Have you ever really looked at a bird’s feet?
Most birds have clawed toes and scales covering
their feet. Birds also lay eggs in nests. These
three traits are found in reptiles as well.
However, birds have many other traits, such
as feathers and warm-bloodedness,
that are not found in modern reptiles. One
of the most famous fossils ever found is Archaeopteryx, a
small animal with clawed toes, scaly legs,
teeth, and feathered wings. Archaeopteryx was
found in rocks dating from the Jurassic Period,
150 million years ago. Many scientists classify Archaeopteryx as
a bird. Other scientists point out that, if
you took away the feathers, this fossil would
look just like Deinonychus, a small
theropod dinosaur. Scientists agree that Archaeopteryx wasn’t
able to fly, partly because it had a flat sternum
(breastbone). Birds have a keeled sternum to
which flight muscles are attached. Yet Archaeopteryx clearly
had feathers. Was this fossil a dinosaur or
a bird? This is only one of the many questions
paleontologists struggle with when they study
the evolution of birds.
One of the first people to make a connection
between dinosaurs and birds was Thomas Huxley,
a contemporary of Charles Darwin in the 1800s.
In 1916, a Danish doctor named Heilmann wrote
a book titled The Origin of Birds, in
which he listed the similarities between the
skeletons of theropod dinosaurs and modern
birds. Later fossil discoveries made these
similarities more striking. In the 1960s, an
American named John Ostrom found 22 features
in theropods and birds that could not be found
in any other animal groups. However, new fossils
of birds and birdlike dinosaurs are being discovered
every year. Some of these fossils are changing
perceptions of the origins of birds. Did birds
evolve from theropods or another group of dinosaurs?
Or did birds and dinosaurs evolve from a common
ancestor much earlier in geologic time? Is Archaeopteryx the
first bird? When did feathers evolve and how?
Which came first, feathers or flight? These
are some of the questions you will explore
in this WebQuest.
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Your job in this WebQuest is to form an opinion
as to the origins of birds. You will have to
find out what evidence supports the theory
that birds descended from theropod dinosaurs.
You will have to identify the similarities
among birds and other groups of animals. You
will also learn about new fossils that provide
additional information about the evolution
of birds. You will prepare a table in which
you compare and contrast several fossils that
may, or may not, be links in the evolutionary
history of birds. Finally, you will use the
information from your Internet research and
the table you have prepared to answer the following
question: are birds really dinosaurs?
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Look at the web sites given here to find the
information that will enable you to make an
informed decision about the origin of birds.
- Archaeopteryx:
An Early Bird. Visit this site
to learn about fossils of Archaeopteryx, a
150-million-year-old fossil from Germany.
You can find out why fossils of Archaeopteryx provide
strong phylogenetic links between birds
and reptiles.
- Aves:
Fossil Record. Visit this site
by the Museum of Paleontology, University
of California, Berkeley to learn about
the fossil record of birds. At this site
you can find out about a new bird fossil
found in China and how it compares to Archaeopteryx, a
fossil of nearly the same age.
- Are
Birds Really Dinosaurs? At this
DinoBuzz site you can learn about the
evidence that supports the theory that
birds are theropod dinosaurs. You can
read about why most scientists accept
the idea that birds and dinosaurs are
related, based on phylogeny and cladistics.
- Dinosaurs
and Birds: The Story. Visit this
excellent site for an interesting description
of systematics, the science of evolutionary
relationships. This site discusses how
scientists identify evolutionary relationships
among groups of organisms such as dinosaurs
and birds. The site includes a good history
of thoughts on bird evolution, and some
evidence that shows that birds are not
descended from dinosaurs.
- Feathers,
scutes, and the origin of birds. Visit
this site to read an interesting article
about the relationships among dinosaurs
and birds. The author discusses new findings
that show how scutes, a type of scale
seen in crocodiles and on bird feet,
can develop into feathers.
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2 class periods; a total of 60 minutes for
Internet research, 20 minutes to prepare table
and answer question
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Now that you have completed your research
on the Internet, prepare a table that lists
the bird and/or birdlike dinosaur fossils that
provide some evidence of the origins of birds.
In the left column, write the genus names of
the fossils you have studied. At the top of
the rows, write in the age of the fossil, where
it was found, and why it is important to the
study of bird evolution. The table is started
for you below.
Table 1. Origins of Birds
Name
of Fossil |
Age
(millions of years)
|
Location |
Important
Facts |
Longisquama |
220 |
Kyrgyzstan |
was an
archosaur, a type of reptile; was neither
a bird nor a dinosaur; had complex
set of feathers and a furcula (wishbone)
- both bird characteristics |
Archaeopteryx |
150 |
Germany |
has clawed
toes, scaly feet, wings, feathers (bird
characteristics); has teeth, flat sternum
(reptile characteristics)
|
| |
|
|
|
Once you have completed the table with information
gathered from the Internet, you should be able
to answer the question: are birds really dinosaurs?
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In the process of completing this WebQuest,
you’ve become informed about the evidence linking
birds with dinosaurs, and about new fossil
discoveries that challenge the theory that
birds evolved from theropods. You have developed
critical thinking skills and you have explored
the many different facts that relate to the
question of the origins of birds. You have
read information to complete a table about
bird and birdlike fossils, and formed an educated
opinion as to the origins of birds. Are birds
really dinosaurs?
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