A comprehensive view of nature, living and non-living,
past and present, discovers scores of illuminating connections,
and even sees at times the inevitable sequence of events. Thus if
the rise of the Angiospermous vegetation on the ruins of the
Mesozoic world is understood in the light of geological and
climatic changes, and the consequent deploying of the insects,
especially the suctorial insects, is a natural result, the
simultaneous triumph of the birds is not unintelligible. The
grains and fruits of the Angiosperms and the vast swarms of
insects provided immense stores of food; the annihilation of the
Pterosaurs left a whole stratum of the earth free for their
occupation.
We saw that a primitive bird, with very striking reptilian
features, was found in the Jurassic rocks, suggesting very
clearly the evolution of the bird from the reptile in the cold of
the Permian or Triassic period. In the Cretaceous we found the
birds distributed in a number of genera, but of two leading
types. The Ichthyornis type was a tern-like flying bird, with
socketed teeth and biconcave vertebrae like the reptile, but
otherwise fully evolved into a bird.
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