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clarification




Stanley,
I pretty much agree with all your statements on the paraphyly of Thecodontia. But I am indeed a taxonomist of Mayrian stripe, and taking Peter Ashlock's systematics course at the University of Kansas back in the 1970's had an immense impact on how I practice systematics. Your last statement below makes the assumption that one is recognizing the traditional Thecodontia (sensu stricto).
However, in an effort to make Thecodontiformes ("Thecodontia" sensu lato) as useful as possible, I include prolacertiforms and rhynchosaurs (and still haven't decided about choristoderes). Therefore, Longisquamidae and Sharovipterygidae will end up in Thecodontiformes whether they are prolacertiforms or closer to true archosaurs. Likewise, Pterosauriformes evolved directly from Thecodontiformes, whether pterosaurs evolved from true archosaurs (traditional view) or from prolacertiforms. I hope this clarifies my position.
By the way, if someone wants to apply Ashlock's methods to see if my Thecodontiformes "measures up", I would be interested in the results.
------Ken Kinman
********************************************************
From: Stanley Friesen <sarima@friesen.net>
Reply-To: sarima@friesen.net
To: twilliams_alpha@hotmail.com
CC: kinman@hotmail.com, dinosaur@usc.edu
Subject: Re: DEFENDING MODERN BIOLOGY
Date: Wed, 21 Jun 2000 22:31:52 -0700

At 12:06 PM 6/21/00 -0400, Timothy Williams wrote:

Now that you mention it, it WAS a polyphyletic trash-can.  The Thecodontia
became a receptacle for any Triassic reptile that appeared to be an
archosaur and did not appear to be a dinosaur, crocodilian or pterosaur.
I've seen _Longisquama_, _Sharovipteryx_ (_Podopteryx_) and _Hupehsuchus_
all shoehorned into the Thecodontia.

Saying this makes _Thecodontia_ polyphyletic assumes that one accepts the cladograms that put these animals in or near the Prolacertiformes. Just about everybody I know of who put them in _Thecondontia_ believed they were shared a closer common ancestor with _Proterosuchus_ than with any prolacertiform. Given such a family tree, a Thecodontia including them is paraphyletic, not polyphyletic.

I agree that recent evidence favors a prolacertiform position for these genera. But any taxonomist of a Mayrian stripe would take this as a
sufficient reason to *remove* them from _Thecodontia_.


--------------
May the peace of God be with you.         sarima@ix.netcom.com

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