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Re: Revising Hou et al, 96 (very very long)
Mickey Mortimer (Mickey_Mortimer111@msn.com) wrote:
<The point is that the pubic/ischial orientation is NOT simple. It is a
grade, mesopubic Archaeopteryx's pubis is more opisthopubic than
Patagonykus, which is more so than Sinornithoides, which is more so than
Rahonavis, etc.. Just like our current separation of opisthopubic from
mesopubic from propubic is arbitrary, the angles we decide to use when
refining the character will be arbitrary. Characters are all like that in
the end- you get a lot of intermediates and have to decide exactly where
to divide the grade into distinct states. By refining them, we make our
coding a more accurate reflection of anatomy.>
There is more to the pubic orientation than just the angle from the
vertical in a static horizontal pelvis, which is what most people use to
gague the orientation. However, it is true that this may be gradational,
though research goes on and I will have a page on my revamped website that
will talk about this in more detail. Does a mesopubic pelvis based on
pubic-iliac angle suddenly become propubic if the ilium rotates dorsally
relative to the sacrum as in segnosaurs, birds, and oviraptorosaurs?
Muscular position may also affect the pelvis as in opisthopubic pelves in
avians. There are more variables in this than just "regular" orientation,
such as the morphology of the proximal pubis, pubic peduncle of the ilium,
orientation of the ilium relative to the sacrum, orientatition of the
iliac pubic peduncle relative to the sacral axis, etc..
<But then you have to take into account Bagaraatan's strongly propubic
pelvis, as it's close to or barely within the enigmosaur-paravian
divergence. And explain why basal alvarezsaurids have mesopubic pelvises,
while derived ones have opisthopubic pelvises. I find a mesopubic basal
maniraptoran far more likely, judging by the condition in caudipterids and
Yes, but based on what? Most of this is limb and vertebral. The skull
is, to quote Monty Python, "Right out!". It was originally described as a
"carnosaur" as a result of this. One must, as with *Achillobator*, regard
the entire anatomy, and not parts of it and ignore the rest, to form the
hypothesis. In my undertsanding, *Bagaraatan* has hardly been a stable
posed taxon within just maniraptoriform phylogeny.
<No, I meant that I don't think it is very likely that the first
maniraptoran or first paravian was opisthopubic. I think they were more
likely to be propubic, or perhaps mesopubic.>
Why? I mean, based on what data besides phylogenetic hypotheses?
<I'm also getting irritated by people assuming Sinornithosaurus is a basal
deinonychosaur, as I feel it's quite likely an avialan (which goes a long
way in explaining why it is so birdlike).>
Don't get irritated when people have either different phylogenetic
hypotheses or disagree with you. This is a "Science marches on" thing and
taking any scientific discourse personally is the last thing that needs to
be done. It stints science. It's not as if many of the researchers
involved here actually take this stuff personally ... like me.
<I'm not sure how Sinovenator will affect things. Finally, segnosaurs are
not universally agreed to be the sister group of oviraptorosaurs (eg.
Sereno), though I feel that time is not long in coming, and the
segnosaurian status of Eshanosaurus is quite uncertain. I do think that
the precise semilunate shape of oviraptorids' fused distal carpal was
probably convergent with paravians, but that the presence of such a large
bone formed by the fusion of distal carpals I and II is synapomorphic in
enigmosaurs and paravians.>
_I_ get annoyed with "I think" statements without support or
corroboration. If it's there, I'd like to see such statements qualified,
otherwise this opinion is nest to meaningless.
Jaime A. Headden
Little steps are often the hardest to take. We are too used to making leaps
in the face of adversity, that a simple skip is so hard to do. We should all
learn to walk soft, walk small, see the world around us rather than zoom by it.
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