AFFINITIES 417 



vergent analogies. The upright walk, which has been assumed 

 and improved upon independently by members of both Theropoda 

 and Orthopoda, has produced the same, or nearly the same 

 modifications in them as in the birds. 



It is easy to show that these features are mere coincidences. 

 The oldest bird known is Arcliaeopteryx from the Upper Oolite of 

 Bavaria. Consequently all those Dinosaurs, which are of the 

 same and of later date, have to be excluded from the supposed 

 ancestry, and they happen to be those in which (as in Ceratosaurus, 

 Compsognatlius, Ornithomimus, Iguanodon) the resemblances are 

 greatest. There remains only Anchisaurus of the Upper Trias r 

 more or less contemporary with the Brontozoum, which left its 

 three-toed footprints (Arcliaeopteryx has four well-developed toes) 

 with Zanclodon. Moreover, the most bird-like foot is either that 

 of the Theropoda, which, like Anchisaurus and Zanclodon, differ 

 from birds by the formation of the pelvis, or of some of the 

 latest Ornithopoda. What, then, is the good of selecting a 

 number of bird-like features from members of Dinosaurs \vhich 

 we are bound to class in different groups, and which existed, 

 some in the lower, others in the middle, or even in the latest 

 Mesozoic periods ? 



Lastly, the advocates of the Dinosaurian ancestry of birds 

 cannot have fully appreciated the enormous differences between 

 the wing of Arcliaeopteryx and the fore-limb of any Dinosaur 

 with the most avian resemblances in the hind-limbs. The fore- 

 limbs o'f these reptiles are modified in a direction diametrically 

 opposed to that from which a bird-like wing could be developed. 

 The skull presents another difficulty, and here again Compsognatlius, 

 a contemporary of Archaeopteryx, comes perhaps nearest to that of 

 a generalised bird's skull. The ancestors of the birds must have 

 combined the following characters : Of not later than Mid-. 

 Oolitic age, with bifurcated pubic bones, four functional toes, elon- 

 gated metatarsals, complete clavicles, premaxillary teeth, and free, 

 not firmly fixed quadrate bones. But such creatures are not 

 Dinosaurs. 



We divide the enormous number of Dinosaurs according to 

 the formation of the pelvis, that of the hind -limbs, and the 

 dentition, into four orders. 



VOL. vin 2 E 



