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Re: Panstems



Christopher Taylor (ck.taylor@auckland.ac.nz) wrote:

<Mike defines Panaves as the panstem clade of the node Struthio + Tetrao +
Vultur. Under the current popular phylogenies, this wouldn't really be a
problem - whichever the most basal branch of Aves is, most researchers
would currently hold it to include one of these three. But among other
taxa that have been suggested in the past to be the most divergent living
birds are Mesitornithidae, _Opisthocomus_ and _Todus_ (!). Conceivably, we
could get a situation where these are not Aves. By some older molecular
phylogenies, Passeriformes would not even be Aves by the definition given.
What to do?>

  I don't see a problem. Under either of the two current definitions of
Aves, one crown-based and the other a node-based clade including
*Archaeopteryx* + living birds, the topology of living birds remains a
part of Aves, and even a part of the crown clade, no matter how they are
arranged. By these two definitions, or even using Neornithes for the avian
crown clade (rendered a homodefinitional synonym of crown=Aves), all
living birds are members of the crown (Aves or Neornithes). The problem
with the bird topology above would posit that Passeriformes wouldn't be
part of the same node including galloanserans + other living neognaths,
would still be a member of Neognathae {*Vultur* <- *Struthio*}, but
apparently not of Neoaves {*Vultur* <- *Gallus*, *Anser*, *Struthio*}.

  On another note:

  I, personally, prefer *Passer* (sparrow) or *Corvus* (crow) as the
specifier, not *Vultur,* given that the two passerine birds are 1) more
common than *Vultur* (*Vultur* is largely isolated to one continent,
whereas *Passer* [and indeed, *Passer domesticus*] is of Laurasian
distribution, and *Corvus* [though not any particular species thereof] are
of nearly global distribution, save Antarctica), and 2) more prevalent in
collections or readily available to be made in collections for the purpose
of anatomical study, than *Vultur* would be, based on their shear numbers.

  Thus, in Article 11, a recommendation or rule (thereabouts in 11.8-11.9
or so) to advocate use of a living specifier could be made for the most
PREVALENT or AVAILABLE species for research purposes, prior to any
particular honorific. Another recommendation about finding the oldest
established name available to be included as a specifier, will allow
people to choose, as well. The use of *Vultur* as a specifier for birds
is, and I think only a few people will agree however, rather disparate
with the general impression of birds (largely composed of songbirds, not
vultures) most people will have.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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