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His teeth, as I have explained above, do not separate 
him from the bird. In fact, it is far more a bird’s 
head than a reptile’s. Proceeding now to the long 
bones we find that many of them have a very 
remarkable feature ; they have undoubted air cavities. 
These two points—the birdlike character of the skull, 
and the aeration of the bones—are, I think, the most 
important of all. When they are combined with power 
of flight we can infer from them other characters of 
Fic. 18.—Pterodactyl, Rhamphorhyncus phyllurus restored (after Marsh). 
which no direct evidence is obtainable, and principally 
this—the pterodactyl must have been a warm-blooded 
animal. Flight requires great vigour such as is not 
found in any cold-blooded creature. Flying-fish can 
hardly be said to fly, nor can the so-called Flying 
Dragon. Its wings are merely parachutes. Moreover 
no animal that we know of combines a highly-developed 
brain with cold blood. Among existing animals, birds, 
who on the average have a decidedly higher tem- 
perature than mammals, have, very many of them, 
pneumatic bones. It is true that the same tendency 
to pneumaticity is found in the bones of the Dinosaurs, 
