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## Tuesday, October 21, 2014

### Footprints and trackways

How do paleontologists and anthropologists use footprints and trackways?  Often, information is extrapolated from tracks and used to determine approximate heights and sizes of the organism that left the tracks.  How can this be?  Is there a correlation between foot size, leg length, stride length...and HEIGHT?  Let's find out!

These formulae don't only work for dinosaurs. If you like Lego, you may like to know that using Alexander and Thulborn's formulae, a Lego minifig (the little people) could walk at 0.5 km/h and run at 2.2 km/h
 Using the same equations that estimate dinosaurs' speeds, Lego figures could run at 2 km/h and walk at 0.5
(Lego info from http://www.csiro.au/helix/sciencemail/activities/dinospeed.html)

Where g is the acceleration from gravity. On Earth, g=9.8 m/s². Don't worry if you haven't come across maths like this before. What's important is that it's a way of estimating an animal's speed, without measuring it directly.
We can check Alexander's formula by comparing it to our measurements. The stride length is just the distance (100m) divided by the number of strides (half the number of steps). In terms of your measurements, Alexander's formula becomes:
Your actual speed is just the distance divided by the time it took:

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  (Source: http://www.ucmp.berkeley.edu/education/dynamic/session3/sess3_act2.htm)

#### What can a single track tell us?

Not too much. We can infer something about the size of the animal and maybe something about the sediment. We may have a clue as to who made the track.

#### What can a trackway (a series of tracks or footprints) tell you?

• Who was there.
• How many animals were there.
• The sizes of the animals compared to one another.
• How they were interacting - social activity, such as herds, moving in families, etc.
• How fast they were moving.
• What the sediment was like, and therefore something about the environment of the time.

Source of above text: http://www.ucmp.berkeley.edu/education/dynamic/session3/sess3_stories3.htm