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Re: titanosaurs



George Olshevsky (Dinogeorge@aol.com) wrote:

<No, cladisitics doesn't remove the subjectivity of weighting, it simply 
imposes the "null" or "equal" weighting on all characters, which is just
as subjective as any other weighting system. Just as there is no good
reason to weight one character twice as much as another, there is also no
good reason to weight them all equally. This is one of those philosophical
problems that I have with morphological cladistics. At least in molecular
cladistics an equal weighting scheme is reasonable, since the four bases
of DNA have a practically even chance of being at any particular locus. In
morphological cladistics there is no reasonable way to weight characters,
so every such analysis becomes suspect.>

  Actuall, if something has a null value relative to another, it carries
no phylogenetic weight, and is therefore, weightless. It removes weight.
Weight occurs when a character is considered more important than another,
but since this is relative to the person, and no data has supported any
character used to weight a taxon in any direction based on what was
supported in a phylogeny regarding the numerous 1997-2002 sauropod
analyses conducted. Instead, each analysis depended on the characters
included and excluded _only_. A matrix including _all_ features used by
Barrett, Upchurch, Wilson, Smith et al., Curry-Rogers and Forster has not
been done but would be a good idea given the neccessity of increasing the
matrix to the level seen in recent theropod matrix frameworks. As for
molecular work, there are actual combinations that cannot occur between
any two given molecules, that limit the variability in which they may
combine, but as it can be noted, selectively making one combination of two
possibily combos as being better than the other is simply unscientific and
... hey, I can't find the work because it's just too heinous an idea to
consider choosing to ignore a possibility because one things something
else is better. This has nothing to do with George, I have seen another do
it, and am getting emotional right now because of arguing selectivity on
no grounds referring to the features being selected for or against.

  For instance, what exactly makes bifidy in the cervicodorsal series
special? If I were to have three characters reflecting a close affinity to
one taxon, and one to another, what makes a single character more special?
Incidentally, talking about a euhelopodid origin for *Opisthocoelicaudia*,
*Euhelopus* has monofid neural spines, and the monophyly of a Euhelopodid
has been seriously questioned and only a Mamenchisauridae seems to be as
seriously considered by sauropod specialists today, given work reflecting
a basal titanosauriform position for *Euhelopus* found by Wilson and
Sereno (1998).

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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