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RE: Bakker & whiptails - jog my memory please!

One of my questions regarding the supersonic sauropod tails regards the fraying you see in a bullwhip. The tip of a bullwhip travels so fast it breaks the sound barrier, true, but because it cracks so fast, the ends of the whip eventually begin to fray. Not only that, but a bullwhip is a continuous piece of material. <<<

The continuity of material is an interesting question. Of course, bullwhip continuity is really a matter of scale. The tissue that makes up the bullwhip is made of different layers, as well as individual cells. I bring this up, not because I think tht this data influences bullwhip motion, but because sauropod tails are so much larger. So from a mechanical point of view, those huge sauropod verts are going to be smaller in the context of a butt-whip. I'm not sure (and I don't think anybody's sure) what the maximum size is that individual mechanical units can have while still funtioning as a whip, although the study done by our fellow lister did simulate the length and inferred mobility of each vertebrae, so that's a start. Estimating mass and required muscle/tendon strength would provide some limits on what cannot be done with animal tissue. Masters project, anyone?
As for the frayed whip end. This isn't just a sternght of materials problem, because that fraying is actually intergral to releasing energy (in terms of sound) when the end breaks the sound barrier. Basically, the difference between a non-frayed and frayed tail is the difference between a loud pop and a theropod-ear-melting boom. Because of the behavior of dermal tissue upon damage, Ken Crpenter doesn't think sauropod tails could break the sound barrier (as presented in Eggs, Nests, and Baby Dinosaurs). However, in at least some diplodocids, there appears to be a row of "spiny things." I don't believe that any histological evidence was preserved, but my best guess is that they were keratin.
And to conclude briefly (hah!), if keratin was already present in sauropod caudal dermal evolution, then I see know particular barrier to evolving a softish continually growing tuft on the end of the tail. This is, of course, speculation, but at least there is no biological barrier to sauropods evolving a "popper," should the biomechanics end up consistent with a supersonic whip.

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