CLASSIFICATION, AND PHTLOGENT OF THE DINORNITHID^. 423 



Orbital process of quadrate bluntly pointed ; a large pneumatic foramen on mesial 



surface of otic process. 

 Mandibular symphysis broader than long, with a very obscure ventral ridge ; 



posterior angular process better developed than in any of the other genera. 



9. The Phtlogeny of the Eatitjs ^ 



The most definite opinion I have met vpith as to the phylogeny of the Eatitse is that 

 expressed in the elaborate genealogical tree which illustrates Fiirbringer's great work. 

 He ascribes a common origin to the Moas and Kiwis and to the Emus and Cassowaries, 

 but derives his four main groups of Ratitse — the Struthioniformes, JRheiformes, Casuari- 

 formes, and Apter^ygiformes — separately from a primitive stock. 



Mivart, in his memoir on the axial skeleton of the Ratitse (13), gives no definite 

 opinion as to the phylogeny of the group, but his diagram illustrating the mutual 

 relationships of the various genera seems to indicate his belief in their monophyletic 

 origin. He shows a main stem dividing into two branches ; one of these divides again 

 for Struthio and Bhea ; the other forks a second time, one branch dividing again for 

 Casuarius and Dromceits, the other for Linornis and Apteryx. 



The monophyletic origin of the Ratitse is also supported by Newton, who, in his 

 luminous article "Ornithology" (14), says "that these forms — Moa, Kiwi, Emu and 

 Cassowary, Rhea, and finally Ostrich — must have had a common ancestor nearer to them 

 than is the ancestor of any carinate form seems to need no proof." Prof. Newton's 

 classification indicates no closer affinity between any of the genera except the Emu and 

 Cassowary, which together constitute his order Megistanes ; each of the other genera 

 has an order to itself. 



A study of the skull certainly confirms the view that the nearest ally of the Dinor- 

 nithidse is Apteryx, and that the four families of Australasian Ratitae are more nearly 

 related to one another than is either of them to the A sio- African and South-American 

 forms. Struthio and Rhea differ so much from the Australasian members of the sub- 

 class as to lend strong support to Fiirbringer's view that they arose separately from a 

 primitive stock ; but whether the Cassowaries and Emus on the one hand and the Moas 

 and Kiwis on the other had a distinct or a common origin is a very complex question. 



The main difficulty lies in deciding what characters should be considered as of 

 phylogenetic importance and what merely adaptive, but it appears to me that in the 

 following particulars the Emu and Cassowary show an undoubted relationship to the 

 Moas : — 



The general characters of the maxilla, maxillo-palatine, and antrum in both 



' As my conclusions are based upon a study of the skull, I have omitted all reference to ^pyomisi 

 Dromornis, Megdlapteryx, and Pdlceocasuarinus. 



3o2 



