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Studying Fossils

Dinosaur Tracks: From Stride to Leg Length to Speed

Authors: Maryann Buehler and Amy Quillen
Woodrow Wilson Biology Institute
1995

Target age or
ability group:
High school biology and Physical science
Class time
required:
2-3 class periods
Materials and
equipment:
Required Texts:
Dynamics of Dinosaurs and Other Extinct Giants. (R. McNeill Alexander, Columbia University Press, 1989) Dinosaur Tracks. (Tony Thulborn, Chapman and Hall, 1990).
Stride Measurements: meter stick, chalk.
Speed Measurements: stop watches.
Graphing: graph paper, calculators, pencils, erasers.
Lecture: transparencies, overhead projector.
Summary of
activity:
During this series of activities, students will determine the relationship between leg length, stride length, and speed in humans and bipedal dinosaurs. Data will be collected and graphed for these human characteristics and analysis of the graphs will show that (1) the longer the leg length, the greater the stride and (2) the greater the relative stride, the greater the speed. These conclusions can be transferred to dinosaur leg length, stride length, and speed since these dinosaurs walked with their feet well under the body like modern mammals and birds. Students will use actual data collected from dinosaur track pads and fossils to interpolate the speed data for bipedal dinosaurs.
Prior
knowledge,
concepts or
vocabulary
necessary to
complete activity:
metric measurement, x-y scatter graphing, algebra I, stride length, relative stride length, speed, leg anatomy, bipedal, interpolation, paleontology.

Teacher Instructions

Background
For paleontologists to estimate speed of dinosaurs, they must first understand what affects the speed of modern mammals and birds. This assumption follows the theory of uniformitarianism, which states that the present is the key to the past. After systematically working out the relationship between leg length, stride length, and speed of mammals and birds (Figure 3.8, p. 36, of Alexander's Dynamics of Dinosaurs and Other Extinct Giants), students can then use their measurements of dinosaur tracks and fossil lengths to determine speed data for dinosaurs. To simplify the analysis, use Alexander's graph (Figure 3.10, p. 38) that shows the relative relationship between speed and stride for many mammals and birds. If there is time, the teacher, can plot the dinosaur data on the graph by using the following formula:

dimensionless speed = speed / (leg length X gravitational acceleration)1/2

Calculations are provided below under Part 2 and 3 of Sequence of Events, Part B.

Sequence of Events / Part A. Introduction

Lecture
Using figures from Thulborn's Dinosaur Tracks, briefly introduce the principle types of trace fossils (Figure 1.1, p. 5). Explain the process by which dinosaur tracks are formed and preserved (Figure 2.1, p. 15) and show some traced track pads (Figure 6.3 p. 148 ).

Think/Pair/Share (TPS)
Ask students to think and write about the following question: How could a paleontologist determine the speed of a dinosaur? Then tell them to pair with a partner to discuss their ideas.

Class Idea Collection
Collect group ideas on the chalkboard.

Part 1

Cooperative Group Work
Determining human stride. Combine every two TPS groups into a group of four and explain to students that they need to design a set of methods to determine average stride for each person in their group. Remind them that their data will be eventually presented in a table and graphed and elicit their ideas on how to get a reasonable average measurement. Suggest taking three measurements per person and averaging.

Why variation In strides?
After students collect stride data, ask them why the strides vary in their group? In other words, what affects stride length?

Lecture
Explain to the group how height is measured in dinosaur fossils (Figure 8.4, p. 248) and ask them to take a similar measurement on themselves. Take some time to explain to them where their hip joint is by using a picture of a skeleton and demonstrating on yourself. Have students hypothesize what the relationship would be between stride and leg length.

Part 2 and 3

Cooperative Group Work
Determining hip to ground measurement and average speed. Send students out again this time with a meter stick, stopwatch, and chalk to determine the average speed and hip to ground length for each person in group. When they return, have them put their data on the board.

Graphing
Ask students to make a graph of stride length vs. height and stride length vs. average speed for the class.

Lecture
After graphs are completed, compare stride length vs. speed for dog, camels, and humans (Alexander's Figure 3.10, p. 38). Explain that in order to get a more consistent relationship with different sized animals it is important to look at relative relationships. For example:

Relative Stride = (Stride Length/Leg Length) for each animal,
and
Dimensionless Speed = Speed/(Leg Length X Gravitational Acceleration)1/2

Explain also that the reason why they are using mammal and bird data is because of the similarity in walking styles as opposed to reptiles (Alexander's Figure 3.5, p. 32).

Show Figure 3.10 (p. 38 Alexander), which depicts a consistent relationship between speed and stride length of mammals and birds. If there's time, plot dinosaur data onto this graph. The dinosaur data is given below:

Dimensionless Speed

Relative Stride Length

Bipedal Dinosaur

0.44

1.4

Bipedal Dinosaur

0.49

1.5

Bipedal Dinosaur

1.14

2.5

Bipedal Dinosaur

0.62

1.7

Lecture
Explain how track pad data equals the distance from one footprint to the same point on the next print of the same foot (Figure 6.3 p. Thulborn).

Individual Work
Give each student a copy of Graph 1 (dinosaur relative stride vs. speed) and Table 1 (dinosaur length of leg, stride length, etc.) and ask them to use the dinosaur stride length (SL) and height (h) to calculate the relative stride. Then ask students to use Graph 1 to interpolate their data to determine speed.

Dinosaur Tracks:
From Stride to Leg Length to Speed

Student Instructions

Introduction
Dinosaurs became extinct long ago, but the tracks they have left can give us clues to their size and speed. In this activity you will deal with bipedal dinosaurs, those that walk on two legs. You will first determine if there is a relationship between the length of your leg and the length of your stride. Later you will apply what you know to dinosaurs.

Part 1

Dinosaurs left trackways in muddy areas that provide us with a series of footprints from which we can determine stride length. However, you may not want to go to the trouble of walking through the mud to leave your own trackway.

1.As a group, determine another way that you can measure each other's stride.

2.Once you have determined your method, measure and record the stride length of each of the members of your group.

Question 1. What variables affected peoples stride length?

Question 2. Did taller students have a longer stride?

3.Make a hypothesis concerning the relationship between height and stride.

  • Let's be scientific and see if we can collect some data to support your hypothesis. To measure the leg length of your group members you must measure their leg from their hip bone to their ankle bone. (Refer to a drawing or a model of the human skeleton to see where the hip bone is located.)

4.Make the leg measurements for all your group members and record.

  • Now it's time to make some sense of the data. To see a clear relationship between leg and stride length, you need a larger sample size (more people). Record both measurements for each group member on the chart that your teacher has provided on the board. Record all the class data in the chart (worksheet) your teacher has provided. Graph these data.

Question 3.Is there a relationship between leg length and stride length? Describe that relationship.

Question 4.What other characteristics can be determined by looking at stride?

Part 2

How does your leg length affect your speed?

Design a set of methods to determine the speed of each member of your group. You will be given a stop watch, a meter stick and a piece of chalk as materials.

Remember to record all data carefully and be as exact in your measurements as you can.

Again collect the data from all of your classmates.

Question 5.Describe the relationship between leg length and speed.

Part 3

Does the length of your stride affect your speed?

Now, graph the class data to determine the relationship of stride length and speed.

Question 6.Describe the relationship between stride length and speed.

Part 4

Dino Data

Now that you have established a relationship between your class's average leg length, stride length and speed, let's look at some dinosaur data.

All of the following track-makers were bipedal dinosaurs (Table 10.1, p. 291, Thulborn).

On to Its All In The Rocks
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