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Re: pterosaur femora sprawl
Why not? If they are...(even upside down) they are! Don't expect them
to walk bipedally though.
I don't consider resting pose to be a gait. When I use the term
bipedal I refer to running or walking. So yes, bats hang in a
"bipedal" fashion. But, since is is not a locomotor gait, and given
that the hind limbs are not adapted to bipedal walking, I find your
assumption that "bipedalism" was important for flight evolution in bats
a bit odd - if you're correct about the "freeing" of the forelimbs,
then only having them freed while sleeping seems insufficient.
Bats are civets. So are Ptilocercus and dermopterans, according to
cladistic analysis. They haven't been tested against each other yet in
According to your phylogenetic reconstruction, yes. But there are
several competing cladistic analyses. You admit yourself that
molecular support has yet to be gleaned - what if that differs?
No problem there. Same with humans. Same with 19 lizards capable of
bipedalism. Same with pterosaurs. I have no doubts that Sharovipteryx
and Longisquama bellied up to some tree trunks too.
Ah, but even facultatively bipedal lizards actually use the hind limbs
for a true gait (ie. sprinting). Maybe pterosaur ancestors did the
same thing - I'm not saying they didn't (though I see no reason to
assume that they did, at present). However, I doubt that bat ancestors
BTW, don't forget, bats climb with their thumbs -- also a departure
from tetrapod norms. So, probably secondarily adopted.
Actually, I suspect the departure comes from the lack of use of the
other four fingers in climbing. Same effect, different polarity.
In fact, bats have
essentially arboreal limb proportions and structural strengths
(especially pteropodids): they are quantitatively like suspensory
primates in the forelimb structure from the shoulder down to the
No problem. So are humans.
Humans actually walk bipedally, though. My resting position is laying
down, but I wouldn't say that I share a gait with squamates. Again, I
agree that the hanging adaptations in bats are important, I just fail
to see why they are necessary for the evolution of wings.
Not true. Sharovipteryx, a pterosaur relative, would disagree with
you. And when you repair the pterosaur stance, aligning all the axes,
bringing them back into more typical tetrapod configurations, then
you'll see the shoulder glenoid is aligned above the toes, as in
birds, the pelvis is elongated, as in birds, the tarsus has a nice
trochlea, as in birds, and you'll see that pterosaurs, especially the
early ones with short metacarpi, were fully capable of hind limb
True, a small pterosaur could facultatively launch bipedally. However,
I see no reason to expect that this was their normal mode of launch.
Quad launching would be more effective for them, and their structural
scaling patterns demonstrate that quad launching is the more likely
standard method for nearly all sizes of pterosaur - thought it only
becomes the obligate state at large sizes.
.Bennett followed von Huene is proposing a hind limb leaping arboreal
origin for pterosaurs. That has not been disputed in print.
True. Note that animals can leap quadrupedally, though, and this has
little effect on his overall model. I think hind limb leaping was
assumed because the bipedally launch model has been intrenched for a
I know J. Cunningham is fond of the forelimb launch in Q. but he or
anyone else has yet to put a storyboard together on how this happens.
I'm curious as all get-out to see it too. Not saying it doesn't
happen, but if so, it was not the ancestral way.
Jim is not alone in this; I have a paper in press on the structural
evidence for quad launch in pterosaurs, and have more on that in the
works (he and I came to the same conclusion, separately, through
different means some time ago). I'm not sure what you mean by
"storyboard", but if you mean the launch kinematic, then Jim actually
has worked it out, as have I (though Jim worked it out in more detail,
and prior to myself). Quad launch was almost certainly not limited to
Quetzalcoatlus. The structural strength ratios, body size trends,
walking stance, muscle builds, and trabecular bracing of pterosaur long
bones all indicate that most species quad launched as the primary take
off dynamic. Small species could facultatively launch bipedally, if
need be, but quad launch would be more rapid and efficient. I suspect,
therefore, that quad launch was basal to pterosaurs proper. That said,
if the nearest relatives of pterosaurs do turn out to be bipedal, then
it may be that the ancestral state (in the stem group) was bipedalism,
as you indicate. At present, I am not convinced that this must have
been the case, and if it was then the switch to quad walking/climbing
and launching occurred very early in pterosaurs.
Are you referring to branch support methodologies?
Yes and beyond. Whatever you want to throw at them.
Fair enough. In that case, what branch support algorithms have you
used so far? What sort of nodal support do you get? Have you done any
sort of sensitivity analysis regarding character assignment/use?
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181