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Convergence and Character States



Message text written by INTERNET:znc14@TTACS.TTU.EDU
>The character is "skull", the character state is "does not exhibit
streptostylic kinesis = 0," and "exhibits streptostylic kinesis = 1."<

        This may be fine as far as this goes, but I would hope that anyone
looking more closely at nuances of anatomy ought to see that this
bipolarity of data classification is unsatisfactory.  As Tom and Chris have
both said at various times on the list, the simple division of character
states into two types, when with a little more investigation, many are
possible, makes for overly-simplistic analyses.  To take another example:

Character state:  fusion of metatarsals
0 = unfused
1 = fused

If we plug all kinds of different animals into a data matrix consisting of
this lone character state (obviously a poor analysis, but for the purposes
of example...), then we'd probably end up with artiodactyls sharing a
closer common ancestor with ornithurine birds than either shares with, say,
pelycosaurs or basal tetanurine theropods.  No, we need to further define
what "fusion of metatarsals" means.  We could include (just for the
purposes of this example):

0 = unfused
1 = fused only proximally
2 = fusion proceeds from proximal to distal end through ontogeny
3 = fusion only distally
4 = fusion proceeds from distal to proximal end through ontogeny