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The Theropods
The Theropods varied considerably in size and agility. The
Compsognathus was a small, active, rabbit-like creature, standing
about two feet high on its hind limbs, while the Megalosaurs
stretched to a length of thirty feet, and had huge jaws armed
with rows of formidable teeth. The Ceratosaur, a
seventeen-foot-long reptile, had hollow bones, and we find this
combination of lightness and strength in several members of the
group. In many respects the group points more or less
significantly toward the birds. The brain is relatively large,
the neck long, and the fore limbs might be used for grasping, but
had apparently ceased to serve as legs. Many of the Theropods
were evidently leaping reptiles, like colossal kangaroos, twenty
or more feet in length when they were erect. It is the general
belief that the bird began its career as a leaping reptile, and
the feathers, or expanded scales, on the front limbs helped at
first to increase the leap. Some recent authorities hold,
however, that the ancestor of the bird was an arboreal reptile.
To the order of the Sauropods belong most of the monsters whose
discovery has attracted general attention in recent years.
Feeding on vegetal matter in the luscious swamps, and having
their vast bulk lightened by their aquatic life, they soon
attained the most formidable proportions. The admirer of the
enormous skeleton of Diplodocus (which ran to eighty feet) in the
British Museum must wonder how even such massive limbs could
sustain the mountain of flesh that must have covered those bones.
It probably did not walk so firmly as the skeleton suggests, but
sprawled in the swamps or swam like a hippopotamus. But the
Diplodocus is neither the largest nor heaviest of its family. The
Brontosaur, though only sixty feet long, probably weighed twenty
tons. We have its footprints in the rocks to-day, each impression
measuring about a square yard.
Generally, it is the huge
thigh-bones of these monsters that have survived, and give us an
idea of their size. The largest living elephant has a femur
scarcely four feet long, but the femur of the Atlantosaur
measures more than seventy inches, and the femur of the
Brachiosaur more than eighty. Many of these Deinosaurs must have
measured more than a hundred feet from the tip of the snout to
the end of the tail, and stood about thirty feet high from the
ground. The European Sauropods did not, apparently, reach the
size of their American cousins-- so early did the inferiority of
Europe begin--but our Ceteosaur seems to have been about fifty
feet long and ten feet in height. Its thigh-bone was sixty-four
inches long and twenty-seven inches in circumference at the
shaft. And in this order of reptiles, it must be remembered, the
bones are solid.
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