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The Dinosaur Skeleton
Objectives:
1. To learn the names of the bones of a vertebrate skeleton.
2. To be able to describe the differences between different dinosaur groups using
skeletal terminology.
3. To be able to identify dinosaur bones as they are excavated.
Procedures:
Much of what we know about dinosaurs comes from the study of their bones. The
similarity of the skeletons of various dinosaurs and humans is based on the common
ancestry of all vertebrates (the subphylum of animals with an internal bony skeleton).
We refer to the similarity in structures that is the result of evolutionary descent as a
homology. Homologous structures need not have similar functions. For example, the
wing of a bird and the arm of a human are homologous but do not have the same
function. Structures with similar functions are called analogous structures.
The Appendicular Skeleton (arms and legs)
Examine the labeled skeleton of a human and the Camarasaurus. The dinosaur
forelimb is essentially the same as our forelimb with one exception; we do not have a
separate coracoid, a round bone between the scapula and humerus.
The bones of the dinosaur hindlimb are comparable to the human leg. The primary
difference between dinosaurs and humans is the ankle. Dinosaurs have two small bones
the astralgalus and the calcaneum between the tibia and fibula and tarsal bones, whereas
the humans do not have these bones. Don’t worry; we will not see these on the diagrams.
The axial skeleton (skull, vertebra, ribs, and pelvis)
The dinosaur skull is usually cited as evidence that dinosaurs are reptiles. Humans
have a typical mammalian skull. The dinosaur skull is divided into several bones that are
separate from each other while many of these bones in the human are fused. This is
illustrated with the lower jaw or more correctly called the mandible. In humans, our jaw
consists of one bone, while a dinosaur’s mandible is often divided into five bones.
Another major difference is the hinge of a dinosaur jaw. Notice how the hinge of a
dinosaur’s jaw is often at the back of the mandible and usually below the teeth. In
humans, the mandible hinge is well above the teeth. We will complete a separate
laboratory on the skull to see how this works.
The dinosaur pelvis is an important structure that enables us to identify the two major
groups of dinosaurs. The textbook, The Dinosaur Primer, shows the major bones of the
pelvis. Lizard-hipped dinosaurs (saurischian dinosaurs) have a pelvis with a 90º or less
angle between the pubis and ischium and the pubis has a large knob at the end. The birdhipped dinosaurs (ornithschian dinosaurs) have a pubis without the knob and it pubis
oriented backwards resulting in a long pubis with a forward prong and a backward prong.
In humans the bones of the pelvis are fused, but the individual bones are still identifiable.
The vertebral column is divided into four regions, cervical (between the skull and
scapula), back (between scapula and start of pelvis), sacral (vertebra between the two
halves of the pelvis), and tail.
Worksheet
This is a Styracosaurus skeleton. Answer the questions below.
Identify the labeled bones from the list.
1. Bone 1 is the
a. skull
b. mandible
c. humerus
d. femur
e. pelvis
2. Bone 2 is the
a. skull
b. mandible
c. humerus
d. femur
e. pelvis
3. Bone 3 is the
a. tibia
b. fibula
c. humerus
d. femur
e. rib
4. Bone 4 (in black) is the
a. tibia
b. fibula
c. humerus
d. femur
e. rib
5. Bone 5 is the
a. tibia
b. fibula
c. humerus
d. femur
e. rib
6. Bone 6 is the
a. tibia
b. fibula
c. humerus
d. scapula
e. rib
7. Bone 7 is the
a. tibia
b. vertebral column
c. humerus
d. scapula
e. rib
8. Bone 8 is the
a. tibia
b. vertebral column
c. humerus
d. ulna
e. radius
9. Bone 9 is the
a. caracoid
b. vertebral column
c. humerus
d. ulna
e. radius
Below is a diagram of a Camarasaurus skeleton. Answer the questions below about
the labeled sections.
10. “A” corresponds to the ___________ section of the skeleton
a. appendicular
b. cervical
c. tail
d. sacral
11. “D” corresponds to part of the ___________ section of the skeleton
a. appendicular
b. cervical
c. tail
d. sacral
e. dorsal
12. “B” corresponds to the ___________ section of the skeleton
a. appendicular
b. cervical
c. tail
d. sacral
e. back
Below is a photograph from Dinosaur National monument in Utah. Identify the labeled
bones below. (Hint: use the Camarasaurus diagram above question 10 to help you figure
it out.)
13. The bone labeled A is a
a. femur
b. scapula
c. humerus
d. skull
e. pelvis
14. The bone labeled B is a
a. femur
b. scapula
c. humerus
d. skull
e. pelvis
15. The bone labeled C is a
a. femur
b. scapula
c. humerus
d. vertebra
e. fibula
16. The bone labeled D is a
a. femur
b. scapula
c. humerus
d. skull
e. rib
17. The bone labeled E is a
a. femur
b. scapula
c. humerus
d. skull
e. pelvis
Compare this pelvis with figure 2.5 in A Dinosaur Primer. (Note the orientation may or
may not be reversed in this photo).
18. This is a ____________ pelvis.
A. saurischian
B. ornithschian
19. The bone labeled A in the pelvis is the
A. illium
B. pubis
C. ischium
20. The bone labeled C in the pelvis is the
A. illium
B. pubis
C. ischium
21. D is the
A. pubis
B. hip-socket or acetabulum
C. opening to the spinal cord
D. ischium