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RE: Theropod posture-in-motion article



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> David Krentz
>
>
>   This is strange research.  What about very minute movements of the
> head, neck arms and trunk, not to mention some help from the tail that
> could help an allosaur with a turn. It would be interesting to see how
> much the trunk and tail could aid in a turn.  I cerntainly don't think
> that the rest of their anatomy was a stiff as a board, literally.

I'll have to wait for the paper in J Exp. Biol. to come out before dealing
with the details in public, but I do want to clear something up.  The main
point of the article is NOT to say that dinosaurs ran like humans with
boards strapped on them: it is instead to find an esimate of rotational
inertia.  Rotational inertia is something that cannot be prevented: the laws
of physics demand it, and this paper is a (very peculiar...) way to find
some values to model it.

However, although it cannot be stopped, rotational inertia CAN be
compensated for by numerous means.  The authors suggested a few: I buy a few
of them for paravians, maybe some others for tetanurines in general, but I
don't buy the postue for a subadult Allosaurus they propose.  Several other
funky morph (aka functional morphology) guys who've seen the paper have
suggested additional possible mechanisms or responses to deal with it, as
have posters on the list.

However, the fact remains: dinosaurs would have been forced to deal with
MUCH higher levels of rotational inertia than the vertical walking sticks
that are humans.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796