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Re: Transitional Fossils



In a message dated 95-10-02 14:25:59 EDT, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

>As dinosaur-l's rampaging cladist, I would say that Archeopteryx is a great
>example of a transitional fossil,

You and I both recognize it as a transitional form, of course, but on every
cladogram I've seen it is an outgroup to the "other" birds. This is _not_
transitional. The transitional form is the _hypothetical_ common ancestor of
_Archaeopteryx_ and "other" birds. Transitional forms are _always_
hypothetical in cladograms. The closest that cladists come to admitting
transitional forms into their schemata is as metataxa--forms having no
recognizable autapomorphies but diagnosable by a unique combination of
plesiomorphies (from the "preceding" taxon) and apomorphies (from the
"succeeding" taxon). As far as I know, _Archaeopteryx_ isn't a metataxon any
more.