Re: Strange thoughts on PN - was Re: BAD vs. BADD

[Nick Pharris <npharris@umich.edu>]

Quoting Mike Taylor <mike@indexdata.com>:

> Think carefully about why you would want to talk about a group such as
> Tetrapoda.  What would it gain you?  In most ways, _Acanthostega_ is
> much more similar to _Panderichthys_ and _Tiktaalik_ than it is to
> _Mus_, and that fact is *obscured* by the recognition of a formal
> taxon equivalent to "tetrapods".

Not necessarily.  It is assumed that the first branches in any clade 
(e.g. Tetrapoda) will share certain similarities with organisms just 
outside that clade (e.g. _Panderichthys_ and _Tiktaalik_) -- that is, 
after all, the definition of being relatively underived within one's 
clade.

Under a Linnaean-type classification (one group for "fish" and a 
coordinate one for tetrapods, perhaps combined with a statement to the 
effect that tetrapods are derived from "fish"), you might infer that 
basal tetrapods are the tetrapods most similar to "fish", but the 
classification tells you nothing about *which* "fish" they are most 
like (and, conversely, tells you nothing about which "fish" are most 
like tetrapods).

A PN classification, recognizing Tetrapoda, nested within 
Tetrapodomorpha, nested within Sarcopterygii, and so on, neatly 
encapsulates all of this information.

--
Nick Pharris
Department of Linguistics
University of Michigan

"Creativity is the sudden cessation of stupidity."
    --Edwin H. Land