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RE: Peering at review
Dino Guy Ralph wrote:
> > In BCF, modern birds all fall into the clade Maniraptora. I just
> > disagree with the idea that the basal maniraptoran was a large
> >(Deinonychus-size), cursorial animal.
> Whether your hypothesis has merit, I have to ask: who is proposing this?
> What recently published scenario requires basal maniraptoran bird
> ancestors to be large animals?
Indeed. Those taxa that lie closest to the base of the Maniraptora are
usually the *smallest* known representatives of their respective lineages
(birds being the exception). Oviraptorosaurs, therizinosaurs and
deinonychosaurs all became larger in the mid-late Cretaceous; but all appear
to have had more humble beginnings closer to the Jurassic-Cretaceous
boundary. The preponderance of evidence suggests that small body size was a
basal maniraptoran trait - and perhaps scansoriality as well.
> That's just it. They >don't< require it, yet somehow we've all read
> those accounts of how Deinonychus-like dinosaurs became smaller, went
> climbing up into trees, and evolved into birds.
I credit the change in thinking on this issue as due to the discovery of
small-bodied primitive maniraptorans (_Microraptor_ etc), rather than the
impact of BCF. As Ralph says, the BCF scenario certainly has merit; but
regarding each and every theropod dinosaur as either arboreal or secondarily
terrestrial is stretching the evidence beyond breaking point.