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Re: Blood flow in Sauropods



At 12:05 AM 9/14/95, Derek Tearne wrote:
>The reason which I have heard cited is that mammals are restricted to
>7 vertebra in the neck and no mammal has more (although I knew a
>woman once who had eight... ).
>
>This pretty much restricts the length and flexibility of mammalian necks.
>
>Birds, reptiles and dinoraus are not restricted in this way and
>can therefore evolve much longer necks.

        I can't say i've heard this before -- just precisely what does
"restricted" mean?  Is this supposed to mean that it's physically
impossible for mammals to evolve more (or less) than seven cervicals?  How
would one determine such a limit?  After all, most of the long-necked
sauropods have similar numbers of cervical vertebrae, except for
_Mamenchisaurus_ (I'm not sure about other euhelopodids) which went and
increased it from 12ish to 19.  Under the proper selective potentials, I'd
think that a mammal could and would do something similar.



Jerry D. Harris
Shuler Museum of Paleontology
Southern Methodist University
Box 750395
Dallas  TX  75275-0395
(214) 768-2750
FAX:  (214) 768-2701
jdharris@lust.isem.smu.edu
        (Compuserve:  73132,3372)

---------/O\------*     --->|:|:|>     w___/^^^\--o

"If it looks like a duck, walks like a duck, and
quacks like a duck, then it is the sister taxon to,
but cannot parsimoniously be, the direct ancestor
to all other ducks."

                                --  _not_ W. Hennig

---------/O\------*     --->|:|:|>     w___/^^^\--o