Re: The nearbird

[Tim Williams <tijawi@yahoo.com>]

David Marjanovic wrote:

> The first
> toe is preserved lying medial to metatarsal II. 


As Xu et al. put it, "As preserved, pedal digit I lies medial to metatarsal II, 
suggesting a non-reversed hallux."  It does seem unlikely that _Anchiornis_ had 
a perching pes.  However, alone the preserved position of the hallux doesn't 
impact a great deal on whether the hallux (first toe) was reversed or not.  As 
pointed out by Middleton (2001), it's the morphology of metatarsal I that 
counts (plus the articulation on the rest of the foot).  


This was recently reinforced by Hutchinson & Allen in their Naturwissenshaften 
paper: "A caudal position of the fossa for metatarsal I and a longitudinal 
twisting of the metatarsal I shaft are the two best indices of hallucal 
retroversion â  preserved position is not reliable as it is too subject to 
taphonomic distortion."  



Refs:

Middleton KM (2001). The morphological basis of hallucal orientation
in extant birds. J. Morphol. 250: 51â60.

Hutchinson JR and Allen V (2008).  The evolutionary continuum of limb function 
from early theropods to birds.  Naturwissenshaften DOI 10.1007/s00114-008-0488-3




Cheers

Tim