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Re: Microraptor also ate fish
In a message dated 5/1/13 6:55:33 PM, email@example.com writes:
> The problem is that there is no way to ever sufficiently understand the
> flight performance of microraptors.
It also depends on to what degree the humerus could be elevated above
the dorsum, which in turn depends upon the orientation of the shoulder
joint. No recovery stroke, no wingbeat, no powered flight.
-- As per previous discussions on the list, the argument that vertical
humeral elevation is needed for some form of powered flight is very dubious.
well preclude strong flight climbing ability though.
> That it was a powered flier is the greatly
> superior hypothesis because it had so many adaptations for supporting
> large arms muscles and anchoring the primaries, well beyond those found in
> Archaeopteryx which itself was beyond just gliding (I've discussed this in
> the literature and won't repeat it here because that is not the specific
These interpretations aren't as simple as you make them seem.
_Velociraptor_ has quill knobs, suggesting that it had forelimb
feathers that were firmly anchored to the bone. So firmly-anchored
feathers can't automatically be counted as a flight-related character.
-- Velociraptor does not have a flattened central finger to firmly anchor
the more important distal primaries that microraptors do. The presence of
flight features in large derived dromaeosaurs is the same pattern seen in
secondarily flightless birds. It has never been shown that these features
before flight, they are very probably the result of flight.
And "large arm muscles" can hardly be a flight-related feature in all
theropods, considering that many theropods used their forelimbs for
catching and holding prey. I don't dispute that powerful arm muscles
are essential for flight (!). But we can't assume that this feature
originally evolved for flight in theropods.
-- The big dromaeosaurs did not have arm muscles as proportionally large as
those of microraptors because the former have smaller arms (the humerus is
half the length of the body in microraptors, much less so in Velociraptor)
with smaller muscles. Only the Jehol dromaeosaurs have arms large enough to
be muscled well enough for powered flight (maybe juveniles of big
dromaeosaurs had some flight ability, would be nice to have some skeletons to
is going on with them).
> But could it climb well enough to get into tree
> canopies from the ground on a regular basis? Very possibly no, be we can
> never know.
I'm not clear on why the ability to penetrate tree canopies would
necessarily be so important. Recall that at the time of the Jehol
biota, angiosperms were still getting off the ground, and
"cycadophytic" plants were far more prevalent than they are today.
The latter offered elevation and potential food sources, but little or
nothing in the way of shelter or refuge.
-- MY understanding is that the Jehol flora was conifer dominated and
closed canopied, so there were mainly high canopies rather than cycad type
to fly up into.
> What I do know is that having examined a number of big format photos of
> Microraptor central toe claws that were kindly supplied to me, that they
> (using the recent published data sets and my own on a large set of
> birds) more strongly arced than the claws of any livng bird that reguarly
> traverses ground by walking hither and on. Only birds with weakly curved
> central toe claws walk and run a lot (I've sampled them, including the
Is this pronounced claw curvature unique to _Microraptor_ among
non-bird theropods? Or could a large dromaeosaur like _Deinonychus_
have the same or similar claw curvatures to _Microraptor_? I think
it's helpful to look at _Microraptor_'s features in the context of it
being a predatory theropod, not just a bird relative. As noted in the
literature, most of the vaunted "arboreal" characters in _Microraptor_
(including foot characters) are also found in _Deinonychus_.
-- Keratin sheathes are never preserved in large dromaeosaurs, but the
chance that they were as curved as those of microraptors is zero. All small
terrestrial theropods and Mesozoic with preserved toe claw sheaths are low
curvature, and no known bird incl raptors that spends much time walking and
hunting on the ground has such strongly curved toe claws. The central toe claws
of Veloci and Deino would have been fairly flat and probably tip worn, like
those of ratites and secretary birds (looked at them in the Smithsonian
collections - because their toe claws are blunt Secbirds pummel their prey to
death, rather than try to claw pierce it).
> So Microraptor either used flight as it's main means of moving about from
> one place on the ground to another (doubtful in view of probably limited
> powered flight abilities, and probable lack of many open spaces in the
> forests) or was primarily an arboreal climber (very probably, considering
> lived in apparently dense woodlands).
I doubt that the lack of open spaces prohibited _Microraptor_ from
moving about on the ground. It just meant that there was no point in
being highly cursorial.
-- Again, no bird that moves much on the ground has strongly curved toe
claws, they are always flattened. No known exception. The strongly curved toe
claws of microraptors mean they were not habitual ground walkers. The big
foot feathers would not be good for that either. Could do it if they needed to,
but they were not adapted for it.