[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: giant birds



At 12:08 PM 11/12/99 +1300, Kendall Clements wrote:
>
>I still cannot see how BCF can be compatible with the published 
>topology. If it was non-avian theropods would nest within aves,

You misunderstand what George means in saying that dinosaurs are birds.
What he is saying is that the synapomorphies uniting Dinosauria are
adaptations related to flight, or at least to arborealism.  Therefore, he
chooses to expand the term "bird" to include all dinosaurs.  He is in no
way suggesting that Neornithes, or even Avialae, is more inclusive than
Dinosauria.

>other way around. Saying "they're all birds" does not explain the 
>problems BCF produces with character polarity at the base of the 
>theropod tree. Analyses pretty consistently place avians as the 
>sister-group to deinonychosaurs,

Which is not in conflict with BCF.  The clade called Aves (or Avialae, or
whatever), is NOT the same as what George calls birds.  His definition of
"bird" would be more or less the same as that of Dinosauria.

>me to address these issues, so let's hear from someone else. Is BCF 
>compatible with the conventional phylogeny?

In the sense that George means, yes, it is.  Avialae is still the sister
group of Dromaeosauridae.  What George is saying is that the common
ancestor of at least Neotheropoda was already a powered flyer, and the
common ancestor of Dinosauria was at least arboreal.

In other words, all he is doing is moving the position of the feature
"powered flight" on the traditional tree from a point slightly basal to
_Archaeopteryx_ to a point deep inside the dinosaur clade.

--------------
May the peace of God be with you.         sarima@ix.netcom.com