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Re: Greg Paul is right (again); or "Archie's not a birdy"
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- Subject: Re: Greg Paul is right (again); or "Archie's not a birdy"
- From: Tim Williams <firstname.lastname@example.org>
- Date: Tue, 2 Aug 2011 10:07:34 +1000
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David Černý <email@example.com> wrote:
>> _Archaeopteryx_ had large wings, and (based on preserved position)
>> what appeared to be a reversed hallux.
No, not really. Not at all in fact. ;-)
It wasn't until the 21st century that the time-honored "reversed
hallux" of _Archaeopteryx_ was refuted by detailed anatomical work.
As you say:
> I mean, has there been anything new since Middleton's PhD
> thesis (2003, concluded that the hallux was directed anteromedially)
> and Mayr et al.'s paper that described the tenth specimen of
> _Archaeopteryx_ (2005, concluded that the hallux was "spread medially
> and not permanently reversed")?
Yup. Middleton's work demonstrated for the first time that it would
be anatomically challenging for a bird (or any theropod) to shift the
position of metatarsal I to the posterior surface of the metatarsus,
because the flexor tendons would get in the way. Perching birds get
around this by changing the shape of metatarsal I, giving the distal
portion of the shaft a twist or a kink so the attached hallux is
directed posteriorly. Taxa that lack any reorientation of the distal
articulation - such as _Archaeopteryx_, which has a straight,
symmetrical shaft - cannot have a reversed hallux.