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Do 3 middle-ear bones really = 1 mammal? (was RE: SCIENCE AND CLA SSIFICATION)



Ken Kinman wrote:

>But we now have sufficient data to define Aves in a more scientifically
>rigorous fashion (osteologically), just as was done with Mammalia >decades
ago.

and this howler...

>The new definition of Aves, if done correctly, will do for birds
>what has so long been successfully done with mammals. 

"Decades ago" the Mammalia was thought to be polyphyletic; Simpson himself
carried the banner for this cause.

>The 
>presence of hair and lactation roughly corresponds to the scientific 
>definition, so there have been no big problems reconciling the two 

Ah yes, the "three-ossicles" thing.  Check out Cifelli's paper in JPal - it
might set you straight on how "easy" you believe it is to define a "mammal"
anatomically.  Short version: It ain't easy, and mammal paleontologists
don't pretend that it is.


David Marjanovic wrote: 

>Nope. Nopcsa explicitely starts with a bipedal Proavis, and AFAIK with 
a 
>theropod. 

I thought so. 

> BTW, going to any of Vienna's university libraries -- for example -- 
> does hardly give one the exercise of walking, unless you are content 
> with 5 minutes, 

You live in Vienna?  Cry me a river, David.  You live in one of the most
beautiful cities in the world - take a scenic route to the library.  ;-)

>and I wouldn't call the usual street air outside of the 
> subway and bus/tramway "fresh air", neither the one in the libraries 
> themselves. 

Ah, life in the urban jungle... 



Tim

------------------------------------------------------------ 

Timothy J. Williams 

USDA/ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163 




      The new definition of Aves, if done correctly, will do for birds
what 
has so long been successfully done with mammals. The scientific
definition 
will be precise (osteological), but it will roughly coincide with the 
presence of "vaned" feathers.  All those more primitive "protofeathers"
on 
Sinosauropteryx, the newly-discovered pterosaur, and even that 
bristly-tailed psittacosaur, are apparently just that (PROTOfeather 
homologs).  Whether the structures of Beipiaosaurus are best regarded as

advanced protofeathers or primitive vaned feathers remains to be seen.
In 
any case, a precise osteological definition should take precedence over 
feathers, eggshells, origins of flight, and other characters that
fossilize 
poorly (and that obviously includes bird excrement as well).  :-)
     Within this new context, the evolution of brooding and powered
flight, 
the ornithoid eggshell evidence, and so on, will begin to make more
sense, 
and it will also clarify many of the debates that have paleontologists
and 
ornithologists insulting each other in the press and in other public
forums 
(fora?).  The whole Longisquama debate is one of the more embarrassing 
examples.
      I am proposing a long-thought-out, moderate paradigm shift that I 
believe will enhance stability.  Both scientists and the public alike
will 
have to learn that the old "bird = feather possession" idea is
inaccurate 
and out-of-date.  But shifting to the possession of "vaned" feathers
seems 
the best way to accomplish a smooth transition (especially with the
public). 
  What we now have is confusion and taxonomic instability.  The question
in 
my mind is not *whether* we should draw a new line, but *where* it
should be 
drawn.  To continue drawing the line at Archaeopteryx (eclectically or 
cladistically) is a tradition that I think we must abandon for
everyone's 
sake.
      More generally, we are faced with a decision between: (1) an
eclectic 
emphasis on apomorphy (character)-based taxa or (2) a purely cladistic 
emphasis on node- and stem-based taxa.  The latter seems to sacrifice 
stability of content in favor of stability of definition (definitions
which 
cladists are already fighting over, requiring a new bureaucratic code to

settle them, and no sign that its decisions will be widely followed
anyway).
       If you look at it from a broad perspective, all classifications
are 
arbitrary and "typological" to some degree, and pure cladism is just 
promoting a new form of arbitrary "typology".  Benton (2000) has already

pointed out that in the end, we will be no better off, and thatin many
ways 
we will be much worse off if we follow this path.  The pendulum has
swung 
too far already (swinging so far, that even I have been ousted from the 
"Cladists Club", which is very odd because some eclecticists think I'm
too 
much of a "cladist").
      Anyway, I certainly look forward to Mickey Mortimer's upcoming 
analysis.  And I will seriously consider it's outcome as I continue 
searching for a precise osteological definition of Aves that can be made

more precise in the future (as has been done with the Mammalia
definition).
         ------  Cheers, Ken Kinman



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