[Taxacom] What taxon corresponds to "birds'?
stephen_thorpe at yahoo.co.nz
Tue Nov 29 15:07:34 CST 2016
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!
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
have so abused
that taxon name with very different definitions" since
inclusiveness of a taxonomic category
has nothing to do with cladistics.
a basic principle of cladistics that relationships matter,
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.
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?
Mon, Nov 28, 2016 at 11:44 PM, Kenneth Kinman <kinman at hotmail.com>
> Hi All,
> For thousands of years (or
longer), there has long been a
classificatory distinction between reptiles and birds,
> Archaeopteryx eventually
showed that birds are clearly reptile
descendants. This was reflected in both informal and
> classifications as Classes
Reptilia and Aves. But the more recent
> discovery of fossil intermediates has
blurred where to draw the line
reptiles and birds. And around the same time we had
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
> definition of Class Aves has
become increasingly muddled, between those who
> would make it a crown group (and thus a
synonym of Neornithes) or
based on a group including Archaeopteryx, crown-group
> and all of their descendants.
> Given this muddled situation, I
have long favored expanding that
(for birds) to include avian dinosaurs that seem to have
> 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
> 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
Therefore, should we start calling it Class Paraves, or
> 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.
> Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu
> The Taxacom Archive back to 1992 may be
Intellectual Liquidity for 29 years.
Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu
The Taxacom Archive back to 1992 may be
searched at: http://taxacom.markmail.org
Liquidity for 29 years.
More information about the Taxacom