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Aves and Mononykus




I think Aves should remain as it is. The cladistic definition coincides with what most people (past and present) consider to be birds. We have to get use to the fact that characters like feathers and four-chambered hearts do not set birds apart, just as hair doesn't set the mammals apart. Where we draw the arbitrary lines have to be based on osteological characters for the most part.
Aves is and will remain a useful and stable taxon whether it is regarded as a separate Class, or a cladistically nested taxon (in my system, it is both). We could argue endlessly about the diversity criterion, but in this case other criteria, stability and tradition (both cladistic and eclectic) clearly demonstrate that Aves should be left anchored on Archaeopteryx (as much as I dislike such anchoring, in this case it seems justified).
I would like to move on to a discussion of whether Alvarezsaurians (incl. Mononykus) belongs in Aves (Chiappe's view) or not (Sereno's view). I am completely undecided, but I suspect Sereno is probably correct.
------Ken Kinman
********************************************************
From: "Jeffrey Martz" <jeffmartz@earthlink.net>
To: <Dinogeorge@aol.com>, <scott_hartman@hotmail.com>, <kinman@hotmail.com>, <dinosaur@usc.edu>
Subject: Re: Rock'n'roll !
Date: Thu, 10 Aug 2000 08:11:52 -0500


Dinogeorge wrote...
>Another way to define the class Aves is "all vertebrates closer to modern
>birds than to modern croocodylians," crocodylians being birds' extant
sister
>group. Then >all< the dinosaurs become basal birds.


Already taken by Ornithosuchia.

Eric Lurio wrote...
>A better thing to do would be to expand Aves to include some theropoda.

    Already does.
    And thats my contribution to taxonomic discussions for today.

LN Jeff
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