152 The History of the Earth: Supplemental Guide 8A | Dinosaurs
Show image 8A-3: Stegosaurus^6
Here is my personal favorite: the stegosaurus. Like the
triceratops, the stegosaurus was a herbivore, or plant eater, but it
had some pretty good ways of defending itself against the likes of
T. Rex and other meat eaters. Stegosaurus had hard, sharp plates
on its back, which would have made it diffi cult to bite. But just in
case anyone tried, the stegosaurus also had a spiky tail that could
really do some damage.
Show image 8A-4: Excavating dinosaur bones
How do we fi nd and learn about these incredible animals?
Some scientists believe that dinosaurs ruled the earth for more
than 100 million years, and their fossilized bones can be found in
many parts of the world, including the United States.^7 Dinosaur
fossils are hard to fi nd, and excavating—or digging up—their
bones is not as easy as you might think.
Once paleontologists fi nd an area that is likely to have dinosaur
bones, we move in with our tools and begin careful excavation.
Paleontologists must use sharp little knives and small brushes to
gradually scrape away the sedimentary rock surrounding the fossils. It
will take this paleontologist days and maybe even weeks to excavate
this one bone. It’s slow work, but to me there is nothing more exciting
in the world than carefully uncovering a bone that may have been
buried in rock for 100 million years.
Show image 8A-5: Large excavation
Here a paleontologist is excavating a large collection of bones
from the sandstone cliffs of Dinosaur National Monument, an area
located in the states of Colorado and Utah, where we have uncovered
hundreds and thousands of dinosaur bones.^8 Wow! Some of those
bones are bigger than the person working on them.
Can you see all the bones in this picture? That was one big
dinosaur! But what did it really look like? It’s hard to tell because,
over time, the bones have moved around and become broken. As
a paleontologist, I sometimes feel like I spend half my life putting6 How would you describe this
dinosaur?
7 Fossilized means that over a long
period of time the bones have
become like a fossil or rock.
8 [Locate Colorado and Utah on a U.S.
map for students.]