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Re: Reversed Hallux in Theropods: a query



In a message dated 95-11-24 20:42:00 EST, ornstn@inforamp.net (Ronald
Orenstein) writes:

>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.

Umm--flying birds are hardly obligatorily ground-dwelling, cursorial bipeds.
They are not obliged to place their feet on the ground and walk for most of
their lives. And the retroverted hallux is not _necessary_ for perching, of
course, merely a quite convenient adaptation for it that arose in the lineage
that led to birds. The problem is to account for the presence of the
retroverted hallux in so many different theropod lineages, not to figure out
all the different things all the different birds of the world can do with
their feet.