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Re: Ah ha! That's where therizinosaurs came from
> I have long been pointing out that all flightless "theropods" with
> extensive flight adaptations are likely to be secondarily flightless because
> ... the situation parallels that of ratites etc.
On that subject I have another question:
What about furculae?
When crown group birds become flightless they quickly lose their furculae, or
retain them as splint - like, unfused clavicles.
In Dinosaurs of the Air Mr. Paul wrote that Coelophysoids were an early
ancestral stock to birds. Coelophysis has a furcula that some may regard as
virtually identical to the furcula in dromaeosaurs like Velociraptor, though
Paul sees the latter as secondarily flightless. Thus, in this scenario, the
furcula passed through the radical modification of the pectoral anatomy, and
possibly even the development of the supracoracoideus humeral elevation system,
without changing. Otherwise the furcula returned to its ancestral state.
If we can say that the similarities in the shoulder anatomy between ratites and
dromaeosaurs are evidence that supports flightlessness, then we must say that
differences are evidence that rejects flightlessness, mustn't we? Because if we
say that some differences don't matter then we can say that some similarities
Moreover, if basal birds kept giving rise to diverse flightless forms over and
over again, shouldn't at least some of them, perhaps out of random diversity,
or perhaps more likely in the most derived fliers, have lost their furculae
upon becoming flightless?
Mr. Paul, how do you account for this departure from the pattern in flightless
crown group birds? Is it possible that the furcula is an exception to the rules
of thumb about the suite of features that indicate flightlessness?
Mr. Paul will likely respond that the furcula is not an important flight
feature, since modern volant parrots also lost their furculae. But if we can
say that volant and flightless animals can have the same feature for different
reasons (the feature here being the lost furcula) then we can say the same
about all of the features that make non-avian maniraptorans appear to be