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Re: Sinocalliopteryx (Theropoda: Compsognathidae) ate confuciusornithids and dromaeosaurids



Ronald Orenstein <ron.orenstein@rogers.com> wrote:

> As I have said here before, even a biped without grasping forelimbs can
> climb the right kind of tree by hopping from limb to limb (I have watched
> birds of paradise do this in New Guinea).  However, this involves the
> ability to perch (depending on the limb) and, probably, the ability to hop
> (though I do not know of any specific anatomical correlates with hopping,
> and closely related passerine birds (in the same genus) may use one or the
> other as their primary means of getting around on the ground.


The lack of a prehensile manus or pes is a huge obstacle to the notion
that _Microraptor_ was a specialized arboreal quadruped or biped -
such as a canopy-dweller.  I could entertain the notion that a small
theropod could clamber through branches quadrupedally without a
perching pes, if the manus was adept at grasping and could take up the
slack.  But the manus wasn't adapted for grasping objects
one-handedly, so its ability to grab branches was poor.  Add to that
the restricted ranges of motion at the joints, especially the wrist
and ankle.  _Microraptor_ was no arborealist, and no percher.  (Same
goes for _Archaeopteryx_.)


It's also worth mentioning that in today's world some birds feed on
cycad seeds.  But they don't nest in cycads, and AFAIK don't really
roost in the crown.  The birds just perch in the crown of the cycad,
eat the seeds, and move on (bats do the same).  Small non-avian
maniraptorans may have done the same - except they accessed the seeds
by climbing the trunk, not from flying in, as small non-volant mammals
do today.  Given the prevalence of cycads (and other cycad-like
plants) in the mid-Mesozoic, this behavior might have been a driving
force for tree-climbing among small maniraptorans.  Cycads are often
sparsely branched, so prehensile ability would not be all that useful
for scaling the trunk.  Once at the apex of the trunk, they could
probably stand there to feed: no perching necessary.  How did the
little maniraptoran get back to the ground?  Parachuting or gliding,
perhaps.



BTW, I envy your experiences watching birds-of-paradise In New Guinea.






Cheers

Tim