RE: true semilunates & carpometacarpi (was Caenagnathiformes)

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Ken Kinman wrote:

>      Anyway, inserting the word "usually" into the wording of my
>preferred definition of "true" semilunate, we get:
>A distal carpal structure which (1) is enlarged so as to fully cap
>metacarpals I and II; (2) usually has a distinctive semilunate shape;
>and (3) has a pronounced trochlear groove on the proximal side.


So what if a theropod has (1) and (2), but not (3).  Is it a bird, or not a
bird?  Either way, the "precision" is already lost.


"Phlidor" wrote:

>Modifying your statement to assist in making my point: 
> <The fossil record tells us that the divisions between one Cla[de] 
> and the next disappear as you go back in time.  This undermines the 
> very concept of a "Cla[de]".> 

You haven't "modified" what I said; you've perverted it.  The divisions do
not "disappear"; only one character needs to be used to distinguish sister
clades.  Under the "Class" system, one clade in a sister-pairing may be
promoted to the rank of "Class".  I think *that* is very silly.

>Classes are certainly more useful because they do not relay on 
>retrograde analyses, but on immediate observation of clear differences.
>They are unquestionable and essential, no doubt about it. 

Bulldust!  Even today, people still quibble over how many "Classes" the
fishes (Linnaeus' Pisces) should be divided into - even discounting the
extinct groups.  As for the Arthropoda...  that's a whole other story - is
Crustacea a Class or Phylum; is Collembola an Order or Class?, etc etc etc.

Your "immediate observation of clear differences" are entirely in the eyes
of the beholder.  What is a "clear difference"?  Can it be quantified?  Do
100 "clear differences" = 1 Class?  I'd advise re-reading Tom Holtz's
message on "Taxonomy's dirty little secret."

>We know that the distinctions between birds, for instance, and 
>some representatives of another large group called dinosaurs 
>would disappear as we went back in time.  Therefore, we won't 
>look back in time in identifying groups.  Any classifications 
>based on the beginnings of distinctions could result only in 
>creating problems for ourselves.  So we'll avoid that in setting 
>Classes. 

Yes, looking at the fossil record is a complete waste of time.  It's only
the most direct and empirical way of tracking organismal change over time.
In fact, let's just give up trying to understand evolution at all; it's all
just TOO HARD.  Let's just package animals on the basis of whether they have
feathers or fur or scales, and whether they crawl or fly or run.  All the
rest requires too much thinking.

>And if some people want to be stuck in their labs all day feeling 
>around bony knobs like phrenological pathologists to determine 
>which small subsubsubgroup an extinct animal belongs in, okay, 
>but I'd rather be out with the traveler on horseback, tromping 
>worms. 

Or worse!  There are these little creatures called "bacteria" and "protists"
that are smaller than worms, and require even more delicate and esoteric
"feeling around" to discover their identity.  Think of all those people with
pipettes and thermocyclers trying to discover the genes and molecules
responsible for causing disease when these little creatures enter a human
body.  Get these folks out of the lab, and out on horseback where they can
do some *real* science!

On a serious note: This kind of response from "Philidor" is the reason why
Science gets such a bad rap.  People who dedicate their lives to untangling
the mysteries of Life in its multidinous forms - whether it be human beings
or broccoli or anthrax or bones with "little bony knobs" - have a vocation
as worthy as any other.  "Philidor"'s attitude stinks, and I rather expected
better.



Tim