RE: Brachiosaur Defense

[Toby White <mwhite@houston.rr.com>]

We've touched on the difficulties of turning in large theropods before. 
 Wouldn't arctometatarsaly reduce that problem?  Say Timmy the Tyrannosaur 
is trotting after Turok.  Turok turns and tacks left.  Timmy turns his 
torso to track Turok.  Timmy's tarsus may not turn in time. But, instead of 
tripping, mtIII transforms the torque into tension against mtIV (enough of 
that) which rebounds by kicking the pes out at an angle, stabilizing 
Timmy's turn.

  --Toby White

Vertebrate Notes at
http://dinodata.net and
http://home.houston.rr.com/vnotes/index.htm


On Monday, January 31, 2000 10:30 AM, Thomas R. Holtz, Jr. 
[SMTP:tholtz@geol.umd.edu] wrote:
>
> Previous interpretations of the arctometatarsus as a kind of energy 
storage
> and release device (either by fore-and-aft rotation or as a pistoning
> motion) have been proposed... er, previously.  I suggest that these might 
be
> in operation in some of the forms, but as the amount of motion is 
limited,
> the amount of energy stored would not be too considerable.  Furthermore,
> some of these motions would be prohibited in certain forms (i.e.,
> fore-and-aft rotation in tyrannosaurids, where the crescent-shape of the
> proximal mtIII would lock that bone and keep it from rotating).  I offer 
the
> further possibility of a method of redistributing the forces from mtIII 
to
> mtII and IV.  Further analyses await to test this...
>
> In any case, if the energy storage system was in affect it would not 
allow
> theropods with arctometatarsi to jump about like kung fu fighters.  The
> analogy would be to the snap-ligaments in, for example, horses: it is a 
way
> of changing kinetic energy to potential when the foot touches down and 
the
> ligaments stretch; when the foot kicks off again the energy is released
> giving an extra boost (and thereby reducing the cost of locomotion for 
that
> step).

>               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): 301-314-7843