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Re: Regarding Phytodinosauria, Saurischia, and so forth
In a message dated 95-08-13 00:04:58 EDT, GSP1954 writes:
<< I am no longer so sure therizinosaurs are not theropods
I believe Phytodinosuria is junior to a name (Ornithosomethingorother?)
assigned to the same group by Cooper in the 80's. Our knowledge of primitive
dino relationships is still too primitive to determine the relationships and
taxonomy of major clades yet. And marasuchians sure are dinosaurs.
Judging by the feet alone, Segnosauria could not have diverged from the
theropodomorph clade anywhere above the point where pedal digit I
retroverted, that is, slightly above Herrerasauria (and certainly not within
Tetanurae). That's as close to being theropod it could have come.
Furthermore, the small, blunt teeth and downwardly curved dentary with "chin"
are commonly found among phytodinosaurs (Sauropoda, Prosauropoda,
Stegosauria, some Ornithopoda), never in theropodomorphs. The skull of
_Erlikosaurus_ can be derived fairly straightforwardly from the skull of
_Plateosaurus_, although the latter is too derived to be the true segnosaur
ancestor. The worst convergence problem is presented by the very
theropod-like forelimbs, but even those may be derived from prosauropod
forelimbs without invoking significant character reversals.
Names above family level are not governed by ICZN rules of priority.
Professional courtesy (though not pronounceability), however, might dictate
acceptance of Ornithosaurischiformes Cooper, 1985