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Re: BIRD CHARACTERISITICS







 

>>>        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.).
>
>Neither troodontids nor dromaeosaurids as currently know have fused
>metatarsi.  Basally, birds seem to fuse from the top down and reverse 
it
>further up the tree.

     This is where I find the  Chiappe phylogeny ( the one that is the 
most accepted among paleontologists) unlikely. Assuming that 
Archaeopteryx is the most basal avain, the proximo-distal pattern of 
fusion is primitive for Aves, but then it seems to be lost, as in the 
supposed transitional form between the enantiornithes and Ornithurae, 
Iberomesornis, and regained (enantiornithes) and reversed (Ornithurae.) 
This, to me, seems unlikely and this is just one of the many 
reservations I have about the current accepted phylogeny of basal  Aves.

>>      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.
>
>But I never said that Hulsanpes was a dromaeosaurid... :-)

 I was just assuming that Hulsanpes was either dromaeosaurid or near 
dromaeosaurid.

>>What pattern; proximal- distal or disto-proximal, is 
>>not stated. ( Have any insights Tom?) 
>
>The top is fused, the bottom unfused, if memory serves.
>
>>     While we are on the subject , Iberomesornis, what is it? 
>>Enatiornithine, ornithothoracine, something else?
>
>Basal ornithothoracine, according to Chiappe and Sanz.

     In the few emails that I got regarding this issue everybody assumes 
that Iberomesornis is a transitional form. The characters that bind the 
Ornithothoraces together are rather trivial ( ventral processes on 
cervico-dorsal vertebrae) or likely to evolve in parallel due to flight         
( strut-like coracoid, pygostyle.) 
      I have more reservations but will save them for a later time.

 Merry Christmas,
Thanks in Advance, 

 WMattTroutman


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