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Re: flight beginnings



Dann Pigdon <dannj@alphalink.com.au> wrote:


> If feathered limbs in early theropods developed for a similar reason, then it 
> makes you wonder
> what arboreal resource those early theropods found so valuable. It's not 
> beyond the realms of
> possibility that they too were interested in 'fruiting' podocarps.


Definitely.  The fleshy seed covering is highly nutritious, and
enticing to scansorial and arboreal vertebrates.  Are the seeds eaten
by _Jeholornis_ the result of it scampering up a tree (ginkgo?) - and
gliding back down to ground?  Same for those orangey things in the gut
of _Jinfengopteyx_.

Is this the behavior that drove the evolution of wings - raiding trees
for 'fruit', then returning to earth.  (Or stalking arboreal prey, as
in the case of predators like _Microraptor_ - there was a huge
diversity of small arboreal mammaliaforms in the Mesozoic.)
Stem-birds like _Sapeornis_ might represent a further stage, in which
theropods glided directly from tree to tree, rather than descend back
to earth.

Podocarps and other Mesozoic gymnosperms feature in certain scenarios
on the behavior of microraptorine theropods: "This high-lift,
high-drag flight strategy (Fig. 3) would have been very efficient for
leaping from moderate heights (ca. 20–30 m), consistent with tree
sizes in the Jehol podocarp forest." (Dyke et al., 2013) and
"Behaviourally useful gliding flight in cluttered environments,
especially when the flight is initiated from modest launch heights (20
m to 30 m – the likely common height of the trees found in the late
Jurassic (Zhou, Barrett & Hilton, 2003)), does not require the
complex, derived airfoils of modern birds." (Palmer, 2014).






Cheers
Tim