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Re: BIRD CHARACTERISITICS



    

      I was just sifting through some old email and I stumbled onto this 
one from an old thread ( one of the most interesting) and I realized 
that I had not answered it. So in the spirit of Christmas I want to 
resurrect an old scientific debate.



> 26 Oct 1997 12:42:49 CDT

>From: "Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>

>Subject: Re: BIRD CHARACTERISITICS

>
>Matthew Troutman wrote:
>> Do you mean when you talk about the tarsometarsus the one seen in 
>>ornithuraes? The kind of metatarsus seen in Archaeopteryx and is the 
>>same one as the one in enantiornthines.

>        Here's a question for the bird workers out there. Hou, Martin, 
>Zhou
>and Feduccia make a big deal about similarities (that sound like
>symplesiomorphies) between the metatarsus of _Archaeopteryx_ and
>Enantiornithes. Now, let's ignore for a second that they managed to 
code
>their characters in such a way that this conformation was treated as >a
>seperate evolutionary novelty unrelated to the neornithine 
>tarsometatarsus.
>Let's also ignore polarity for the time being:
>
>        Is the metatarsus of _Archaeopteryx_ more similar to that of 
the
>Enantiornithes? Wellnhoffer (_Illustrated Encyclopedia of Pterosaurs_) 
says
>that archie's metatarsus was unfused, has this been refuted? Is there
>something I'm not seeing here?

     Fedducia and Martin both claim that the Maxberg specimen ( sadly it 
was stolen a few years ago) had its metatarsals fused in a 
proximo-distal pattern like enantiornithines ( or their "Sauriurae" ) 
and in contrast to the disto-proximal pattern seen in Ornithurae birds. 
I do not know that this claim can be proven.
 
>        Now, add polarity back in. If archie's metatarsus is more 
silimlar
>to that of the Enantiornithes, how does it compare to that of a 
suitable
>outgroup (e.g. Troodontidae, Dromaeosauridae, etc.). Bear in mind that 
Hou
>et al.'s outgroup choice (_Petrolacosaurus_) is undoubtedly unsuitable 
for a
>proper phylogenetic analysis.
>
      Honestly I cannot make an imformed opinion on this subject other 
than the metatarsus of dromaeosaurids is quite similiar to than of 
Archaeopteryx and that I think Tom said somewhere that the metatarsus of 
Hulsanpes is fused. What pattern; proximal- distal or disto-proximal, is 
not stated. ( Have any insights Tom?) 
     Hou et al's paper for the most part was good and interesting. But 
their views on the ancestry of birds clouds their thinking on many 
issues ( Sauriurae, for example.) The speculation that Archaeopteryx is 
somewhat off the main line of avian evolution is interesting and may be 
the most parsimonous if the Ornithothoraces is artificial ( I for 
example, believe that the strut-like coracoid, pygostyle etc. may have 
evolved in parallel, which is a distinct possibility.) Hou et al also 
state that the ossification of the bony sternum, carina, and triosseal 
canal probably evolved in parallel. The sternum of Eoalulavis supports 
that early birds ( "sickle-claw", Archaeopteryx) had a widely unossified 
sternum and that the carina may have arisen early in enantiornithine 
evolution and possibly in parallel to that of ornithurae birds. The 
triosseal canal of ornithurae birds is formed mainly by the coracoid and 
incipently by the scapula and furcula. The triosseal canal of 
enantiornithine birds is formed mainly by the scapula and incipently by 
the coracoid and furcula. 
     I am not supporting Feduccia or Martin totally but I do believe 
they make some vald points that are all together dismissed and ignored. 
 
     While we are on the subject , Iberomesornis, what is it? 
Enatiornithine, ornithothoracine, something else? More study must be 
done, particulary on the triosseal canal to tell conclusively what it 
is. 

     Now again, I am not completely supporting Feduccia or Martin, the 
points made by Chiappe and Sanz are probably more parsimonous, but I 
have some reservations. The features Feduccia and Martin and Hou and 
Zhou site for Sauriurae: anterodorsal ishchial crest, dorsal knob on the 
femur, proximo-distal fusion of the metatarsus can be plesiomorphic for 
Aves, and they probably are.
 
 So if anybody has any thoughts feel free to reply.


Merry Christmas,

 WMattTroutman 

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