GEOS 106 – LIFE IN THE AGE OF DINOSAURS
LAB – FLIGHT OF THE THEROPODS
Introduction
One of the most fascinating and important concepts to have emerged from the study of
dinosaurs in the last 20 years is the realization that the closest living relatives of
dinosaurs are birds. Moreover, birds share a number of startling similarities in their
skeletal anatomy with one group of carnivorous dinosaurs known as theropods. In fact,
we now can state with a high degree of certainty that BIRDS ARE DINOSAURS.
1. How and why do believe this to be true?
2. What specific features of the skeleton do birds share with theropods?
3. Did these features all arise suddenly in the fossil record, or were they acquired
gradually?
4. What, exactly, is a bird?
In this lab, we will investigate these questions by examining the skeletons of a theropod,
a modern bird, and the exceptional fossil form, Archaeopteryx. We will then map the
acquisition of avian characters onto a cladogram of dinosaurs.
Learning Goals:
 To understand the similarities between a bird and theropod dinosaur
 To learn how we collect data for paleontological studies
 To recognize the importance of transitional forms in the fossil record
 To understand how cladograms are used to reveal evolutionary pattern
Upon completion of this lab, students will be able to:
 Identify key skeletal elements of a bird and theropod skeleton
 Map characters onto a cladogram
 Trace the acquisition of avian characters in the lineage leading to birds
Activities
Students will begin by learning the basic skeletal anatomy of a bird and theropod
dinosaur using the skeletons, individual bones, and figures provided. Students will then
locate these same bones and structures on a high quality reproduction of the primitive
bird, Archaeopteryx. Finally, data collected from these taxa will then be mapped onto a
cladogram showing the relationships of derived theropod taxa.
When talking about the “dinosaur-to-bird” transition it is necessary to be clear to which
group we are referring. Thus, we make the distinction of “non-avian dinosaurs” when
referring to the traditional concept of dinosaurs familiar to all kids, and “aviandinosaurs” when talking about the familiar concept of birds.
Before we can trace the changes that occurred on the dinosaur lineage leading to birds,
we need to learn some of the important skeletal features of birds and non-avian dinosaurs.
I. LIVING AVIAN-DINOSAUR (BIRD) SKELETON
Most people have eaten chicken or turkey, but did you ever pay attention to the bones?
Here we will learn some of the basic bones and structures of the avian skeleton.
Materials:
 mounted chicken or pigeon skeleton
 disarticulated skeleton of an ostrich
 isolated bird bones
 labeled illustrations of a bird skeleton
Using the materials provided, locate and identify the following bones or structures:
1.
2.
3.
4.
5.
6.
7.
8.
scapula
humerus
radius and ulna
carpometacarpus (fused metacarpals
+ carpals)
digits I, II, and III of wing
furcula (wishbone)
keeled sternum
synsacrum
9. pygostyle (fused tail vertebrae)
10. tibiotarsus (fused tibia + tarsals)
11. fibula
12. tarsometatarsus (fused metatarsals +
tarsals)
13. digits I-IV of foot
14. hallux (reversed toe for grasping
branch)
We are familiar with birds having light, hollow bones. Many avian bones are
pneumatic, and are invaded by air sacs used in breathing.
II. NON-AVIAN THEROPOD DINOSAURS (VELOCIRAPTOR AND KIN)
Now lets get to know some of the most famous dinosaurs – carnivorous theropods.
Materials:
 Deinonychus foot
 cast of theropod skeleton
 Velociraptor skull
 T. rex furcula
 various theropod bones
 illustrations of various theropod taxa
Using the materials provided, locate and identify the following bones or structures:
1.
2.
3.
4.
5.
antorbital fenestra
pleurocoel on vertebra
humerus
radius and ulna
digits I, II, and III of hand
III. SKELETON OF ARCHAEOPTERYX
6.
7.
8.
9.
furcula
tibia and fibula
digits I-IV of foot
hollow bone
Archaeopteryx is an excellent example of a transitional form in the fossil record. The
first fossils of Archaeopteryx, found in Germany in the late 1800s, would have been
attributed to a non-avian dinosaur – if there hadn’t been feather impression found with it!
Today, Archaeopteryx is still considered the oldest definitive fossil bird (Late Jurassic,
about 150 Ma).
Materials:
 cast of Berlin specimen of Archaeopteryx
 labeled illustrations of Archaeopteryx
 model of Archaeopteryx skull
Using the materials provided, locate and identify the following bones or structures:
1.
2.
3.
4.
5.
antorbital fenestra
scapula
humerus
radius and ulna
digits I, II, and III of hand
6. tibia and fibula
7. digits I-IV of foot
8. feathers
IV. AVIAN CHARACTER ACQUISITION IN BIRDS
In Lab 3 we learned how a cladogram is constructed. Essentially, it is a map of character
distributions among different types of organisms. The cladogram provided here was
generated using hundreds of characters from all parts of the skeleton. Onto this
cladogram we will add various characters where they are likely to have arisen – we will
map characters. To do this, you will mark the character along an internode (a branch
between splits) only once, at the lowest point on the cladogram possible.
For example, consider the character “hollow bones”. If you know that hollow (or
pneumatic) bones are found in the pigeon, Velociraptor, T. rex, and ceratosaurs, then you
would place a mark on the internode between “Dinosauria” and “Theropoda”. Thus,
hollow bones are a synapomorphy (a shared, derived character) of Theropoda.
If you are uncertain were to place a character due to its absence in some of the taxa (a
common problem for paleontologists) then put it as low as possible, and put a “?” by it.
Several characters may belong along a single internode.
Character list:
1. antorbital fenestra
2. enlarged braincase
3. absence of teeth
4. humerus as long, or longer than
scapula
5. ulna as long, or longer, than the
femur
6. three-fingered hand
7. carpometacarpus
8. greatly elongated grasping hand
9. furcula
10. flat sternum
11. keeled sternum
12. reduced fibula
13. tarsometatarsus
14. backwardly pointing toe
15. fully reversed hallux
16. pygostyle
What about feathers?
Feathers have long been thought of as a hallmark characteristic of birds, and only birds.
In the past 15 years new discoveries of feathered animals have been found in China, in
rocks of Early Cretaceous age (124 Ma). If we ignore the feathers that are covering their
body, we discover that they are “good” dinosaurs, and include forms such as
Sinosauropteryx and Microraptor (shown on your cladogram). Now map the character
“feathers” onto the cladogram.
Questions:
1. Cladograms can be predictive. Did you observe a furcula in Archaeopteryx?
Would you predict it has one? Why?
2. In living birds many of the bones we looked at were fused together, such as the
carpometacarpus and synsacrum. Why do you think this is the case?
3. Skeletons of most dromaeosaurs (including Velociraptor) have never been found
with feathers. However, the dromaeosaur Microraptor does have feathers. What
does this suggest about Velociraptor?
4. Lets pretend a new dinosaur species is discovered and it is a close relative of
Allosaurus. As a famous artist, you have been commissioned to paint a life-like
reconstruction of it. How would you depict its integument (body covering)?
5. If an animal possesses feathers, it does not mean it can fly. Provide at least two
reasons why feather may have been advantageous for an organism before flight
evolved.
Relationships among theropod dinosaurs, including birds.