Re: Dinosaur tail dragging

["Jerry D. Harris" <102354.2222@compuserve.com>]

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Message text written by INTERNET:PTJN@aol.com

"
 A question for Jerry or for some engineers out there (Jim Cunningham?):
Would
it be energetically less expensive for an animal like a large sauropod to
hold
its tail off the ground or to drag it? "


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        Well, not having any engineering education, I'm not a good person
to ask about this!  ;-D  However, some problems have been solved by
nature's and evolution's engineering.  If there was, for example, a strong
ligament running along the tops of the tail vertebrae, and the ligament was
anchored, say, over the hips, then the tail would naturally tend towards
being held up, the same was a suspension bridge is held up by the support
cables above the bridge itself (this is, in fact, how sauropod necks are
suspended and held up).  Biological systems can be arranged such that the
_relaxed_ state is "held up" instead of dragged down.  A poor analogy (but
an analogy nonetheless) is the difference between the resting positions of
bivalve vs. brachiopod shells:  in bivalves, the resting state of the shell
is _open_; the animal has to exert energy to close the shell.  Brachiopod
shells, on the other hand, are, in resting, closed; they instead must exert
energy to _open_ the shell (this is why most brachiopod fossils are found
closed whereas most bivalve fossils are found either open or just on the
half shell).  The design of a tail isn't necessarily one where extra energy
must be exerted to keep it upright -- in fact, it may take more energy to
droop the tail than to keep it upright.

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                     Jerry D. Harris
                 Fossil Preparation Lab
          New Mexico Museum of Natural History
                   1801 Mountain Rd NW
               Albuquerque  NM  87104-1375
                 Phone:  (505) 899-2809
                  Fax:  (505) 841-2866
               102354.2222@compuserve.com