5.7D: What Happened Before
Earth and Space
Lone Star Dinosaur
Lexile 800L
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Long ago, a female dinosaur was looking for food
by a streambed in what would someday be known
as the state of Texas. She had been traveling with
a group of other dinosaurs that decided it was time
to stop for food. The young dinosaurs searched for
plants close to the streambed while the adults
formed a circle around them. That way they would
be protected from any predators that might be
nearby. They soon found what they wanted and
left. When they left, they left behind tracks in the
soft mud of the streambed.
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These footprints were not disturbed for a long time. About 110 million years later, scientists
found the tracks near Glen Rose, Texas. They found bones nearby, too. Scientists studied
these tracks and bones, and they named the dinosaur Pleurocoelus (PLOOR-oh-SEEL-us).
Later, they also found the tracks of another dinosaur. That one seemed to have been
chasing the Pleurocoelus!
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Of course, it is hard to know for sure what happened. This is because scientists could not
observe a living dinosaur to see what it ate or how it behaved. There are special scientists
called paleontologists. They are able to use clues left behind by dinosaurs to infer what
the dinosaurs’ lives were like.
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For example, the tracks left in the mud tell scientists much about the animals who made
them. The size of the footprint can tell the scientists approximately how big the dinosaur
was. The distance between tracks can tell them whether the animal was running or walking.
The number of footprints in an area can tell them whether the animal lived alone or in a
group.
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Paleontologists used other clues to figure out what dinosaurs ate. The Pleurocoelus, for
example, had weak teeth. This tells scientists that the animal was an herbivore, or planteater. It did not need strong and sharp teeth like those of a meat-eating carnivore.
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From these bones and tracks, paleontologists have been able to create a pretty good
picture of the Pleurocoelus. For one thing, they can tell that it was a quadruped. This
means that it had four legs. Another thing they can tell is that a female might have
weighed close to 20 tons. That is about the same as 10 small cars! They also know that the
female’s front legs were longer than her back legs. And, they know that she had a small,
narrow head on a long neck - just like a giraffe’s. But, unlike a giraffe, she had a bulky body
and a long tail.
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5.7D: What Happened Before
Earth and Space
Continued
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Because of the many tracks and bones of Pleurocoelus found in Texas, the state of Texas
passed a bill that made Pleurocoelus the official Lone Star State Dinosaur. Today, the place
on the streambed where the tracks were left is part of Dinosaur Valley State Park, where
visitors can see the footprints for themselves. In fact, this park is one of the best places to
see dinosaur tracks. You should call before you go to visit because the tracks are in the
riverbed. This means that you will not be able to see them when the river is too high.
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5.7D: What Happened Before
Earth and Space
1
2
3
Which of the following is NOT TRUE of Pleurocoelus?
A
It had weak teeth.
B
It had a long neck.
C
It lived in a group.
D
It did not have any predators.
How do you think scientists know the carnivore was chasing Pleurocoelus?
(paragraph 2)
A
The carnivore tracks came behind the Pleurocoelus tracks.
B
The carnivore’s teeth were found near the Pleurocoelus.
C
The Pleurocoelus was protecting its young.
D
The carnivore was small.
Why did the author probably write this passage?
A
To tell a story about a mother dinosaur
B
To describe how clues from fossils can tell us about the past
C
To persuade the reader that the Pleurocoelus should be the state
dinosaur
D
To give information about Dinosaur Valley State Park
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5.7D: What Happened Before
Earth and Space
4
5
Which of the following is a quadruped? (paragraph 6)
A
A human
B
A parrot
C
A horse
D
A tree
What is something a paleontologist probably would not do?
A
Look at fossilized bones
B
Try to use dinosaur tracks to find out what the dinosaur weighed
C
Hide fossils so no one else could find them
D
Measure the distance between dinosaur tracks
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