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Cladospeak (Mammalia, Crurotarsi)
Jaime and David,
First to David. My clarification, using proper "cladospeak": if
ornithosuchids are closer to birds than to crocs, then Crurotarsi probably
becomes a junior synonym of Archosauria, but it would still need to be
abandoned (or shall we nitpick about the word "abandoned" as well).
Cladospeak reminds me of lawyer-speak, and by the time you get through
defining and clarifying, the original point is totally forgotten. And I'm
not sure how "strong synapomorphies" might differ from "significant
syanpomorphies", but someone fluent in cladospeak might explain it. I just
hope we don't reach to absurd level of defining what the meaning of "is" is.
:-) Anyway, more on Crurotarsi below.
Bur first a clarification for Jaime--- I use the traditional,
character-based, Mammalia (sensu lato) that most mammalogists still use. We
do not need to be educated, we simply ignore (as best we can) the strictly
cladistic equivalent (Mammaliformes, which has caused confusion ever since
it was proposed). Sinoconodonts, morganucodonts, docodonts, triconodonts,
multituberculates, are all primitive mammals (sensu lato), although the
order in which they split off from one another is controversial.
The sister group to Mammalia (sensu lato) is the eucynodont ("derived"
therapsid) family Trithelodontidae, which had not completed the transition
to the mammal jaw joint and associated movement of the three ear ossicles.
[is "derived" better than "advanced"?---or are they both a cladospeak
faux-pas, no-no, bad-bad].
This is a "significant" synapomorphy (to use your terminology), or
strong synapomorphy in my parlance. It is so significant (i.e., so
"strong") that most mammalogists continue to use this as their definition of
mammal (Class Mammalia), and the cladistic Mammaliformes and "crown group
Mammalia" are just irritating and confusing hinderances to communication
which resulted when cladists decided to fix something that wasn't broken in
the first place. And BTW, neontologists use morphology too (at least a lot
of us still do).
As for Crurotarsi, I am not saying "it MUST be bad". I am saying the
synapomorphies supposedly supporting it as a clade do not appear significant
(i.e. not strong), and compared to the mammal synapomorphy, they are
downright "weak" (comparatively insignificant). Therefore I am saying
Crurotarsi "MIGHT be bad", so I am encouraging people to take a harder look
at it instead of just repeating Sereno and Gauthier's synapomorphy lists
like they have it all figured out already. If those who plan to defend
Ornithodira sensu stricto (contra Dave Peters) plan to use Sereno's
Crurotarsi synapomorphies as a given, then I think they may be basing their
arguments on an insecure foundation, and perhaps even sliding down a
slippery slope of circular reasoning. I assume the pro-"Ornithodira sensu
stricto" arguments have not yet been expressed on the web, so I guess we'll
just have to wait for the paper (whenever that might be).
P.S. I might add that plesiomorphies and convergences are "observed", just
as synapomorphies are. However, assigning these observed characters to a
synapomorphy list is in the mind of the beholder, and such lists are
created. I just think too many people take it for granted that these are
synapomorphies just because Gauthier and Sereno agreed on them (or at least
most of them). I might even come to the conclusion that their
synapomorphies for Crurotarsi and Dinosauria are strong when taken together,
but since noone seems to be willing to say that some subset of those
"synapomorphies" are more significant (or stronger) than others, it
certainly will take me that much longer to come to a decision.
I am reluctant to say who may or may not still regard Ornithosuchids as
closer to birds than to crocs (as views change so rapidly sometimes), but I
believe Michael Benton still favors this toplology. And I believe Dave
Peters also favored this topology (not sure if he still does). However, I'm
not going to rattle off a long list of people who probably still favor it,
but there are enough that I think it's still rather iffy which way the
ornithosuchids will go, and Crurotarsi could easily end up a synonym of
Archosauria. Lewisuchus may be just a sign of things to come.
From: "Jaime A. Headden" <email@example.com>
CC: firstname.lastname@example.org, email@example.com
Subject: Re: synapomorphies not "being" equal
Date: Mon, 3 Sep 2001 03:10:28 -0700 (PDT)
Ken Kinman (firstname.lastname@example.org) wrote:
For one thing, synapomorphies are not created, they are observed. There
_are_ features that
unite two forms on a morphological paradigm, these being synapomorphies. I
do recall that you are
a neontologist and appear to be more familiar with genetic paradigms rather
ones. Morphology does give us a different framework to operate in.
<I've been thinking very hard about this, and I am still not convinced that
all synapomorphies are
created equal. Some are "stronger" than others no matter how long or big
the evolutionary gap
happens to be in which it falls.
In my opinion, the one synapomorphy of Mammalia, the movement of the
three ossicles from the
mandible into the ear of the first mammals, was strongly selected for and
rapidly. It is thus a very strong synapomorphy.>
Yes, it is a significant synapomoprhy. However, there are more than one
Mammlia, but this depends on what group you call Mammalia. If you are
referring to all eucynodonts
with three middle ear ossicles, then this is a broad category indeed, and
would include a good
deal of fossils (*Prokennalestes*, *Kuhneotherium*, etc..). However, as you
note, you'd rather not
<This almost cries out for the need for these purported synapomorphies to
be evaluated, and that
the strongest be identified and carefully scrutinized. The
therapsid-to-mammal transition is just
as well documented (if not more so) as that of the transition to
"non-dinosaurs" to dinosaurs.
Therefore the lack of a strong synapomorphy in the latter should be taken
as a strong signal that
a comprehensive reevaluation is required. The question is who will be the
"Dave Peters" of
So far, Paul Sereno, whose work has been somewhat in part revisionary of
interrelationships and (especially with Novas) the origin of Dinosauria.
Novas has been working on
dinosaur origins after Gauthier and before Sereno was, and came to the same
conclusions as did
Gauthier, and Bakker and Galton back in 1985 (before Gauthier's findings
were published). Or are
you trying to find someone to realize your hypothesis of a paraphyletic
<I believe than Crurotarsi will probably not survive, and it is still a
toss-up whether Dinosauria
will survive as a clade. Therefore those who have challenged me to come up
with an alternative set
of synapomorphies will have to wait for me to catch up or hope that those
that those who need less
"catching-up" will rise to the challenge. I would prefer the latter, since
I have other projects
that need attention, and strongly suspect that at least one of them will
will rise to this
challenge. All I can say is the sooner the better.>
Then you enter this game with loaded dice, Ken. Saying something to the
equivalent of "Crurotarsi
doesn't look real to me, it must be bad." This is not science.
Jaime A. Headden
Where the Wind Comes Sweeping Down the Pampas!!!!
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