Hi,
I'm currently using Alexander's 1976 formulae to determine dinosaur speeds from trackways.
The trackway I have in question is 11 tracks long. To determine the speed, do I use the formula on each set of prints and their stride, or just the one set?
Thank you,
Danny.
You could measure the stride length for each step cycle - 3 consecutive imprints (or sets of manual + pedal imprints in case of quadruped animals) = 1 step cycle, 11 imprints = 9 step cycles - and then do an averaging over all step cycles (mean stride length).
If the trackway pattern shows considerable variation (e.g. curves) you should rather calculate distinct velocities for different parts of the trackway and discuss that.
I guess Michael's suggestion of using a mean stride length in rather homogeneous track is a good advice.
However I do question if using Alexander's famous equation from 1976 is the best take on speed estimates.
The factor of 4 times the foot length for the height of the hip is not as uniform among upright walking vertebrates as Alexander thought. The first to question this was Thulborn (e.g. Thulborn, R.A. 1989, The Gaits of Dinosaurs. pp. 39-50 in Gilette, D.D. And Lockley, M.G. (eds.) Dinosaur Tracks and Traces.). More recently there were studies that showed an even wider range of “hip height to foot length” ratios (e.g. This poster: http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDsQFjAD&url=http%3A%2F%2Fphobos.ramapo.edu%2F~erainfor%2Fpubs%2FManzellaECSCposter.pdf&ei=FylIVKSRHImCzAPevYC4Bg&usg=AFQjCNEFpOhqyIPn5jajrLvVZ-g-wxEU5w&bvm=bv.77880786,d.bGQ&cad=rja).
Even more fundamental critique derives from the difference in limb kinematics between dinosaurs and mammals (which were ultimately used by Alexander to derive his equation). (I remember a talk about this by Heinrich Mallison at Symposion about sauropod giantism at the centenary meting of the Paläontologis the Gesellschaft in 2012, but all I could find on a fast search in the internet is the direct predecessor of the talk I ramember; a talk at the SVP meetin in November 2011: http://dinosaurpalaeo.wordpress.com/2011/11/10/my-svp-talk-fast-forward-dinosaurs-part-1/)
So Alexander's equation may not be best solution. But if you want to use it take Michael's advice and use a mean stride length if applicable.
http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDsQFjAD&url=http%3A%2F%2Fphobos.ramapo.edu%2F~erainfor%2Fpubs%2FManzellaECSCposter.pdf&ei=FylIVKSRHImCzAPevYC4Bg&usg=AFQjCNEFpOhqyIPn5jajrLvVZ-g-wxEU5w&bvm=bv.77880786,d.bGQ&cad=rja
http://dinosaurpalaeo.wordpress.com/2011/11/10/my-svp-talk-fast-forward-dinosaurs-part-1/
I myself have no expertise in this field at all, but I suggest you make contact with Donald Henderson at the Royal Tyrell Museum in Canada. I have once known him personally and back then he did excellent work on reconstructing gaits, speeds, and biomechanics of dinosaurs. He could certainly tell you some interesting stuff.
A recent paper suggested a simpler formula than Alexander's, at least based on empirical measures of humans running on different substrates. I haven't seen it applied elsewhere yet so not sure if people think it will apply to dinosaurs:
Ruiz, J. and Torices, A. 2013. Humans running at stadiums and beaches and the accuracy of speed estimations from fossil trackways. Ichnos 20: 31-35.
DOI:10.1080/10420940.2012.759115
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