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Re: Pterosaur wings and refs



David Peters and David Unwin wrote:
> 
>> Add to this Hazlehurst's (1991) discovery of a good correlation between fore 
>> and hind limb length in pterosaurs,
> 
> This is probably true because in a balanced standing bipedal pose the
> distal metacarpus of nearly all pterosaurs will touch the ground, or at
> least the ankle, by simple elbow extension (short-armed Austriadactylus
> and Campylognathoides zitteli are the sole exceptions).

But there are exceptions, implying non-bipedality in at least some
pterosaurs.  In the animals I mess with, I've never seen much need for a
balanced standing bipedal pose, though they might be able to achieve one
till the first puff of breeze poofed them over on their fanny.  I think
we're still at the point where we can't say that all pterosaurs were
quadrupedal all the time, nor that some pterosaurs were bipedal part of
the time.  More info is needed in that regard.  When we sized the
missing long bones for the Q northropi sculptures, we lengthened the Q
species hind legs by a factor of 2.27 so that the big animal would
maintain the same torso posture while in a quadrupedal position on the
ground.  Needless to say, that was pure speculation on our part, and we
left the femur/tibia length ratio unchanged from species to make it more
obvious what we had done.

> Thus pteros were able quadrupeds and bipeds,

Some may have been able bipeds.  I don't believe that all were, and do
believe that it is possible that none were.  I don't think we are at the
point yet of being able to exclude possibilities.

> _even better_ than the frilled lizard and
> her 18 extant sisters who can morph in moments from a cold-blooded
> undulating quad into a speedy, digitigrade biped.

This reminds me of a likely motor-glider mode for Quetz flight.... long
periods of soaring interupted by the occasional flurry of 1 to about 20
anaerobic flaps.  Requires relatively little aerobic ability and helps
with the dead air problem in the long neck.

> I can send Internet links to mpg movies of same if interested.

I'm interested, but my antequated computer craps out on mpegs.  I'd like
to have the links anyway.
> 
> >>the general similarity of appendicular morphology across a wide
> range of taxa, including all those with direct evidence of
> brachiopatagium attachment to the hind limbs,

Does this imply the trailing edge spacing of about 40-45% of the humerus
length at the elbow for all these species?  If so, it's not all that
different from my speculations (since there is no soft tissue
preservation in Quetz, all hypotheses regarding Quetz planform are
speculative and based on indirect evidence).

> and one ends up with a clear, well integrated
> picture of whats going on in pterosaurs vis a vis wings and legs.

I agree with the statement, but unfortunately, our conclusions are still
somewhat different.

> quadrupedal plantigrady - as shown y thousands of pterosaur tracks,

In this regard, I agree wholeheartedly.

> and is supported by a new study by Matt Wilkinson (Cambridge) showing how
> effective and aerodynamically advantageous wing attachment to the hind limbs 
> was
> for pterosaur flight.

It can be made to work quite well in smaller, short necked pterosaurs. 
In larger ones, I'm not sure that it is quite as versatile or efficient
as the more independent arrangement (which can be configured to
mechanically approximate the broad configuration, but can also be
configured to open up as an inboard single-slotted Fowler flap), and in
that case there might be some trend toward independence in the big, long
necked guys (say 3-4 meters span and up, as a guess).

> Since no one has ever presented any evidence, direct or
> indirect to show that the brachiopatagium was not attached to the hind
> limb, in any pterosaur,
> 
> Just a few more weeks you'll have it.

I look forward to seeing it too.

> I thought of you, David, often will writing the paper.
> Fasten your seatbelt. You're in for a paradigm shift.

I don't think so.  I think that DU is probably right about the hindlimb
connection in some pterosaurs, and that DP is probably right about the
lack or partial lack in others.

>>Reconstructing, the exact shape of the brachopatagium, as it was in life, is 
>>more
> problematic in that its not clear how extensible it might have been 
> originally.

Boy, you got that right.  Particularly since it seems that the chord is
actively variable, but is not clear quite how variable (with either
connection scenario).  Eventually, I think enough information will turn
up that we will have a better idea of extensibility.

Dave Unwin, do you have a good feel for the connective tissue
interconnections between the actinofibrils and their freedom to shear
relative to one another?  So far, I have nothing but hunches in that
regard.

Hang in there, guys.  I think you're both doing good work and am really
looking forward to where it goes in the future.