The Anatomy of Birds 23 



have originated from two distinct types of reptiles. Unfortunately, as previously 

 noted, these modifications can be described only in technical language and can 

 probably be best understood from a study of the accompanying figures. 



In the dromaeognathous type of skull (Figs. 14, 15), so called because it is 

 typically found in Ostriches, the vomer is broad and unites in front with the 

 maxillopalatines, while behind it receives the posterior extremities of the pala- 

 tines and the anterior ends of the pterygoids, which are thus shut out from 

 joining the sphenoid; the sphenoid bears on its sides long basipterygoid pro- 

 cesses which give it something of a cruciform shape. In birds with this type of 

 skull the quadrate, the bone to which the lower jaw is joined, is rather short and 

 clumsy and its articular head is single or but faintly divided into two portions; 

 the quadrate is also locked into place by the surrounding bones. In all these 

 particulars the dromaeognathine skull more nearly resembles that of a reptile 

 than does that of the majority of birds, a point that may be best appreciated by 

 comparing the figures. 



In the euornithic type of skull (Fig. 16) the palatines articulate with the 

 pterygoids and both touch the sphenoid at their point of junction, and the back 

 of the vomer embraces the sphenoid between and above the ends of the palatines. 

 The quadrate has two heads and is loosely joined to the cranium. This arrange- 

 ment prevails in the majority of birds, and is termed the euornithic type of skull 

 because it is characteristic of the Euornithes; it is also called neognathic because 

 it is believed to be more recent or newer than the Ostrich style and further 

 removed from the reptilian skull. 



Basipterygoid processes may be present, but usually in the form of low facets 

 which articulate with projections on the pterygoids and often serve as braces to 

 the beak when this is slightly movable, as in Ducks and Parrots. 



The neognathous style of skull is subject ~to several important modifications 

 which characterize great natural groups of birds. These are the schizognathous, 

 desmognathous, and aegithognathous types, 1 which may be briefly characterized 

 as follows : When the vomer is pointed in front and entirely free from the maxillo- 

 palatines, and these are free from each other, the skull is termed schizognathous; 

 when the maxillopalatines are expanded and fused with each other, the vomer 

 being small or absent, the skull is desmognathous; when the vomer is expanded 

 in front and free from the maxillopalatines, and these are slender at their point 

 of origin and disjoined, the skull is said to be segithognathous. 



The second of these types, the desmognathous, is to some extent a modification 

 of the first, brought about by the development of bone in the palatal region which 

 binds the various parts together and hides its real structure. Thus desmognath- 

 ism occurs in varying degrees in birds obviously closely related, while the trans- 

 formation of one type of skull into another is admirably illustrated by the Cor- 

 morant. This bird has at first a schizognathous skull, but by the time it takes 



1 Parker applied the term saurognathous to the skulls of Woodpeckers, but in the opinion of 

 the writer and others, the modifications found in the skulls of these birds are largely, if not entirely, 

 mechanical and depend on the use of the skull as a pick. To a lesser extent and for similar 

 reasons some of the features are present in the skull of the Nuthatch. 



