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Re: Reversed Hallux in Theropods: a query



>in a lineage that _adapts_ to a ground-dwelling existence, no longer uses the
>big hallux for perching, and finds no other uses for it (such as grasping
>prey, as in eagles), the hallux fairly quickly becomes relatively smaller.
>Well, perhaps the best way to put this in the case of known theropods is that
>the rest of the foot _got bigger_, leaving the hallux behind.
>

I guess it depends on what you mean by "fairly quickly".  In birds, as I
said, the result is highly variable; terrestrial larks may have been around
for a good many millions of years with no sign of any such reduction; and
for an extreme example of an elongated hallux with a terrestrial (well, sort
of terrestrial) locomotor function consider the jacanas, which seem to be a
pretty ancient group - their long toes (including the hallux) allow them to
walk over lilypads (hence their alternate name "lilytrotter").  Also the
total loss of the hallux is actually a pretty uncommon condition in birds,
though it does show up in a few terrestrial groups.  And don't forget that
some ducks, which have a hallux totally lacking a grasping function, perch
extremely well in trees.

I'm not saying you are wrong - just that I worry about overly broad
generalizations.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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