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Thoughts on Systematics and IntraSpecific Variations



All:

    This echoes back to some postings last week, but I've been thinking
about this after reading them...

    It seems to me, that the definition of characters to be used in a
cladistic analysis is the potentially source of disagreement in the results
of any given cladogram.   If there is no standard for characters that can be
agreed upon, then the results can be questioned.   (This has been one the
most confusing aspect of cladistics for me  -  who says what characters are
valid, and what does "slightly longer" mean in a femur? [If there are no
standards?]).

    It one thing to say that the squamosal is robust, it's another thing to
accurately quantify how robust that really is, versus other squamosals.  I
think we need to start looking at the work Ralph Chapman (and others, of
course) are doing in morphometrics.  It is possible that this work may
enable us to accurately describe a squamosal, or an orbital fenestra based
on a comparative range of sizes, robustness, or gracile-ness, or a
compendium of shapes (e.g. - REAL definitions of 'circular', 'oval',
'elongated oval', etc) - that paelontologists can agree on, and use as valid
characters in any analysis.

    This work could also help address the problem of valid ranges of sizes
and shapes for variations within species.  (The only work I know of that
started looking at similar problems was by Tim White, working with Don
Johanson with "Lucy" [ _Australopithecus afarensis_ ]).  I'm probably wrong
here, but I'd like to hear what other work was being in this area.

    Just my 2.5 cents,

        Allan Edels