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Re: 11th specimen of Archaeopteryx



Yes, sir, the cladogram in that paper does show the two as sister taxa, off on 
their own branch. There are other topologies, certainly, but I am talking about 
this most recent one.


On Nov 2, 2011, at 4:20 PM, Mike Keesey wrote:

> On Wed, Nov 2, 2011 at 9:58 AM, Jason Brougham <jaseb@amnh.org> wrote:
>> 
>> On Nov 2, 2011, at 1:49 AM, Scott Hartman wrote:
>>> 
>>> Likewise, if you map out paravian phylogeny and and where traits
>>> associated with arboreality show up, you'd see that there's simply
>>> nothing at all that shows up with Archie.
>> 
>> This statement is the most puzzling one I've read from you. Taking, as one 
>> example, the cladogram presented yesterday by Prieto-Marquez, Bolortsetseg, 
>> and Horner (A diminutive deinonychosaur (Dinosauria: Theropoda) from the 
>> Early Cretaceous of Öösh (Övörkhangai, Mongolia), we see that the closest 
>> relative of Archaeopteryx is Jeholornis, which was reported by Zhou and 
>> Zhang twice as having a  fully reversed hallux. The next more derived node 
>> is Sapeornis, which Glen and Bennett admitted may be an exception to the 
>> rule that basal birds foraged on the ground.
> 
> What do you mean by "closest"? A cladogram only portrays ancestry and
> descent, so the only measure of "closeness" in a cladogram is shared
> ancestry. And in that case you have it wrong: the closest relative of
> Archaeopteryx is *all* of Clade(Jeholornis + Aves), and the closest
> relative of Jeholornis is *all* of Clade(Sapeornis + Aves).
> 
> You may have been referring to a different type of "closeness", in
> which case Jeholornis could be the closest, but a cladogram wouldn't
> show that (unless its branches are somehow weighted). And, more
> importantly, this type of "closeness" would probably not be a good
> predictor of traits.
> 
> Instead, what does the bracketing tell us? It says that Archie is
> outside a clade (Clade(Jeholornis + Aves)) that has a reversed hallux,
> and the further outgroups lack a reversed hallux. So phylogenetic
> bracketing tells us nothing. The only thing we can do is look at the
> fossil itself.
> 
> (If the phylogeny of Prieto-Marquez & al. actually shows a clade that
> includes Archaeopteryx and Jeholornis but not Aves, then everything I
> said is wrong and please ignore it.)
> 
>> Archaeopteryx may have been less 'roosty' than its cousin Jeholornis, but 
>> this may most likely be a reversal
> 
> Based on what?
> 
>> and there was pretty clearly a long term trend toward acquiring arboreal 
>> features within the Avialae.
> 
> Sure, but Archie is near the very beginning of Eumaniraptora. It need
> not be a part of this trend.
> 
> Trends have to start somewhere but there is never any guarantee that
> it's at the very beginning of the branch.
> 
> -- 
> T. Michael Keesey
> http://tmkeesey.net/

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544