Although so different
superficially from the bird-footed biped Iguanodonts they are
evidently related to them, for the teeth are similar, and the horny
beak, the construction of the pelvis, the three-toed hind foot and
four-toed front foot all betray relationship. From what we know of
them it seems probable that they evolved from Iguanodont ancestors,
developing the bony armor as a protection against the attacks of
carnivorous dinosaurs, and modifying the proportions of limbs and feet
to enable them to support its weight. They were evidently herbivorous
and some of them of gigantic size. Smaller kinds with less massive
armor have been found in Europe but the largest and most extraordinary
members of this strange race are from North America.
STEGOSAURUS.
This extraordinary reptile equalled the Allosaurus in size, and bore
along the crest of the back a double row of enormous bony plates
projecting upward and somewhat outward alternately to one side and the
other. The largest of these plates situated just back of the pelvis
were over two feet high, two and a half long, thinning out from a base
four inches thick. The tail was armed with four or more stout spines
two feet long and five or six inches thick at the base. In the neck
region and probably elsewhere the skin had numerous small bony nodules
and some larger ones imbedded in its substance or protecting its
surface. The head was absurdly small for so huge an animal, and the
stiff thick tail projected backward but was not long enough to reach
the ground.
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