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Re: Water-bourne pterosaur launch and albatross take-offs
----- Original Message -----
From: "David Peters" <firstname.lastname@example.org>
To: "dinosaur mailing list" <email@example.com>; "jim cunningham"
<firstname.lastname@example.org>; "Mike Habib" <email@example.com>; "Mark Witton"
Sent: Wednesday, October 07, 2009 6:50 AM
Subject: Re: Water-bourne pterosaur launch and albatross take-offs
Given the fact that, with the one example we do have in the ichnite
literature, that at least one pterosaur could perform a perfect two-point
landing, then put its other two down for terrestrial progression, it
makes one wonder what the difference is?
The difference is in the effectiveness of their use of full alternating
momentum reversal during the final stages of the approach to touchdown.
The uropatagia would make nice airbrakes.
But are on the wrong end of the animal for appropriate control of the
pitching moment while doing so. Don't get me wrong; they do serve that
purpose to a consderable extent, combined with appropriate average placement
of the wings and orientation of wing thrust relative to the cg -- so that
the wings are doing more of that job than the uropatagia are. But by the
time of the touchdown itself, the uropatagium is unloaded so that the legs
are unimpeded in their fore and aft movement.
Too much airspeed on landing seems to be the albatross problem. Not
enough airspeed to gain flight seems to be their problem on take-off
using their feet and wings. So maybe the albatross model is not so good
Some pterosaurs apparently were able to come to a complete stall-stop
before touching down.
As can some birds, using full alternating momentum reversal. I wouldn't
call it a stall though, since they are not stalled, albeit that they are
going more slowly than steady-state stall speed.
Does that fact give us any clue to their wing- flapping take-off
No. Full alternating momentum reversal doesn't provide enough thrust for
liftoff. Just enough for settling in.
Yet another video "Albatross takes flight" shows us one on a rocky
outgroup, too rocky for a run, so it elevates its wings, pushes off once
with its legs, flaps, rises and soars on incoming breezes. This video
makes a major point. If pterosaurs were going to land on a flat surface,
they, like the albatross, probably knew when and where breezes were
available for wind-assisted take-off and predators were not likely to be
No doubt they did.
Those that failed became extinct.
That's wrong. They didn't need the winds or the elevation to takeoff, and
even from a flat surface in a dead calm, the larger pterosaurs were already
moving faster when their hands left the ground than their predators were
able to run. About the only way for a land predator to capture a pterosaur
would be an ambush from the front quarter, or an ambush from any direction
when the direction ahead of the pterosaur was obstructed. My hunch is that
pterosaurs on the ground tended to orient themselves with open areas ahead
of them. I've been thinking about doing a sketch of a rear quarter view of
a pterosaur in the midst of a turning takeoff (one hand still on the ground.
but both legs clear and already in turning flight position) while in an
effort to escape an on-rushing predator coming in from the front quarter.
Albatrosses cannot land in trees, evidently, or trees are not present on
the islands they frequent, but trees were available for pterosaurs of all
I'm having some trouble imagining a Hatz, Qn, or Aramb perched in a tree.
Sure would be a big tree, and why bother when you're pretty much predator
proof anytime you're in a reasonably open area?
Grappling claws on wings (palms facing medially!) testify to their
Do me a favor and sketch me a Hatz climbing up into the upper branches of a
Since the uppermost branches are likely to be unable to support the
1200-1500 pound loads that the pterosaur would impart to them during the
launch process, the big pterosaur would also need to find a tree tall enough
that he could gently hop or drop out, gain flying speed from the fall due
to gravitational acceleration, then pull out of the high speed dive before
impacting the ground. How tall a tree would that take? Hint: I already
know the answer to that, and it's an impressive tree.
So dropping and flapping could have been the most common method of
OK, a pterosaur messing about on a beach sees a predator approaching. So
being unable to run rapidly, he then procedes to walk or canter to the
nearest tree (somewhat rare on beaches) while the predator is running madly
toward him. Upon reaching the tree, he tries to clamber up it in time to
evade the onrushing predator. Umh, tasty pterosaur. Why didn't he just
launch from where he was when he first noticed the predator approaching?
Within his own body length, he would be in the air and moving faster than
the predator could, and would be increasing the distance between them rather
than decreasing it.
perhaps the leaping model was employed, as the figures indicate. Some
sort of tracks will show this someday. Whether those last traces will be
feet or hands remains to be seen.
:-) If its the pes, then you've found a previously unknown pterosaur with a
totally new morphology.
One side says fingers 1-3 faced palms anterior in flight and 4
hyperextended to fold (Bennett 2008). That means the former connection
between the lateral surface of metacarpal III and the medial surface of
IV have broken because the now ventral surface of III is close to the now
ventral surface of IV
No, it just means that IV is now humongously bigger than III.
So any excess depression of manus prints vs. pedal prints is due to their
much smaller surface area, not their weight distribution. They're more
Thereby placing them in a terrestrial posture which makes a rapid takeoff
impossible. Sounds to me like Darwinian processes would do away with that
pretty quick. Tasty pterosaur.