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Re: Unfound fossil of the . . .
>Rahonavis. Yes, it's been found, but since it's arms are more
>similar to Archae than droms etc, it's missing link status will not be
>recognised until - well, what fossil must we wait for now until people
>will see it?!
I don't really think that Rahonavis can be an intermediate between
Archaeopteryx and dromaeosaurs. Rahnonavis has features like feather
papillae, an outwardly facing glenoid, proximodorsal ischial processes,
more compressed tibiotarsus, a hypopubic cup, more compressed
tarsometatarsus, and a fully reversed hallux, that dromaeosaurs lack. I
think that since it has these characters it cannot be ancestral to
dromaeosaurs. It really shows no features that unequivocally show it to
be close to dromaeosaurs.
By the way, I would like to take this moment to sorta protest the
phylogeny supported in the first "Rahona" Science paper. It resurrects
the idea that troodontids may be closer to birds than dromaeosaurs. The
idea has some supporting characters such as some of braincase features
and the proximal compression or fusion of the metatarsals; and the
seperation of the distal iscial contact. But nothing can prove that it
is closer to birds than dromaeosaurs ( and what about the rest of the
Arctometatarsalia+Bullatosauria? What shows that they are closer to
birds than dromaeosaurs?) First the arctometatarsalian pes has to be
lost to a pes that has no obvious selective advantage over it; the
prezygapophysal and chevron stiffening rods have to be evolved twice in
dromaeosaurs and birds; the opisthopubic or near-opisthopubic pubis has
to evolve twice; the pectineal process needs to evolve twice; and so on.
That's just my opinion.
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