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



On Wed, Aug 3, 2011 at 4:06 PM, evelyn sobielski <koreke77@yahoo.de> wrote:
>
>> (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".

Once you mention Archie it's not neontological usage any more.
Neontologists, I think, typically use "bird" to mean the extant
members, understanding that some extinct things are included but not
preoccupying themselves with what exactly those are (unless perhaps
they are very recently extinct).

> The rest (restricting Aves to Neornithes) is problematic because in 
> neontological usage, Aves has rarely if ever been understood as a 
> crown-restricted taxon.

Neontological usage isn't concerned with this issue at all. For
neontologists it is very obvious what is and isn't a bird (or an
avian).

> 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.

Great, *another* competing definition....

I think you're making the same mistake as was originally made. You're
trying to find some sort of "middle ground" solution that has some
kind of significance. But significance is reliant on historical
context. When Archaeopteryx was first inducted into Class Aves, it
seemed like a very significant grouping. Everything inside had
feathers, wings, stiffened tails, clavicles, etc. and everything
outside (e.g., Compsognathus) did not. But then each of those
characters were found to be more widely distributed (and, in the case
of feathers and clavicles, present in Compsognathus after all). People
found a variety of more or less Archaeopteryx-like forms that blurred
what had once been a sharp boundary.

Some day the same will be true of the clade you are delineating. We'll
find basal members that blur the distinction. (In fact, maybe we
already have--that's not the most stable area of the tree, is it?)

But the crown group will be significant for as long as both of its
branches persist. (And even should all palaeognaths die out somehow,
it will still be significant as the clade that survived the K/Pg
boundary and persisted into historical times.)

> 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.

The crown group is far more robust and far more significant.
-- 
T. Michael Keesey
http://tmkeesey.net/