Interpreting the Tracks
Brent Breithaupt and Judy Scotchmoor
Students will discover the relationships among foot length, leg
length, stride length and speed in bipedal animals. Data collected
and graphed for a student population will be applied to track data
from a research site in Wyoming to make inferences about dinosaur
physiology and behavior. Trackways provide direct data in the form
of foot length/size and stride length. These data can provide clues
about dinosaur speed.
6-8 or 9-12
- Make student packets (see materials).
- Prepare overheads (see materials).
Two to three class periods
groups of 3 or 4 and whole class
cm ruler and meter stick for each group of students
student packet - one/group, containing copies of the following:
- all student materials as needed
- reconstruction of theropod traversing ripple marks [PDF
- main groups of dinosaurs and their tracks [PDF
Note:all images in packets courtesy of Brent Beithaupt, The Geological
Museum, University of Wyoming
trace fossils, tracks, trackways, stride length, hip height, relative
speed, bipedal, quadrupedal, ripple marks
As trace fossils, tracks and trackways represent preserved activities
of animals in the past. Trackways provide direct data in the form
of foot length/size and stride length. These data can provide information
about the animals' physiology, speed, and behavior. However, interpretation
of the data is dependent on several factors, including whether the
animal was bipedal or quadrupedal, the size and weight of the animal,
how the foot was placed, how the animal stood, the number of digits,
the surface on which the animal was moving, and the preservation
of the tracks.
By studying the tracks and trackways made by living animals, scientists
have found sufficient consistency in the data to provide accurate
correlations between the trackway data and the size and speed of
the trackmaker. These same correlations can be applied to the tracks
and trackways of extinct animals, such as dinosaurs.
The basic measurement of a dinosaur footprint is its length, represented
as FL. The ratio of footprint length and hip height (h) is different
for different groups of dinosaurs, but generally the hip height
of a bipedal dinosaur is roughly four times the footprint length.
The speed can then be determined as relative speed, which is stride
length (SL), divided by hip height (h). Generally speaking, if the
SL/h <2.0, then the animal was walking; >2.9, the animal was running;
and between 2.0 and 2.9, the animal was trotting.1
The particular tracks and trackways used for this activity are
several of thousands found in the Lower Sundance formation of the
Middle Jurassic in Wyoming. The presence of ripple marks on the
trackway surface, coupled with trace fossils of burrows of marine
animals, have led to the interpretation that many individual theropod
dinosaurs of different sizes and ages were walking together across
ancient tidal flats. Thus trackways can provide information about
who was there, what they looked like, what they were doing, how
they were interacting, and what the paleoenvironment was like.
1. Wright, J.L. and B.H. Breithaupt. 2002. Walking in their footsteps
and what they left us: dinosaur tracks and traces. IN Scotchmoor,
J., D.A. Springer, B.H. Breithaupt, and A. R. Fiorillo (editors)
Dinosaurs - The Science behind the Stories. American Geological
Institute. Pp. 117-126.
You may want to precede this activity with an introduction into
interpreting tracks and trackways in order to differentiate between
observation and inference. There are several such tracks available
such as those at: http://www.ucmp.berkeley.edu/fosrec/Heindel3.html
Part I: Finding
1. Class discussion: Think/Pair/Share - Ask students to think and
write about what tracks and trackways can tell us.
2. The discussion may include questions such as these:
Where were the tracks found? This might provide clues as
to the trackmaker, i.e. 3-toed tracks found in rocks of the
Pliocene could not be dinosaurs!
Who was there? What are the clues that help you determine the
How fast were they moving? What are the factors involved in
speed? If you only have a series of footprints, how can you
determine speed? [Hint: If a dozen of you lined up outside,
somewhere safe and flat, and you each took 100 steps, would
you all cover the same distance? Why not? Leg length and stride
are important. But without the leg and only the track, how can
we figure out the leg length? Is there a relationship between
foot length and leg length?
3. Have students remove their shoes and measure their feet in cm.
Using a tape measure or meter stick, have students measure the distance
from their hips to the floor in cm. (Working in pairs is helpful.
Hip height should be measured to the point at which the ilium protrudes.)
Have each student determine the foot length (FL) to hip height (h)
Gather all class data.
On average, the FL:h = ~1:4 and this is generally true of all bipedal
4. If time, weather, and facilities allow, have students discover
the correlation between stride length and hip height as a determinant
of relative speed. This can be done by having each student walk
across a surface of sand and measure his or her stride length. Then
have students repeat the activity while running. [NOTE: make sure
that students measure a stride length from either a left to left
print or a right to right print. A single step is considered a pace,
not a stride.] If students divide their stride lengths by their
hip heights, they will get a relative speed ratio. By gathering
the class data, it will be clear that the SL/h while walking will
be much less than while running. If there is not time for this activity,
lead a discussion about the activity and inform students that scientists
have run similar experiments on numerous bipedal animals with the
following results: Generally speaking, if the SL/h <2.0, then the
animal was walking; >2.9, the animal was running; and between 2.0
and 2.9, the animal was trotting.
5. Class discussion: How can we apply this information to tracks
and trackways of animals in the past? What kinds of hypotheses can
Part II. Applying
6. Hand out the student packet and allow sufficient time for students
to interpret the data. Let them know that they will be presenting
their hypotheses and the evidence supporting their ideas to the
rest of the class.
Guide students as needed, but eventually students should:
study the tracks and determine that the tracks were made by
a bipedal animal.
describe the trackmaker - three-toed, bipedal animal.
notice that the tracks were found in rocks from the Middle
perhaps infer that the track was therefore made by a theropod
measure the length of the single footprint (FL) and multiply
by four to determine hip height(h).
determine the relative speed by dividing the stride length
(SL) by the hip height (h).
notice that there are numerous tracks of different sized individuals
all traveling together, probably walking.
7. Have student groups present their findings and hypotheses to
the rest of the class.
Discuss and compare.
8. Ask students what other information might be available from
9. Show the overhead of the theropod walking across the ripple
marks. Ask students to comment on the reconstruction. There is another
piece of information visible - the substrate on which we find the
tracks. In this particular case we see ripple marks on the trackway
surface. These coupled with trace fossils of burrows of marine animals
have led to the interpretation that the dinosaurs were walking together
across ancient tidal flats.
10. Class discussion to summarize how scientists use multiple lines
of evidence to interpret the past.
Form and function are closely related. Collect pictures of the
skeletons of several mammals. Have students place them into groups
according to how fast the animals can run. Then closely examine
the limb types and foot postures of the mammals. Introduce the terms:
Plantigrade - walking with the sole of the foot on
the ground, such as in humans or bears.
Digitigrade - walking with the heel and ankle raised
off the ground; the weight of the body is born by the digits only,
such as in an ostrich or cat.
Unguligrade - walking on the toe tips, such as in
a horse or deer.
Have students compare the length of the upper leg (femur) with
the length of the lower leg (tibia/fibula in the plantigrade; tibia/fibula
and metatarsals in the digitigrade; and tibia/fibula, metatarsals,
and phalanges in the unguligrade). As T. rex has an upper
to lower leg ratio rather similar to our own, this can lead to an
interesting discussion on just how fast T. rex was capable
More on the Fossil Record:
Return to: Lines of Evidence for Past Change
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