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Re: Question about Archaeopteryx's (non) reversed hallux



David Marjanovic (david.marjanovic@gmx.at) wrote:

<No theropods except Scansoriopterygidae and Ornithothoraces have reversed 
halluces, in spite of earlier mistaken reconstructions. *Confuciusornis* has 
medially directed ones -- the intermediate condition.>

  Yeah, even *Confuciusornis* has a retroverted hallux. So this attribution
holds for pretty much all of Pygostylia.

  However, *Scansoriopteryx* lacks this twisted first metatarsal that was
implicated for the retroverted hallux. This is virtually untestable in
*Epidendrosaurus* despite the unguals facing in the same direction as all the
others on BOTH feet, since the preservation detail (negative moulds) and the
released photos do not actually allow the discerning of any other features of
the hallux or its metatarsal. For *Scansoriopteryx*, the isolated pes with the
coracoid lying alongside, the first metatarsal itself shows the condyles facing
90 degrees to the substrate of the slab, while the hallux itself is facing 90
degrees to that, parallel to the slab. The absence of a diagonal ridge crossing
from one side of the first metatarsal to the other, as was indicated as the
clue to having a twisted hallux, is further evidence for the absence of this
feature. This being the only pes available for the taxon, it makes the issue
relatively a refutal of there being a reversed hallux in the taxon.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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