The Origins of Birds

Introduction

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 was not 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 those of 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. Task

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 questions you have answered to write a letter to the editor of a paleontology magazine. In your letter, you will present your opinion to the question: are birds really dinosaurs?

Process

Use the resources listed below to help you complete your research. Keep in mind that not all Web sites are written specifically for students. Some of what you read might be challenging. Look for information that will be useful in completing this WebQuest. Answer the following questions to help with your project.

1. What are some features of dinosaurs that have lead scientists to theorize that birds evolved from dinosaurs?

2. Why are bones often studied when trying to determine the origins of birds?

3. What are some differences between birds and dinosaurs?

4. If birds are not descendants of dinosaurs, what have scientists proposed they may have descended from?

5. Were all dinosaurs with feathers able to fly?

Once you have answered the questions with information gathered from the Internet, you will prepare your letter to the editor answering the question: are birds really dinosaurs? Your goal is to convince the readers of the magazine to agree with you. Keep your audience in mind. The readers of the paleontology magazine are other paleontologists, so you will have to support your opinion with lots of scientific evidence.

Resources

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.

Dinosaurs Grow Up http://www.sciencenewsforkids.org/articles/20031126/Feature1.asp

The Origin and Early Evolution of Birds http://www.geologyrocks.co.uk/tutorials/origin_and_early_evolution_birds

Origin and Evolution http://www.thewildclassroom.com/biodiversity/birds/aviantopics/originandevolution.html

Archaeopteryx: An Early Bird http://www.ucmp.berkeley.edu/diapsids/birds/archaeopteryx.html

Aves: Fossil Record http://www.ucmp.berkeley.edu/diapsids/birds/birdfr.html

Are Birds Really Dinosaurs? http://www.ucmp.berkeley.edu/diapsids/avians.html

Dinosaurs and Birds: The Story. http://www.abc.net.au/science/slab/dinobird/story.htm

Fossils from China Link Birds with Dinosaurs http://www.nationalgeographic.com/society/ngo/events/98/dinosaurs/index.html

Scientists: Fossils prove that birds evolved from dinosaurs. http://archives.cnn.com/2002/TECH/science/03/06/feathered.dinosaur/index.html

Feathers, scutes and the origin of birds http://www.dinosauria.com/jdp/archie/scutes.htm

Evaluation Read this rubric to determine how you will be scored in this WebQuest.

Criteria Points 1 2 3 4 Task The task was It appears that The task was The task was not completed. some effort was completed as completed with made to assigned, but great attention complete the some of the to detail and task, but major information was thorough ideas are faulty. documentation. missing. Process The process The research All the steps of It is clear that was not was complete, the process much effort followed. but the table were followed went into the and letter could and the table project. The have been was good. table contains better several fossils organized. and facts. Letter Letter was not Letter was well Letter was well Letter was completed, or it researched but thought out and organized and appeared that lacked some included arguments little effort went key features arguments that were well into the project. needed for were clearly supported. It is accomplishing supported by evident that the task. research. much research went into the project.

Conclusion

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. You also presented and supported your opinion with scientific evidence.