dinosaurs lived so long ago it was very difficult to know
how they sounded, how they behaved, their skin color or
even how to tell whether a fossil was male or female.
were lots of different kinds of dinosaurs that lived at
different times. Some walked on two legs (they were bipedal),
some walked on four (they were quadrupedal). Some were
speedy and some were slow and some were armor-plated,
some had horns, crests, spikes, or frills. They even had
dinosaurs went extinct about 65 million years ago, at
the end of the Cretaceous period, which was a time of
high volcanic and tectonic activity. There are a lot of
theories why the extinction occurred. The most widely
accepted theory is that an asteroid impact caused major
climactic changes to which the dinosaurs couldn't adapt.