Lab12: Making and Interpreting Dinosaur Footprints


Alexander's method is used to calculate the speed of an animal from itís footprints, when the time taken to make the tracks is unknown. We will use this method, as well as conventional velocity measurements, on the tracks of a (hopefully cooperative) chicken. We will also reconstruct the anatomy of a trackmaker's feet from footprints.
 

PART 1. HUMAN LOCOMOTION

Selected students will walk and run along a length of hallway. The number of strides taken will be noted (a stride is the distance from a homologous part of one footstep of one foot to the next footstep of the same foot) as well as the total distince traversed, and the amount of time the traverse takes. Do it for walking and running.

1.  Actual velocity of the student

Measure the veocity of the student during its traverse (i. e. measure the distance the student walks and the time it takes).

V = d/t

where:

V = velocity (m/s)
d = distance traveled (m)
t = time (s)

 2. Velocity estimated from the footprint length and stride length.

We will assume the footprint length would equal the student's foot length.

Use Alexander's formula to calculate the predicted velocity of the student:
where:

DS = dimensionless speed
L = leg length (m)
g = gravitational acceleration (= 10 m/s2)

 Get dimensionless speed from the graph (Figure 1) or use this equation:
DS = (RSL x 0.83) - 0.7
where:

1. RSL (relative stride length) = (stride length)/(hip height)
2. hip height (= leg length) = 4 x (foot length)
 

 Compare the real person with the assumption that "hip height (= leg length) = 4 x (foot length)"


PART 2. DINOSAUR TRACKS

The TA and the class will prepare a bed of clay on which the theropod dinosaur (Gallus gallus - domestic chicken) will walk. The chicken encouraged to walk or if we are lucky, run along the clay. The amount of time the checken takes to traverse the clay bed will be timed with a stopwatch, and the length of the traverse from homologous points on the first and last track will be measured .

1. Actual velocity of the chicken
 

Measure the veocity of the chicken during its traverse (i. e. measure the distance the chicken walks and the time it takes) as you did for the student above.


2. Velocity estimated from the footprint length and stride length.

Use Alexander's formula to calculate the predicted velocity of the chicken as you did for the human.


3. Compare calculated speed with real speed.

Are they different and why?

PART 3. DINOSAURIAN SPEEDS

1. Use the outline drawing (Figure 2) to calculate the speeds (in meters/sec) of the dinosaur tracks using the same methods as above. Compare these speed estimates with those of the chicken. The track type here is a small theropod track called Grallator.


PART 4. RECONSTRUCTING TRACKMAKERS FEET

1. Look at the dinosaur footprints we have out and draw the outlines taking special care to accurately draw in the position of the foot pads. Using Peabody's method (Figure 3), which states that the pads of the track correspond to the joints between the bones (phalanges), reconstruct the foot skeletons of Anchisauripus sp. and Anomoepus sp. By comparison with the Allosaurus skeleton, label the digit numbers, and determine whether the tracks are left or right (remember these tracks are casts, not impressions). Which do you think is ornithischian vs. saurischian?

2. Draw the footprint of Gallus gallus and reconstruct its anatomy. Compare with the other dinosaur tracks.