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Re: Avian flight stroke origin



My apologies for being unclear. I did not mean that Archaeopteryx may have
stood in a tree like Penelope in that it would grip the tree with its
halluces. I meant that it would stand upright, without aid of hand claws.

However, on the point of halluces I still do believe that animals without
halluces, and galliform birds with poor perching ability, still do quite
well in trees and roost in them routinely.

In the wild turkey Meleagris, climbing in trees can be accomplished
without use of a gripping hallux. In the image below we see a wild turkey
climbing a narrow branch to reach fruit, and both halluces are free and
not gripping anything:

http://www.flickr.com/photos/jrnikon/3240582435/sizes/l/in/photostream/

And here we see that Meleagris' hallux is elevated, which is to say
proximal to the other toes. This must limit opposability:

http://4.bp.blogspot.com/_nkdggYHwcLc/TVHpAS7YKGI/AAAAAAAAEBc/ap8oiypVla8/s1600/WildTurkeyFEET_2126.jpg

Goats, as we know, also climb trees without benefit of a hallux:

http://www.odditycentral.com/videos/the-tree-goats-of-morocco.html

> Jason Brougham <jaseb@amnh.org> wrote:
>
>> That may be, but Greg Paul never actually depicted Archaeopteryx
>> climbing
>> like a Hoatzin, did he? When he depicts Archaeopteryx in a tree, like in
>> Figure 9-3, page 212, of Predatory dinosaurs of the World, he shows it
>> standing on a  limb like a Chachalaca, and I think this is a
>> conservative
>> depiction that stands up to everything we've learned about Archaeopteryx
>> since.
>
>
> I disagree.  Chachalacas have a perching pes.  Do a Google Images
> search for 'Chachalaca' and you'll get photos galore that show a
> chachalaca in a tree with its large, incumbent hallux wrapped around a
> tree limb, in opposition to the front toes.
>
>
> http://www.naturephoto-cz.com/grey-headed-chachalaca:ortalis-cinereiceps-photo-8051.html
>
> http://www.fredmiranda.com/forum/topic/787667
>
> etc etc
>
>
> Here's one thing that we've learned about _Archaeopteryx_: it couldn't
> perch.  The hallux was relatively short, positioned relatively high on
> the metatarsus compared to modern avians, and not at all reversed.  So
> putting _Archaeopteryx_ out on a limb chachalaca-style is... well,
> going out on a limb.  IMHO, it's not a "conservative depiction" at all
> to claim that a theropod with a non-reversed hallux could perch like a
> modern bird (in this case, a cracid).
>
>
> Granted, paravians do tend to show some changes to the hallux compared
> to the primitive theropod condition, including in the more distal
> location of metatarsal I  - this was discussed by Xu and Zhang (2005)
> as part of their description of _Pedopenna_.  But this more distal
> hallux (also seen in microraptorines and velociraptorines) is a far
> cry from what we see in modern birds, and even in many Cretaceous
> non-euornithean birds (including sapeornithids/omnivoropterygids and
> enantiornitheans) that have a ped adapted for opposable grasping
>
>
>
>
>
>
>
> Cheers
>
> Tim
>


Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
81st Street at Central Park West
212 496 3544
jaseb@amnh.org