Re: Quick cladistics question

["Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>]

Adam Yates wrote:
>As an example 
>Gauthier employed the taxon "Temnospondyli" for the stem group of the 
>modern Amphibia (ie all tetrapods closer to modern amphibians than to 
>amniotes). This is all fine, given that most workers thought that 
>modern amphibians were derived from dissorophoid temnospondyls. 
        I've said it before, I'll say it again, defining well known taxa
phylogenetically using an a priori assumption of the phylogeny can get you
in more trouble than it's worth. You're better off *defining* well
established taxa to be close to what they were erected origionally to be.
Gauthier gaffed similarly with Ornithosuchia.

>Cleary in such extreme situations the old phylogenetic definition should 
>be dropped in favour of one that is less likely to upset the content of 
>the taxon.
        And we should pay more attention to how we define taxa. See my
previous post on Allosauroidea.

> BTW de Queiroz and Gauthier never actually verbally defined these taxa, the
>definitions were implicit in their classification.
        Gauthier seems to do this a lot. I wonder if a good shorthand might
help?
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      Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock TX 79409
            Web Page:  http://faraday.clas.virginia.edu/~jrw6f