A third extinct subclass is that of the pterodactyls, or "flying dragons" (Pterosauria), which possessed the air throughout the Mesozoic Age, and filled the place of birds in the fauna of that period, although they had no relationship to the real birds that came later. Some were no larger than sparrows, but later ones spread their leathery wings twenty feet or more. The origin and real affinities of these winged reptiles are unknown and they left no descendants.

(Restoration, after Owen)