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Re: titanosaurs



George Olshevsky (Dinogeorge@aol.com) wrote:

<The whole notion of what constitutes a "character" is utterly subjective,
which is one reason I consider cladistics as no better than any other
method of doing taxonomy and phylogenetics.>

  Of course character selection is subjective, and so should cladistic be
a tool and not the end all, be all. Some serious cladists do not treat it
as the so-called "godsend" it is often made out to be my critics, but
there are those that attach special import to cladistic work above other
forms of analysis in conceiving of phylogeny, but so far, cladistics
removes subjectivity of weighting, and in this it offers better insight
than someone saying "this character is obviously better than that [for no
reason] and thus is worth _two_ of that character, and should mean that it
is better...." Eeek, but no. At that point science is out the window.

  Now, it wouldn't be too hard to perform a weighting experiment in PAUP*,
taking a small phylogeny of contentuous results, like Sereno's various
works, and simply duplicate all characters by 2; one then reduces to 1 all
characters that one thinks are not strongly weighted, and increase to 3
those that one thinks are more important. Figure out how you will treat
characters that are plesiomorphic, convergent, etc., either before you
perform the increase/decrease game or after. The extra characters will
enforce what you feel are "better" characters and give you an idea if it
has an effect on the tree. A good starting point would be Sereno's
Ornithischian tree, which involves many contentious results such as
hadrosaur, iguanodont, heterodontosaur, and hypsilophodont arrangements
with addition of new forms, and hope that you don't get something that
results in phyllogramatic garbage.

<Our best chance at doing something approaching accurate/real taxonomy is
to consider character suites (whatever they might be), biostratigraphy, 
biogeography, and anything else we can think of, and see how they stack up
against one another. That way we might be more able to catch the
inevitable errors that occur when these data are considered separately.>

  What, and ignore the data that involves how much of this data is crap
and recurs through time? What abpout reversals? Do they get a special
treatment, or are they similarly a unique evolutionary event that is every
bit as significant (and no more or less) than an apomorphic appearance?
Now think of this tangle:

  Look at all the taxa from the three continuous upper-Senonian, LK
Mongolian formations or the Judith River to Edmonton Groups. That they
come from similar habitats and formations and countries means that,
despite all data to the contrary on actual anatomy (controlled by genes
and not where you are) these taxa will be forced to share a similar
condition of inferrence, but its not even a synapomorphy, which refers to
anatomy by definition. Suddenly, a Nemegtian clade of troodontids is extra
special because they are of Nemegtian age, no matter the dissimilarity of
foot type and pertinence of one pes to another form (I'm referring to the
possibility of *Tochisaurus* being referable to *Saurornithoides*, rather
than forming a special clade with *Borogovia*, and that *S. mongoliensis*
in the Djadokhta means the Nemegtian species is "different" because of
this) that is controlled by something that genetically simply holds the
host of its evolution. Biogeography is a poor unit in cladistics or in
fact in any phylogenetic analysis, as dispersal events have nothing to do
with evolution except that at some point, separate groups of a single
species will diversify (but also, two overlapping populations of a form
may also diversify if to harvest particular crops, or even within the
sexes (as in the Hawai'ian O'ho, where females have a different curve than
the males and are ecologically distinct by feeding on exclusively
different flowers) and show that the distinction of biogeography does not
always hold true, and caution to its use.

  I won't even start on biostratigraphy, it has enough faults based on
absolute taxon distinctions based on species discrimination based on
subjective reasoning based on biostratigraphy based on ...

  Genetic developmental data in tooth formation in mammals as noted by Tim
Williams shows that a single event in a gene expression controls different
parts of the tooth. If we are to base our concept of an apomorphy as a
genetic marker based on evolution, and thus pertinent to phylogeny, then
we must note how that groups of features coming from a single mutation
occur as a single genetic apomorphy, and resultant morphological
apomorphy. Some studies show that biomechanical effects in limbs and
muscle elements to limbs alter given inter-related problems on posture,
locomotion, planti-, digiti-, or unguigrady, and styles of locomotion can
be linked, and are not found apart from each other; if they are, they may
become discrete, but even then this does not mean that a muscle coupled
with leaping and the osteological marker involved is not a unique single
event, versus a different muscle with the same osteological marker.

  Certainly I advocate all data at once, but cladistics works best where
data from evolutionary history is used. It was reported recently on the
list that in the latest issue of _the Auk_ a select group of extant
procellariiforms were analyzed, with two additional "characters"
delimiting biogeography, and it turned out that the results screwed the
matrix beyond any semblance of a cohesion of the morphological and genetic
studies reported therein. There is case history on this, after all, where
each datum has been involved in tests on its applicability to the
phylogeny of life on Earth, and frankly it seems that only genetic and
morphological with behavioral data is the only key. So far, and there are
good reasons including completeness of the record, to exclude eggshell
data and feather morphotype data from phylogenetic analysis, given that
these are not always well understood (as in details on filament morphology
and arrangment in *Sinosauropteryx*), corroborative (such as reports or
mention of preparating away of countour or downy plumage from
*Archaeopteryx* specimens). Such work can be done best as internal
analyses and a concerted effort to apply data to other analyses (called
"mapping") to see the pertinence of data and whether there is agreement or
not. Such arguments as how the dinosauroid and ornithoid eggshell
structures are mutually exclusive, etc., have never been tested and have
led to some rather hasty conjectures about some particular eggshell types
to excluding some taxa from sister group relationship when no concrete
study of the phylogeny of eggshells has occured yet.

  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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