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Re: Greg Paul is right (again); or "Archie's not a birdy"



> (Or at least clarify what they mean by "bird"?)

In prevailing neontological usage, it would probably be nowadays "Neornithes 
plus some extinct relatives, but not including Archie anymore". How far you go 
down the branch is open to debate (to most neonthologists it is not 
particularly interesting though). I am not sure whether there is any way to do 
this that is presently defensible, other than excluding even Enantiornithes:

Given that Ornithurae rests on a highly autapomorphic stem clade 
(Hesperornithes), the plesiomorphic part of which remains entirely unknown, and 
given the general lack of known basal diversity in Ornithuromorpha, the 
appropriateness of distinguishing between Ornithurae vs Ornithuromorpha vs 
Euornithes cannot at present be rigorously determined. In a similar vein, the 
supposed apomorphies of Pygostylia and Ornithothoraces (whose 
non-apomorphy-based definitions implicitly rest on the assumption that the 
supposed apomorphies *are* apomorphies) seem to be homoplasies at least for the 
largest part, or even - in case of the pygostyle - hint at nonmonophyly. 
Following the above argument, any or all of 
Ornithurae/Ornithuromorpha/Euornithes would be synonyms of Aves.

Of the definitions of Aves listed at 
http://www.taxonsearch.org/dev/taxon_edit.php?Action=View&tax_id=43, most are 
problematic because of the reliance on Archie and/or the likely nonmonophyletic 
"Ratitae". The rest (restricting Aves to Neornithes) is problematic because in 
neontological usage, Aves has rarely if ever been understood as a 
crown-restricted taxon.

And of course, Neornithes = crown birds is perhaps the only higher-level 
definition in this whole mess that is stable and widely accepted; even those 
who synonymize it with Aves do not argue about its content. On the contrary, a 
major argument for Aves = Neornithes seems to be the robustness of this clade.

I have come to agree with Sereno's point, however, that it is not a very good 
idea to synonymize the most stable higher-level taxon we have in this part of 
the tree with the one hat has been most contentious, still is, and likely will 
remain so for some time. 

Neornithes is good as it is; contesting its validity is unlikely to gain 
acceptance among neontologists. Hence, if we'd need a phylogenetic definition 
of Aves RIGHT NOW, the only one that pertains to a clade that is proven beyond 
all reasonable doubt, and to a clade interesting enough to warrant such a 
familiar name, and that is not wrought with a whole damn lot of controversy, 
would be:
"Anything closer to _Struthio camelus_ + _Vultur gryphus/Passer 
domesticus/Gallus gallus_ than to _Enantiornis leali_ + _Sapeornis 
chaoyangensis_ + _Confuciusornis sanctus_"
or equivalent. 

That clade would include only stem branches for which *non*survival at the K-Pg 
event would be quite parsimonious due to their being restricted taxonomically 
and/or biogeographically (it was a mass extinction after all) but it would NOT 
contain any stem group that was so successful that there is a real need to 
explain why they (i.e. Enantiornithes) are *not* around anymore today. This 
makes it attractive from an evolutionary standpoint too.

This solution might also be considered "not more bloody than necessary", 
because it takes a widely-known name and restricts its use to the one and only 
robust and major and significant clade within Avialae and including Neornithes 
according to present data, which is not very likely to be overturned by future 
data.


In a nutshell:
1. It is probably not a good idea to use Archie to define Aves
2. It is probably a good idea to retain Avialae
3. It is probably a good idea to retain Neornithes
4. It is probably not a good idea to use Aves for an insufficiently robust 
"clade" or insufficiently large/significant clade


(It would also stand an actual chance of settling the question "what is a 
bird?" in general knowledge, because it would at the present state of knowledge 
very nicely fit with "Paraves" and "Avialae" and "Neornithes" - we get "birdish 
dinosaurs" of which one part are "bird-winged dinosaurs" of which one part are 
"birds" of which the part that still exists today are "modern birds". As 
opposed to the present mess, you could teach this even to Junior High kids and 
they would understand it and learn nothing that is wrong now or likely to be 
wrong in the future.)


Regards,

Eike