Answer:
Dinosaur communities were separated by both time and
geography. The "age of dinosaurs" (the Mesozoic Era)
included three consecutive geologic time periods (the
Triassic, Jurassic, and Cretaceous Periods).
Different
dinosaur species lived during each of these three
periods. For example, the Jurassic dinosaur
Stegosaurus already had been extinct for approximately
80 million years before the appearance of the
Cretaceous dinosaur Tyrannosaurus. In fact, the time
separating Stegosaurus and Tyrannosaurus is greater
than the time separating Tyrannosaurus and you.
At
the beginning of dinosaur history (the Triassic
Period), there was one supercontinent on Earth (Pangea).
Many dinosaur types were widespread across it.
However, as Pangea broke apart, dinosaurs became
scattered across the globe on separate continents, and
new types of dinosaurs evolved separately in each
geographic area.
