They were probably
much like the modern lizards in size, appearance and habitat:[2]
From this ancestral type the Dinosaurs evolved into a great variety of
different kinds, many of them of gigantic size, some herbivorous, some
carnivorous; some bipedal, others quadrupedal; many of them protected
by various kinds of bony armor-plates, or provided with horns or
spines; some with sharp claws, others with blunted claws or hoofs.
[Illustration: Fig. 6.--Outline Restorations of Dinosaurs. Scale
about nineteen feet to the inch.]
These various kinds of Dinosaurs are customarily grouped as follows:
I. _Carnivorous Dinosaurs_ or _Theropoda_. With sharp pointed teeth,
sharp claws; bipedal, with bird-like hind feet, generally
three-toed;[3] the fore-limbs adapted for grasping or tearing, but not
for support of the body. The head is large, neck of moderate length,
body unarmored. The principal Dinosaurs of this group in America are
_Allosaurus_, _Ornitholestes_--Upper Jurassic period.
_Tyrannosaurus, Deinodon, Albertosaurus, Ornithomimus_--Upper Cretacic
period.
[Illustration: Fig. 7.--Skulls of Dinosaurs, illustrating the
principal types--_Anchisaurus_ after Marsh, the others from
American Museum specimens.]
II. _Amphibious Dinosaurs_ or _Sauropoda_. With blunt-pointed teeth
and blunt claws, quadrupedal, with elephant-like limbs and feet, long
neck and small head. Unarmored. Principal dinosaurs of this group in
America are _Brontosaurus_, _Diplodocus_, _Camarasaurus_
(_Morosaurus_) and _Brachiosaurus_, all of the Upper Jurassic and
Comanchic periods.
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