[Taxacom] What taxon corresponds to "birds'?
John Grehan
calabar.john at gmail.com
Tue Nov 29 16:47:01 CST 2016
Ken,
I am intrigued by how a concept of alternating rapid and slow rates of
evolution generate a useful classifications. I would be interested in the
procedural steps connecting a theorized process of evolutionary to a
classificatory method (and examples of such practioners).
Also, in what way does 'cladification' become 'so complicated and
splintered' that it takes a lawyer or phylocoder to understand them. I have
seem innumerable molecular phylogenies generating many branching points
involving many taxa, but as long as the tree is presented I am not sure
what you see to be so complicated or splintered. With respect to splintered
are you saying some phylogenetic relationships should remain unresolved so
the pattern is 'simple'?
John Grehan (lawyer at large)
On Tue, Nov 29, 2016 at 5:31 PM, Kenneth Kinman <kinman at hotmail.com> wrote:
> Hi Stephen,
>
> I agree that the issues of rank and paraphyly are a continuing
> problem, except to those who just want to get rid of them (at the risk of
> throwing the baby out with the bath water). Nothing new there. Some say
> birds ARE dinosaurs, while others say birds are dinosaur descendants.
> Depends on how one defines dinosaur.
>
>
> As for the fossil record, it will always be incomplete, although
> the gaps tend to get smaller with new discoveries. But what is more
> important is that because long periods of stasis in that continuum are
> punctuated with bursts of accelerated evolutionary changes, those bursts
> can be used to classify (subdivide) the continuum into useful units.
> That's why I posted this morning about that 2014 article concerning the
> rapid burst of change around the base of clade Paraves and the importance
> of those changes. This makes those basal forms now more important than
> Archaeopteryx (which is no longer the appropriate taxon upon which to
> anchor the class of birds).
>
>
> Therefore, I cannot agree that where to draw the line is going to
> be arbitrary or unimportant. Punctuated equilibria make useful
> classifications possible, whereas cladifications become so complicated and
> splintered for some groups (such as dinosaurs and birds) that it eventually
> takes a lawyer or PhyloCoder to understand them.
>
> ---------------Ken
>
>
> ------------------------------
> *From:* Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
> *Sent:* Tuesday, November 29, 2016 3:07 PM
> *To:* Kenneth Kinman; John Grehan
> *Cc:* taxacom at mailman.nhm.ku.edu
>
> *Subject:* Re: [Taxacom] What taxon corresponds to "birds'?
>
> If we consider extant taxa only, then there is a large morphological gap
> between birds and (other) reptiles. On the other hand, if we had full
> access to the complete fossil record, that gap could completely disappear
> into a continuum. As long as all extant birds are included in a named taxon
> (of whatever rank), where to draw the line in terms of fossils is going to
> be arbitrary and unimportant. The main issue is rank. Should Aves be
> subordinate to Reptilia, or can we tolerate paraphyly? Some say yes, some
> say no. That is the problem!
>
> Stephen
>
> --------------------------------------------
> On Wed, 30/11/16, John Grehan <calabar.john at gmail.com> wrote:
>
> Subject: Re: [Taxacom] What taxon corresponds to "birds'?
> To: "Kenneth Kinman" <kinman at hotmail.com>
> Cc: "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
> Received: Wednesday, 30 November, 2016, 9:31 AM
>
> 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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