5 3 3 paleontology digging for dinosaurs and more

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Life Science

Paleontology:
Digging for Dinosaurs and More

Genre

Expository
nonfiction

Comprehension
Skills and Strategy

• Fact and Opinion
• Cause and Effect
• Predict

Text Features

• Captions
• Headings
• Glossary

Scott Foresman Reading Street 5.3.3

ISBN 0-328-13538-0

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by Laura Johnson


Vocabulary
erected
foundations
mold

Reader Response

Paleontology:

1. Using a graphic organizer like the one below, record
three facts about dinosaurs in the left-hand column.
Then write your opinion of this information in the
Digging
for Dinosaurs and More
right-hand
column.
Fact

by Laura Johnson
Opinion

occasion
proportion
tidied

2. What do you think paleontologists will do in the
future? On what facts are you basing your prediction?

workshop

3. What are some things you can think of, other than
dinosaur replica bones, that might be made in a
mold?

Word count: 1,597

Note: The total word count includes words in the running text and headings only.
Numerals and words in chapter titles, captions, labels, diagrams, charts, graphs,
sidebars, and extra features are not included.

4. What question would you most like to ask a
paleontologist? Why?

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What Is Paleontology?
Paleontology is the study of living things that died
before people kept records. If none of these living
things are around today, how do we know they once
lived? Through the study of fossils!
Fossils are preserved, or saved, remains that offer
proof of plant or animal life from long ago. There

are two types of fossils. One type is body fossils.
These are remains of body parts, such as bones, that
have been preserved over the years. The second kind
is trace fossils. These are clues left behind by animals,
such as footprints, tracks, and bite marks.

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Bones are examples of
body fossils. Footprints and tracks
are examples of trace fossils.

ISBN: 0-328-13538-0
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3


From Bones to Fossils
Fossils can form when plants and animals die and
fall to the ground. Plants and animals die all the
time, but fossils are rare. This is because conditions
must be perfect for a fossil to form.

3. Layers of mud, sand, clay, and rock build up on
top of the skeleton. Their weight presses down.
Over many years, the pressing causes the layers to
stick together and form rock.

Let’s look at how a fish can become a fossil.
1. First, the fish dies in a place where there is little
air, such as the bottom of the ocean. Or it dies at
the surface and sinks to the bottom.

4. The fish is now preserved in solid rock. If the fossil
is discovered and studied, it will provide clues
about the fish that once lived.

2. Minerals in the water work their way into the
fish’s bones and body parts. After a long time, all
the bone in the skeleton is replaced by minerals
that harden and turn into stone.

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5


Paleontologists at Work
Paleontologists are scientists. They study
prehistoric life by examining fossils. They know
how to “read” fossils. By studying a fossil, a
paleontologist might be able to tell the size of an
animal, where it lived, what it ate, and more.
The first thing paleontologists do when they find
a fossil is map the area around it. This area is called
the excavation, or digging, site. They make a grid, a
type of graph, of the site to keep track of the fossils.

Recording the exact location
of each fossil on a site map is
extremely important.

6

Protective gear prevents
injury from flying slivers
of rock.

Excavation tools range in size from tiny
drills to heavy jackhammers. Very large
jobs may require cranes and explosives.

Fossils can be fragile. Paleontologists often brush
them with glue to give them strength and prevent
chipping. When a fossil is ready to be sent to a
workshop, it’s wrapped in paper or foam and packed
in bags. Larger fossils are wrapped in casts similar to
the ones that doctors put on broken arms or legs.
Often the fossils sent back to the workshop have
bits of rock still stuck to them. Paleontologists at the
workshop use tools to remove the bits of rock.
Then the fossils are tidied up. Paleontologists tidy
them by removing even tinier bits of rock. They use
microscopes to help them avoid chipping the fossils.

7


Preparing Fossils for Display
Putting together an animal’s fossils to create a
museum exhibit is very difficult! Most fossils are too
delicate to be put on display. Instead, replica, or
look-alike, bones are used.
To make replica bones, workers create a mold of
each fossil bone. The mold is created by painting a
bone with layers of a rubbery material. After the
material dries, workers peel it away from the bone.
Next, the mold is filled with either plastic or
plaster. When this material hardens, the mold is
peeled away. There is now a replica of the bone.
The replica is painted to look like the original fossil.
Sometimes, if a fossil skeleton is not complete,

workers need to create replacement parts. The
replacement parts must be in the right proportion to
the rest of the bones.
When the painting is finished, the replica bones
are ready to be connected in the shape of the
animal. Workers build a frame to support the rebuilt
skeleton. The frame is arranged to show how the
animal stood.
Once the frame is erected, paleontologists lay
out the replica bones and arrange them correctly.
Starting at the foundation, the bones are attached
to the frame. Then the model is ready for display!

8

A worker creates a mold of a
dinosaur skull.

9


The Finished Product: Sue
One of the most famous fossils is a Tyrannosaurus
rex named “Sue.” Sue was named after fossil hunter
Sue Hendrickson. She discovered the fossils in 1990.
Sue is the largest, most complete, and best preserved
Tyrannosaurus rex yet discovered. Of the more than
250 bones in a Tyrannosaurus skeleton, only one
foot, one arm, and a few ribs and back bones are
missing from Sue.

It took six paleontologists seventeen days to
excavate the fossil of Sue. Then, it took a group of
ten workers two years to clean the bones and piece
them together!
You might be asking, do paleontologists ever
make mistakes when they make models of extinct
dinosaurs? Sometimes they do. The first replica made
of a dinosaur was a model of an Iguanodon. When
scientists first pieced its bones together, they decided
that one of the bones was a horn. Years later, other
scientists realized that that bone was not a horn. It
was a spike on the dinosaur’s thumb! On another
occasion, the head of one kind of dinosaur was
attached to the body of a different dinosaur.

10

Sue can be seen at the Field
Museum in Chicago, Illinois.

11


Always Learning
Paleontologists study chemistry, biology, zoology
(the study of animals), and geology (the study of
Earth). They also study math and computer science.
Paleontologists often learn several languages. This is
because their work takes them all over the world!
There are only about one hundred dinosaur

paleontologists in the world today, but they discover
an average of seven new kinds of dinosaurs a year!
As new fossils are collected and studied, what they
know about dinosaurs changes.
For example, paleontologists once thought that
Tyrannosaurus rex was the largest meat-eating
dinosaur. Then, in 1995, fossils were found in
Argentina of a meat-eating dinosaur that was even
larger than Tyrannosaurus rex. Scientists named
this dinosaur Giganotosaurus.
Giganotosaurus and
Tyrannosaurus rex lived
at different times and in
different places, so they
would never have met.

Tyrannosaurus rex was
a huge meat-eating
dinosaur. For years,
scientists have been
puzzled about its tiny
arms. Its arms were
so short that they
couldn’t even reach
its mouth!

Giganotosaurus was bigger
than Tyrannosaurus rex.
However, scientists think it had
a smaller brain, less powerful

jaws, and narrower teeth than
Tyrannosaurus rex.

12

13


More Recent Discoveries
Paleontologists have known for a long time that
most plant-eating dinosaurs were bigger than their
meat-eating relatives. For a while they thought that
the largest plant-eating dinosaur was Brachiosaurus.
This huge dinosaur was about 90 feet long and
weighed roughly 75 tons. In 1979 fossil hunters in
New Mexico discovered fossils of an even larger planteater. They named it Seismosaurus, meaning “earthshaker.” This dinosaur may have been 120 feet long
and may have weighed nearly 90 tons!
Using computer technology, some paleontologists
have decided that Seismosaurus could move its tail
faster than the speed of sound. There is one thing
we know for sure about the tail of Seismosaurus: It
was huge!

In 1996, scientists
in China found a fossil
skeleton of a small
dinosaur that they named
Sinosauropteryx. The fossil
had feather-like markings.
Up until then, scientists

thought all dinosaurs were
cold blooded. The discovery
of what might be feathers
on the Sinosauropteryx
fossil meant that some
Sinosauropteryx
was about the size
dinosaurs may have been
of a turkey.
warm blooded. Warmblooded animals include
birds and mammals. If dinosaurs were
warm blooded, then they would have been able
to adapt to changes in temperature. For coldblooded animals, such as frogs, lizards, and snakes,
the temperature of their blood changes with the
temperature of their surroundings, so they can easily
get too hot or too cold.

It would take five school buses lined up end-to-end
to equal the length of Seismosaurus!

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15


Recent discoveries have led scientists to change
their minds about how dinosaurs behaved.
Paleontologists once thought that dinosaurs did
not form groups or care for their young. However, a
set of newly discovered fossil footprints shows that

some dinosaurs lived in groups and took care of their
young.
These footprints were found in Colorado and Texas.
They show both small and large footprints made by the
Apatosaurus. The prints seem to show that parents and
young dinosaurs traveled together.

Sue Revisited
Computer images of the inside of Sue’s skull show
very large olfactory bulbs. These bulbs control an
animal’s sense of smell. Scientists used to think that
Tyrannosaurus rex had a poor sense of smell. But the
images suggest Sue had a good one!
Most scientists believe that Tyrannosaurus rex was
mainly a hunter. But this new information suggests
that it might also have been a scavenger. Scavengers
are animals that eat dead and decaying creatures.
So did Sue spend most of her time hunting or
scavenging? New information often presents more
questions than answers!

Apatosaurus lived in what is now Colorado and Texas.

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17


In 1985 many dinosaur bones were found in Alaska.

Most dinosaurs lived in hot climates, but new
discoveries have shown that this wasn’t true of all
dinosaurs. In 1985 fossils of eight types of dinosaurs
were found in Alaska. Alaska is very cold today, so
scientists wondered how dinosaurs could survive
there. However, when they studied the fossils of
plants as well as of dinosaurs, they discovered that
Alaska was much warmer millions of years ago.
There are still some questions. Though Alaska was
warmer then than it is today, it was still cooler than
places where most dinosaurs lived. Scientists are still
trying to find out how Alaska’s dinosaurs adapted.

What Happened to
the Dinosaurs?
There are several theories about what caused
dinosaurs’ extinction. At different times scientists
thought that volcanic eruptions, diseases, or a
gradual cooling of Earth might have been the cause.
Now, however, most scientists believe that the
effects from a huge asteroid hitting Earth caused the
dinosaurs to become extinct.
You’ve now learned about how paleontology
works and what paleontologists do. You’ve also read
about the new ideas that have developed as new
dinosaur fossils have been found. One thing is for
sure: We will keep learning more about dinosaurs as
scientists find more dinosaur fossils!

A huge asteroid hitting Earth may have been

responsible for the extinction of dinosaurs.

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19


Glossary
Vocabulary
erected
erected
v. to have been
put up straight; to have
setfoundations
upright
foundation n. the part on
mold
which
the other parts rest
for support; base

occasion
mold
n. a hollow shape
that you pour soft or
liquid
material into that
proportion
gives its shape to the
hardened

tidiedmaterial

Reader Response
occasion n. a particular
time
proportion n. a proper
relation between parts
tidied v. to have put in
order; to have made neat

Fact

Opinion

workshop n. a building or
area where work is done

workshop
Word count: 1,597

Note: The total word count includes words in the running text and headings only.
Numerals and words in chapter titles, captions, labels, diagrams, charts, graphs,
sidebars, and extra features are not included.

20

1. Using a graphic organizer like the one below, record
three facts about dinosaurs in the left-hand column.
Then write your opinion of this information in the
right-hand column.

2. What do you think paleontologists will do in the
future? On what facts are you basing your prediction?
3. What are some things you can think of, other than
dinosaur replica bones, that might be made in a
mold?
4. What question would you most like to ask a
paleontologist? Why?