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Re: dinosaur synapomorphies? (posttemporal opening)
Ken Kinman (firstname.lastname@example.org) wrote:
<Anybody can take two taxa and use them to define a holophyletic clade. The
question is whether
they should. Clades should be named for groups that appear to have strong
synapomorphies, and to
me "postfrontals absent" cannot be defended as strong. A long list of weak
convincing to me, especially when reversals are automatically invoked whenever
characters are not congruent.>
Not true: a reversal is a shift in polarity from the derived condition to the
condition. The loss of a feature so that the preserved state is as one would
find in a more
primitive animal that did not acquire the advanced feature.
<Question. If the three dinosaur "synapomorphies" not found in sauropods
aren't reversals, and
they lie outside the Triceratops-bird defined "Dinosauria", do we then
and the public that sauropods are not dinosaurs, or do we redefine Dinosauria?>
I wouldn't see why: For one thing, you would have to demonstate that all the
connect sauropods to other dinosaurs would be an extensive case (about 15
characters or so) of
convergence, and as Pete Buchholz suggested, this is a very implausible thing.
There is so much
support for the inclusion that the three features must be considered reversed
in Sauropoda until
at such a time that a comparative and refutatory analysis can be made, then
<And I still haven't gotten any good answers to which of Sereno's dinosaur
synapomorphies are the
I will have to agree with Dr. Brochu in stating that a character lacks any
strong or weak signal
... it either is a synapomorphy, or is not. There's no middle ground.
Jaime A. Headden
Where the Wind Comes Sweeping Down the Pampas!!!!
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