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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.
From: Stanley Friesen <email@example.com>
CC: firstname.lastname@example.org, email@example.com
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. firstname.lastname@example.org
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