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Re: Microraptor preyed on birds (official paper in PNAS)



David Marjanovic <david.marjanovic@gmx.at> wrote:


> These modifications are so weak that I wonder if they have to do with
> grasping prey (think secretarybird) and/or the small size of the animal.


Quite possibly - although comparisons between microraptorines and the
secretary bird are limited by the fact that the latter has a reversed,
grasping hallux.  Nevertheless, the use of the feet to stomp on or
secure small terrestrial prey might have been the reason behind the
modified pedal proportions of certain paravians, such as _Microraptor_
and _Archaeopteryx_.


> I'll have to try to find out if the hindlimbs are much too long for
> trunk-climbing. The lower legs in particular are unusually _long_, not short
> as expected in an animal that has parasagittal legs and needs to hold its
> center of gravity as close to the tree trunk as possible.


Good points.  However, the length of the metatarsus might have been
subject to competing demands.  After all, _Microraptor_ had rather
large 'wings' attached to the metatarsus.  A longer metatarsus allows
for a larger 'wing' (i.e., attachment of a higher number of pennaceous
feathers - around 14, I think).


> Then wouldn't we expect parachuters instead of gliders? *Microraptor* with
> its long, narrow wings looks like a glider. *Archaeopteryx* with the fairly
> wide gaps between its short, broad, round wings and its body looks like
> nothing at all.


I think I've mentioned this before, but many workers on modern gliding
mammals prefer to avoid the distinction between "gliding" and
"parachuting" based solely on the angle of descent (< or > 45
degrees).  These workers define gliding as any behavior that involves
active modulation of aerodynamic forces during the aerial commute.  So
under this definition, _Archaeopteryx_ would be a glider if the wings
were used to actively control the descent.


Matthew Martyniuk <martyniuk@gmail.com> wrote:

> For the record, Hu, Hou, Zhang, & Xu (2009) reported that the wing
> feathers of _Anchiornis_ are symmetrical. This, combined with the fact
> that the primary and secondary feathers are about equal in length with
> the proximal primaries being the longest, suggests it was less suited
> to aerial locomotion than _Microraptor_ or _Archaeopteryx_.


Check out Mike Habib's eloquent comments on the issue of feather asymmetry:

http://dml.cmnh.org/2011Oct/msg00479.html





Cheers

Tim