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Re: cursorial flapping
The problem with the interesting and not yet disproven (and very hard to disp
rove) idea that birds arose in the Triassic, is the lack of any avian
skeletons or shed feathers in the same fine grained Jurassic sediments that
preserve insects and pterosaurs until the end of the period. Complete avian
skeletons (not smashed bones) and feathers do not show up until the Late
Jurassic/Cretaceous, when they quickly become fairly numerous. This suggests
early birds were starting to fly over, fall into, and shed feathers onto,
water at this time, for the first time. The close similarlity between
Archaeopteryx, Cunfushoweveryouspellit, Sinornis and the other early Cret.
birds also suggests they arose at this time. Unless positively identifiable
bird remains start showing up in the Triassic-Jurassic, the
Chatterjee-Olshevsky hypothesis is speculative.