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Whoa! Dont' get me mixed up with Bakker. I do not recognize any taxon
based on something as flimsy and speculative as warm-bloodedness. Mammalia
should be based on the three ear ossicles, and luckily that's what most
mammalogists do base it on. Aves is a little trickier, being mired in all
this controversy, but warm-bloodedness certainly is not a candidate as a
The crocs and turtles and rest of the "reptiles" didn't diversify
anywhere near the extent that birds and mammals did, so they have never been
seen as candidates for elevation to class status. If birds had died out at
the K/T extinction, I would classify them as another order of reptiles, but
that didn't happen.
And like it or not, these early thecodonts are going to problematic for
a long, long time, so I'm not abandoning Thecodontiformes any time soon.
And as for Sphenosuchidae, I show it as sister group to Order
Crocodyliformes. Is the phenetic gap between Sphenosuchidae and
Poposauridae all that much bigger than the phenetic gap between
Sphenosuchidae and Protosuchidae? If so, I'll consider making
Sphenosuchidae the basal clade of Crocodyliformes. No big deal to me. I'll
ask Chris which he prefers.
From: "Timothy Williams" <firstname.lastname@example.org>
To: email@example.com, firstname.lastname@example.org
Subject: Re: Archosauromorph classification & Thecodonts
Date: Wed, 21 Jun 2000 15:57:58 EDT
Ken Kinman wrote:
Actually I have been asking around for opinions on whether I should
include choristoderes as well, and if so, should they be placed as (1)
sister group to rhynchosaurs; or (2) as sister group to rhynchosaurs plus
all the rest of the thecodonts.
This came up recently:
different than Class Reptilia being all amniotes minus their mammal and
descendants, but being paraphyletic I guess you would call that a
Yep, I would regard "Reptilia" as a trash-can. At least under the
definition (as opposed to "diagnosis") under which birds (Aves) and mammals
(Mammalia) are excluded because they are "warm-blooded". Crocodiles are
more closely related to birds than to turtles, yet the crocs are lumped in
with the turtles. Mammals get their own class, yet pelycosaurs have to
stay behind in the Reptilia because they weren't clever enough to evolve an
endothermic metabolism. Etc.
But as far as "trash-cans" go, Dinosauria and a lot of other groups
have had problematic groups thrown into them which were later removed.
Yes, but the difference is that the "Thecodontia" seems to be specifically
designed to *accommodate* problematic taxa. Any archosaur that wasn't a
dinosaur/crocodilian/pterosaur was stuck in the Thecodontia. Non-dinosaurs
are occasionally assigned to the Saurischia and Ornithischia, but these are
removed when their true affinities are realised. With thecodonts like
_Lagosuchus_ and _Sphenosuchus_, you seem intent on keeping them among the
thecodonts *despite* the fact that their closest relatives have been
identified (and they're *not* thecodonts).
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