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Re: decoupling

Darren Naish wrote:

> Decoupling is the correct term with reference to the caudofemoral
> musculature in birds versus that in non-bird theropods, yes (see
> Gatesy's stuff), but not with reference to association between the
> wings and hindlimbs.


Something must be "coupled" before it can be "decoupled".  Like any other
relative statement (larger, faster, derived, etc.), decoupled is most
meaningful if you reference it to something in a lineage's history that is
more coupled.  Keep in mind that there's no need to decouple everything at
once; parts can become less linked (functionally and/or anatomically) at
different levels of the heirarchy.  Ken Dial and I have proposed that the
fore and hind limbs of archosaurs became functionally decoupled with the
origin of bipedalism.  Having decoupled fore and hind limbs was likely the
primitive condition for theropods.  Birds are thus decoupled relative to
quadrupedal archosaurs, but not relative to other theropods.  The
decoupling we think is important for the origin of flight is the tail and
hind limb in some coelurosaurs relative to basal theropods.

Steve Gatesy

Stephen M. Gatesy
Dept. of Ecology & Evolutionary Biology
Box G-B209
Brown University
Providence, RI 02912
401-863-7544 (fax)