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Re: dinosaur/pterosaur competition
--- StephanPickering@cs.com wrote:
> (I have seen no evidence that ornithischians possessed feathers, and believe
> it improbable; it has, yet, to be demonstrated with extant fossils, how
> ornithischians and saurischians derived from the same common ancestor:
> perhaps, it was ancestors in different clades)
No evidence required - it's mandated by the definitions.
_Ornithischia_ has been defined as the first ancestor of _Triceratops_ which is
not also an ancestor of modern birds, plus all of its descendants. _Saurischia_
has been defined as the first ancestor of modern birds which is not also an
ancestor of _Triceratops_, plus all of its descendants.
When PhyloCode is implemented, it may be desirable to emend these to something
_Ornithischia_ = Clade(_Iguanodon bernissartensis_ <- _Megalosaurus
_Saurischia_ = Clade(_Megalosaurus bucklandii_ <- _Iguanodon bernissartensis_)
In either case, the two clades cannot fail to descend directly from a single
What definitions are you using for these clades?
(Agree about feathers in ornithischians being highly unlikely, but feather
homologues less so.)
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