[Taxacom] What taxon corresponds to "birds'?

[John Grehan]

One could well sympathize over the uncertainties of how inclusive to make a
particular taxonomic category, but it seems to me to be disingenuous to
assert that there is a problem of establishing a bird category because
"cladists
have so abused that taxon name with very different definitions" since the
inclusiveness of a taxonomic category has nothing to do with cladistics.
It's a basic principle of cladistics that relationships matter, not the
inclusiveness of a category (other than it being a monophyletic entity). It
matters not a cladistic hoot whether we decide to group birds into a class
Paraves or an expanded Aves, whether we include Archaeopteryx or not. Such
choices are inherent problems for any kind of taxonomy (as demonstrated by
Ken's own uncertainty as to what choice to make) - or am I mistaken?

John Grehan

On Mon, Nov 28, 2016 at 11:44 PM, Kenneth Kinman <kinman at hotmail.com> wrote:

> Hi All,
>        For thousands of years (or longer), there has long been a
> classificatory distinction between reptiles and birds, although
> Archaeopteryx eventually showed that birds are clearly reptile
> descendants.  This was reflected in both informal and formal
> classifications as Classes Reptilia and Aves.  But the more recent
> discovery of fossil intermediates has blurred where to draw the line
> between reptiles and birds.  And around the same time we had adherents of
> phylogenetic nomenclature  concluding that both paraphyly and ranked
> classifications are somehow "unnatural".  And yet decades later the
> PhyloCode is still extremely controversial and perhaps not likely to be
> implemented anytime soon (if ever).
>        In the meantime, even among strict cladists, the meaning or
> definition of Class Aves has become increasingly muddled, between those who
> would make it a crown group (and thus a synonym of Neornithes) or
> alternately based on a group including Archaeopteryx, crown-group birds,
> and all of their descendants.
>        Given this muddled situation, I have long favored expanding that
> Class (for birds) to include avian dinosaurs that seem to have preceded the
> common ancestor of Archaeopteryx and modern birds.  Given the importance of
> flight in the concept of "birds", I have come to the conclusion that
> asymmetical flight feathers are a primary evolutionary development in what
> constitutes a "bird".
>        Therefore, given the muddled debate whether Aves is the crown group
> or anchored instead on Archaeopteryx, I would perhaps suggest that we
> recognize a Class Paraves for "birds" rather than a Class Aves.  The
> discovery of Archaeopteryx long before all the other intermediates between
> reptiles and modern birds long made it a convenient anchor for a very long
> time, but it no longer seems to be so important given all the other forms
> since discovered (some older) with adaptations for flight (the asymmetic
> flight feather being a primary synamorphy, although even though its gradual
> developmental can be problematic given problems inherent in fossil
> specimens).
>        Therefore, should we start calling it Class Paraves, or expand
> Class Aves to become a synonym of Paraves.  I'm not sure which would be the
> best choice.  However, I am convinced that we need to expand the concept of
> "birds" as a Class separate from Class Reptilia.  Whether we call that
> Class Paraves or an expanded Class Aves is the question.
>                                   ----------------------Ken
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