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Re: Fwd: Are dinosaurs really reptiles? (2)
On Sun, Apr 27, 2008 at 9:44 PM, David Peters <email@example.com> wrote:
> I'm seeing a pattern here: Small, flat-headed and short-toed gives rise
> to big,
> and short-toed. There's some logic to it. The intertemporal is gone. So
> this must be an
> amniote.Or is it? A fat, slow, plant-eater is the father of us all?
It's a stem-amniote, not an amniote (i.e., it's not part of the crown
group). As to whether it's an "apo-amniote" or not (i.e., as to
whether embryos had an amniotic sac), I'm not sure that we know.
Why would you say "father" when it's probably more like "uncle" or "cousin"?
> The pattern of giant, weird, plant-eaters continues. So it must be
> No doubt this is an amniote [representing the Synapsida?].
> Suddenly we're aquatic! With a decidely long premaxilla! And long
> And a long tail. And a long neck. And long toes! So derived! So early!
> This one seems misplaced.
It's a side-branch, not an ancestor. (Repeat this for everything in the list.)
> Another close cousin. Say, isn't this fanged taxon getting
> uncomfortably close to
> the Synapsida? But didn't we leave those guys way back yonder with
I'm a little outside my area of knowledge here, but since when is
_Protorothyris_ a synapsid relative? I've never seen it as anything
but a sauropsid.
> Suddenly, after all these 'anapsids' a diapsid! Two holes at once! Isn't
> it interesting that he
> went straight for two, rather than dawdling about with one or the other
> for awhile?
What prevents the final common ancestor of _Cephalerpeton_ and
(crown-)_Diapsida_ from having existed a good while before the final
common ancestor of _Petrolacosaueus_ and (crown-)_Diapsida_? (On
another note, how long does it take to evolve cranial fenestrae,
anyway? Do we even know?)
> that's not all. Long toes. Long limbs. Long neck. Long tail. Sharp
> teeth. The only taxon on this l
> list, other than Araeoscelis [and Anthracodromeus] who remotely
> resembled this one is
> Mesosaurus...way... back ...yonder. [shudder]
Presumably other characters outnumbered those five (all of which are
pretty damn homoplastic).
> yes. A good sister
> line: Credit is given where credit is due, but this seems to be very
> scattered famiy tree. I don't have any problem with big lumbering plant
> eaters giving rise to gracile little insect-eaters or visa versa... but the
> change ought to be gradual. Evolutionary. Not like this see-saw.
The plant eaters are most likely derived sister taxa, not ancestors.
> Next question: What were the five to ten sister genera leading up to
> Herrerrasaurus? No suprageneric taxa please. And please include at least one
What is a "sister genus"? You mean "sister clade"?
T. Michael Keesey
Director of Technology
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Los Angeles, California 90039