The History of the Earth: Supplemental Guide 8A | Dinosaurs 153puzzles together. Often we only fi nd a few bones—the rest of the
skeleton was long since destroyed or perhaps even dragged away
by a predator many, many years ago. Other times, lots of different
dinosaur bones can be mixed in together. We paleontologists have
to use our detective skills to fi gure out which bones belonged to
which type of dinosaur.
Show image 8A-6: Excavating Camarasaurus
In fact, those bones belonged to a mighty Camarasaurus. I
knew as soon as I saw its head. This plant eater was sixty feet
long and weighed about twenty tons. 9 A real whopper! Show image 8A-7: Camarasaurus illustration
Here is one artist’s idea of what the Camarasaurus looked like.
It could use its long tail to fend off predators. Good thing you don’t
have to worry about these things anymore!
Show image 8A-8: Compsognathus^10
Not all dinosaurs were huge. In fact, some were really small.
Take the compsognathus. This little critter stood just two feet tall
and scurried around on two little bird-like legs. 11 Compsognathus
was a meat eater that fed on little lizards. We know this because
paleontologists found parts of fossilized lizard in the stomach
cavity of a compsognathus fossil.
Show image 8A-9: Tyrannosaurus Rex skeleton
What happened to the dinosaurs? You can’t go and see a
live T. Rex today at the zoo because dinosaurs are extinct. 12
Some scientists believe dinosaurs all died about 65 million years
ago. According to fossil records, the extinction of the dinosaurs
was quite sudden. Why? That’s something paleontologists have
been trying to answer ever since the fi rst dinosaur bones were
discovered and identifi ed nearly two hundred years ago.9 A ton is a unit of weight equal
to 2,000 pounds. That means
this dinosaur weighed the same
amount as 10 cars when it was
alive! [Show students a yardstick
and tell them that this dinosaur
was as long as twenty yardsticks.]
10 How would you describe this
dinosaur?
11 Two feet is less than the length of
one yardstick.
12 Remember, extinct means that
there are no more dinosaurs left.