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Re: Hypothesis: degrees of mesopuby
In a message dated 2/15/02 6:26:37 PM Eastern Standard Time,
> In my opinion, the conclusion that opisthopuby is primitive for
> maniraptorans is erroneous. I believe the primitive state in early
> coelurosaurs was somewhat (moderately to slightly) propubic, and that this
> continued right on up to the maniraptoriform level and into the primitive
> maniraptors (early troodonts, Achillobator, etc.).
Um, the next most basal well-known troodontid (after _Sinovenator_) is
_Sinornithoides_, which is mesopubic.
Opisthopubic > mesopubic > very slightly propubic, with a concomitant
(related?) increase in body size--exactly the same as what happened in
oviraptorosaurs and large dromaeosaurs. Makes sense to me.
> Even at the Rahonavis
> and Archaeopteryx stage, it was just barely starting to shift to the
> opisthopubic side of mesopuby.
Either that, or that's where it began, with developments in various lineages
leading towards either extreme opisthopuby, continued mesopuby, or slight
> After we get past Archaeopteryx, opisthopuby is the rule rather than
> the exception. Why oviraptors reversed back to a more propubic is
> guess, but I think it is the only major reversal of this kind.
_Achillobator_? Or is this not a "major" reversal?
> The earliest Aves
> (sensu lato), such as early troodonts would have only recently evolved
> distal carpals (true semilunates), and would probably have unfused distal
> carpals until very late in ontogeny.
[eyes boggle; the water I have just drunk shoots out of my mouth Danny
Huh??? Non sequitur. The fusion of the slc (whatever that ends up meaning)
could easily have been a single mutation, possibly one that caused the wrist
cartilages to fuse before they ever even ossified. Ontogeny doesn't *have*
to recapitulate phylogeny.