It seems to have lived on small food,
and been itself a rich diet to the larger carnivores. We find it
in all the seas of the Mesozoic world, varying in length from six
to forty feet, but it is one of the sluggish and unwieldy forms
that are destined to perish in the coming crisis.
The last, and perhaps the most interesting, of the doomed
monsters of the Mesozoic was the Pterosaur, or "flying reptile."
It is not surprising that in the fierce struggle which is
reflected in the arms and armour of the great reptiles, a branch
of the family escaped into the upper region. We have seen that
there were leaping reptiles with hollow bones, and although the
intermediate forms are missing, there is little doubt that the
Pterosaur developed from one or more of these leaping Deinosaurs.
As it is at first small, when it appears in the early Jurassic
--it is disputed in the late Triassic--it probably came from a
small and agile Deinosaur, hunted by the carnivores, which relied
on its leaping powers for escape. A flapperlike broadening of the
fore limbs would help to lengthen the leap, and we must suppose
that this membrane increased until the animal could sail through
the air, like the flying-fish, and eventually sustain its weight
in the air.
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