Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."

["T. Michael Keesey" <mightyodinn@yahoo.com>]

--- Dora Smith <villandra@austin.rr.com> wrote:
> By what definition of Aves?   If Bird can be defined any way one wants and
> Microraptor, which was a member of another line of dinosaurs, qualifies as
> much as a bird as archaeopteryx does, then is "Aves" anything with feathers?
> If so, then any coelorusaurian dinosaur would qualify as a member of Aves.

_Aves_ and "birds" are not necessarily the same thing. Here are the definitions
(and I don't have my refs with me, so if anybody sees errors, please correct
them):

_Aves_ Linnaeus 1758 sensu Gauthier 1986 (made explicit in de Queiroz &
Gauthier 2002):
The most recent common ancestor of _Struthio camelus_ (ostrich), _Tetrao
[Tinamus] major_ (great tinamou), and _Vultur gryphus_ (Andean condor), plus
all of that ancestor's descendants.

_Aves_ sensu Chiappe 1992:
The most recent common ancestor of _Archaeopteryx_ and modern birds, plus all
of that ancestor's descendants.

_Neornithes_ Gadow 1893 sensu ???:
same as _Aves_ sensu Gauthier 1986 (But has this actually been phylogenetically
defined in some paper? I'm not sure.)

_Avialae_ Gauthier 1986:
The first ancestor of modern birds (_Aves_ sensu Gauthier 1986) which is not
also ancestral to _Deinonychus_, plus all of that ancestor's descendants.

_Avialae_ sensu Wagner and Gauthier 1999:
Same as _Aves_ sensu Chiappe

_Avialae_ sensu de Queiroz and Gauthier 2002:
The first ancestor of _Vultur gryphus_ to have powered flight homologous with
that in _V. gryphus_, plus all of that ancestor's descendants.

_Avifilopluma_ de Queiroz and Gauthier 2002:
The first ancestor of _Vultur gryphus_ to have feathers (hollow-based,
filamentous, epidermal appendages produced by follicles) homologous with those
in _V. gryphus_, plus all of that ancestor's descendants.

_Aviplumosa_ de Queiroz and Gauthier 2002:
The first ancestor of _Vultur gryphus_ to have "natal" down homologous with
that in _V. gryphus_, plus all of that ancestor's descendants.

_Avipinna_ de Queiroz and Gauthier 2002:
The first ancestor of _Vultur gryphus_ to have pennaceous feathers homologous
with those in _V. gryphus_, plus all of that ancestor's descendants.

_Aviremigia_ de Queiroz and Gauthier 2002:
The first ancestor of _Vultur gryphus_ to have remiges and rectrices homologous
with those in _V. gryphus_, plus all of that ancestor's descendants.

"bird":
An English vernacular term that has a pretty clear application insofar as
extant  animals are concerned (modern avians or avialans sensu anybody), but is
rather fuzzy when applied to extinct forms. Various authors more or less equate
"bird" with any of the clades mentioned above, although most commonly with
_Aves_ sensu Chiappe or _Avialae_ sensu Gauthier 1986.

To make sense of the above definitions, here is a cladogram showing the
specifier taxa and apomorphies in their most commonly accepted pattern (this
requires a monospaced font):

--+--(feathers sensu de Queiroz and Gauthier 2002)
  `--+--("natal" down)
     `--+--(pennaceous feathers)
        `--+--(remiges and rectrices)
           `--+--_Deinonychus_
              `--+?-(powered flight [possibly earlier or later?])
                 `--+--_Archaeopteryx_
                    `--"modern birds"
                       |--_Vultur gryphus_
                       `--+--_Struthio camelus_
                          `--_Tinamus major_

As I've said before on the list, I feel that the term "bird" should generally
be avoided in technical discussions. Use whichever of the above clades you
mean.

> What I am wondering is if birds really did come from just one narrow line of
> coelorusaurs.

You'd have to clarify what you mean by "bird".


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