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Re: In (premature) defense of the USNM



----- Original Message -----
From: "Michael Skrepnick" <palaeopaint@dinosaursinart.com>
Sent: Sunday, May 05, 2002 5:25 AM

HP Philidor11 wrote:

> > Consider the following two assertions:
> > Any animal observed to have feathery integument should be drawn with
> > feathery integument; any animal not observed to have feathery integument
> > should be drawn without feathery integument.
> > and
> > I have a logical argument which has not been refuted that a certain
number
> > of animals I select had feathery integument.
> > Which is more scientific?  I'm arguing that neither should be dismissed
> > out of hand as unscientific.  In fact, if forced, I'd say that entire
reliance
> > on observation was more scientific, but I'd hope never to be forced.

I do say that the first is less scientific if the "logical argument" itself
is scientific. Consider the following 4 assertions:
- Any animal observed to have feathery integument should be drawn with
feathery integument;
- any animal _observed not to have_ feathery integument, but something else
(naked skin, scales, hairs), should be drawn without feathery integument;
- any animal _not observed to have_ integument (none being preserved)
requires a "logical argument", such as phylogenetic bracketing.
- If phylogenetic bracketing fails ( = is ambiguous, or if competing
phylogenetic hypotheses produce different solutions), less secure methods
(could it have required insulation, display...?) should be considered, but
basically the artist is free then.

A good introduction into phylogenetic bracketing can be found at
www.dinosauria.com/jdp/misc/parsimony.htm (scroll down to Parsimony and
Anatomy, and remember it's from 1997, when the only definitely non-avian
feathered dinosaur known to most scientists was *Sinosauropteryx*).