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Re: "Flight theory has legs"
Scott Hartman <DinoBoyGraphics@aol.com> wrote:
Ok, so the results are preliminary and need to be confirmed, perhaps
further study will show otherwise, but common [sic] guys, you are really
special pleading to shoe-horn the current results into the trees-down (or
trees-sideways) idea of flight origins.
I would say that the morphologies of _Microraptor_ and _Cryptovolans_
require very little "special pleading" to be shoehorned into (a) an arboreal
or (b) a gliding ecomorphology. What's the difficulty? the fit appears to
be very comfortable.
Dinobirds leaping from branch to branch would be in dire need of pedal
claws for grasping the branches the landed on.
Excuse me, but never once did I say that arboreal/scansorial maniraptorans
leaped from tree to tree, or from branch to branch. The evidence favors
descents from trees to the ground on the part of small-bodied,
The condition is made worse because their long columnar limbs put their
center of gravity further away from the branch, decreasing mechanical
advantage for stopping their momentum.
Please show me your calculations for estimating the center of mass (CM) in
I would also add that, as demonstrated by Gatesy and others, the most basal
birds retain primitively long hindlimbs that are strikingly
dromaeosaurid-like in their proportions. This includes _Sinornis_, which
had a highly specialized perching pes.
Archaeopteryx and other dinobirds may not have even had a fully retroverted
hallux, and they certainly did not have the large flexor tubercles and
curved pedal phlanges needed for such scansoriality.
Well, perhaps the fact that they had arms and hands to help them climb
alleviated the need for a specialized grasping pes. _Archaeopteryx_ (at
least) does appear to have had a fully retroverted hallux.
I know that a trees-down origin is more intuitive,
Intuitive, schmuintitive. A "trees-down" origin of birds is corroborated by
anatomical and phylogenetic evidence, and is at least as strong as the
"ground-up" scenario. BTW, as has been argued many times on this very list
(by myself, among others), there's no reason why these two scenarios
("ground-up" vs "trees-down") should be considered mutually exclusive.
and I've convinced that both bats and pterosaurs evolved flight in an
Intuiton is all we have in the case of pterosaurs and bats. There are no
known (or recognized) fossils of non-volant sister taxa to either the
Chiroptera and Pterosauria.
but dinobirds are very different.
Yes, they have a fossil record - which includes scansorial, aerial taxa such
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