Bird classification & macroevol'n

[Colin McHenry <s172579@student.uq.edu.au>]

At 23:57 8/01/96 -0500, you wrote:

>I did notice that it is very different from most classifications, but 
>intuitively many aspects of it make sense to me.  It is also much more 
>compact than the traditional "Class Aves", without the thirty or so 
>orders usually included therein.  This seems to me more in keeping with 
>the fact that modern bird groups have only had about one hundred million 
>years (at MOST) to differentiate.
>
>     Thanks!
>
>     Nick Pharris
>     Pacific Lutheran University
>     Tacoma, WA
>

Sorry to pick you up on a technicality, but if you are labouring under the
impression that degree of differentiation is proportional to time since
divergence, then you are probably going to confuse yourself (with the
possible except of selectively neutral DNA sequences).  Morphological
differ'n more often follows patterns of radiation - and birds underwent a
very large radiation into a set of niches very different from that that held
by their non-avaian ancestors.  You will also find that most of that
differentiation appeared very early on in their history, as well - they have
been pretty conservative since they filled up all that empty niche space
after the initial radiation.  This pattern of macroevolution appears time
and time again (think of the Triassic radiation of the dinosaurs and the
Paleocene radiation of the mammmals), and may be one of the major causes of
the Punctuated Equilibira pattern...(if only Eldredge & Gould had used an
ecological model of evolution in 1970 instead od a bogus genetic one we'ed
all have been saved a lot of fuss.....)  :-)

On a seperate note, have any of the therapod fetishists out there got any
general rules of thumb for deducing feeding ecology from gross jaw and tooth
shape (at a level that might be applicable to other taxonomic groups)?


Colin

P.S. A public thanks to the most useful person in N. America for answering
yesterday's query on Megalneusaurus....Tracy Ford, come on down....