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The Birds (was "Rock 'n' Roll!")



On Thu, 10 Aug 2000, Scott Hartman wrote:

>      And all pterosaurs too (ornithodira is closer to birds than crocs)?  
> This doesn't actually bother me any, as it would more acurately reflect 
> evolution and morphological diversity, but is there a preexisting cladistic 
> definition for Aves that would have to be disregarded?  In not, someone 
> write that puppy up, although I don't know how ornithologists will react to 
> thinking of pterosaurs as basal birds...

There are two pre-existing cladistic definitions of Aves. The original one
was the crown group (equivalent to Neornithes). But this doesn't fit
traditional usage very well at all, so I think most people opt for "the
most recent common ancestor of _Archaeopteryx_ and modern birds
(Neornithes), plus all of its descendants".

Quite frankly, I think changing Aves *again* to be the equivalent of what
is now called Ornithosuchia is an *excellent* recipe for unnecessary
confusion.

If you really want to reflect the idea that a number of terrestrial
Ornithosuchia are secondarily flightless, why not use the strangely
neglected and highly appropriate name "Ornithes"?

You could even make an apomorphy-based definition for it: "the clade
stemming from the first species to possess wings synapomorphic with those
of Neornithes." Wouldn't be a very stable definition, at least from
current evidence, but it could serve for purposes of discussion. (Probably
would want to specify exactly what is meant by "wings", though.)

The current widest consensus would place it within Avialae, or at least
within Maniraptora, whereas Dinogeorge would probably stretch back a good
bit further.

_____________________________________________________________________________
T. Michael Keesey.........<tmk@dinosauricon.com>.........<keesey@bigfoot.com>
AIM <Ric Blayze>..............ICQ <77314901>...........Yahoo!M <Mighty Odinn>
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