echoesof.science · Ages 15–16
Reading trackways: dinosaur speed, evidence and uncertainty
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the game and the quiz
echoesof.science/school/dinosaurs/ages-15-16/
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Dinosauria can be defined by ancestry: the group descended from the most recent common ancestor of Diplodocus, Triceratops and the house sparrow. That makes birds dinosaurs; palaeontologists say 'non-avian dinosaurs' for the rest.
Anatomy: all dinosaurs held their limbs directly under the body, with hinge-like ankles. They are split into ornithischians and saurischians by hip structure. Pterosaurs, marine reptiles and crocodiles are not dinosaurs.
Trackways record movement. The stride length λ is the distance between two prints of the same foot, and the hip height h is often estimated as about 4 × the footprint length.
Experiment: Testing Alexander's equation on yourselves
- Measure your hip height h (floor to the top of the thigh bone at the side of the hip) in metres. Also measure your foot length and compare h with 4 × foot length.
- Mark a 10 m timing zone in the middle of the track, with a run-up before it.
- Walk through the zone at a steady pace. A partner times you over the 10 m; another marks where the heel of the same foot lands twice in a row. Measure the stride length λ.
- Measured speed = 10 m ÷ time. Predicted speed u = 0.25 × √9.81 × λ^1.67 × h^−1.17.
- Repeat for a fast walk and a gentle jog. Do three trials of each and take means.
- Calculate the percentage difference between predicted and measured speed, and estimate the uncertainty in each measurement.
| Trial | h (m) | λ (m) | Time for 10 m (s) | Measured speed (m/s) | Predicted u (m/s) | Difference (%) |
|---|---|---|---|---|---|---|
| Walk | ||||||
| Fast walk | ||||||
| Jog |
Questions
From your results, calculate the percentage difference between predicted and measured speed for each trial, with an uncertainty. Was the equation better for walking or for jogging?
List three reasons why a speed calculated from a fossil trackway may be wrong.
Explain why scientists say 'non-avian dinosaurs' when they talk about the extinction 66 million years ago.
Sketch a trackway of four prints and label the footprint length, the stride length λ and how you would estimate h.
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Sources for every fact on this sheet: echoesof.science/school/dinosaurs/sources/