it had three distinct clawed fingers, and a long-lizard like tail bearing 

 a double row of feathers. In writing of the Archaeopteryx, Sir 

 E. Ray Lankester says: 1 " It cannot be said that this ancient 

 extinct bird goes far towards connecting birds with reptiles, but 

 in the possession of separate claw-bearing fingers, a long bony 

 tail and teeth, in the apparent want of a beak, it does come nearer 

 to lizard-like reptiles than does any other known bird." Although 

 the Archaeopteryx is the oldest bird of which we have any record, 

 it is certain that other more primitive forms must have existed 

 previously on the earth. At exactly what period in the world's 

 history the first reptilian vertebrate became a " bird " can only 

 be a matter of conjecture ; we can only be certain that the trans- 

 formation came about in very remote times, in all probability before 

 the advent of the Jurassic Period in which such strange birds as 

 the Archseopteryx flourished. 



Birds in their structure show a remarkable degree of uniformity, 

 which has been necessarily brought about by the requirements 



1 "Extinct Animals." Sir E. Ray Lankester. 



