The best way to tell apart the two main kinds of
dinosaurs is hip structure. One major group
of dinosaurs (ornithischians) is characterized by
a bird-like hip (ornitho = bird, ischium is a hip
bone), and the other major group of dinosaurs
(saurischians) has a lizard-like hip (saur = lizard).
Somewhat confusingly, one group of saurischian
dinosaurs developed a bird-like hip independently
of the bird-like hip in ornithischians. This
unusual group of saurischians with bird-like hips
includes, perhaps no surprisingly, birds, and
their closest relatives, including small-bodied,
meat-eating dinosaurs such as Velociraptor. This
is one of the major reasons scientists think that
birds ARE a kind of dinosaur.
There are many different kinds of dinosaurs, and
they are different from each-other in different
Since the only living dinosaurs are birds, it
is easiest to imagine the differences that
distinguish different kinds of birds. Extinct
species of dinosaur probably were different in
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