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Pterosaur take-off movie on the NG site
This is a great explanation, movie and illustration. Great pteroid
placement. Finally I understand Mike Habib's thinking. At last I see
where the magic took place and the science left the room, even if
inadvertent and with the best of possible intentions.
Minor problems (Tupuxuara painting):
1. When quadrupedal, the palms would be in the neutral position,
neither suppinated nor pronated, but positioned as in clapping or tree
grappling. When pressed against the ground then, the fingers splay
laterally to posterolaterally. The painting of Tupuxuara has trouble
with putting the fingers "pads and claw tips down."
2. Chest is way too shallow on painting, should be 3x neck depth.
Upper arms way too gracile. Beef them up!
3. Should be a shallow keel on the dentary for Tupuxuara.
4. No hair?? Too little hair? Needs more fuzz.
5. Wings should nearly disappear whenever folded. Wings don't extend
onto the tibia, but are stretched between the elbow and wingtip with a
fuselage fillet extending back toward the femur. No fossil shows it
any other way.
Minor problems (Anhanguera movie):
1. Ordinarily on the ground, the knees are flexed at 90 degrees,
extending only during leaps and in flight. Move feet beneath the
torso. This happens when you bend the knees. Footprints show
pterosaurs are not wide-splayed like this. (We don't have Anhanguera
tracks, but we do have beachcombing pterosaur tracks). When the knees
are bent the feet move further forward, beneath the center of balance
near the shoulder joint.
2. Needs prepubic bones. I know, they're unknown in Anhanuera, but all
other pterosaurs have them.
3. Anhanguera feet are much smaller than you show. The smallest feet
of all pterosaurs. During the leap, the feet should elevate from heel
to toe in sequence, delivering a final push with the tips of the toes.
4. The forelimbs are quite wide. A more efficient vector would have
the limbs directly beneath the shoulders.
5. Anhanguera did not have a typical tetrapod gait, nor a typical
pterosaur gait. With such short legs, the force vectors from fingers
to shoulder could never point forward. This relegates Anhanguera to a
weak bipedal hindlimb propulsion (knees bent) with support, not
propulsion, coming from the wings. Like using crutches, except the
crutch tips have to stay in front of the shoulder the whole time on
Anhanguera. My guess is it stayed airborne as much as possible.
1. The narrator reports the "knuckles of the wing fingers rest upon
the ground", but this is not so according to tracks. Only would be so
in the case of Nyctosaurus (and pterosaurs like it), which has
vestiges for fingers and a much longer metacarpal.
2. On the closeup view of the slipping tendon, metacarpals I-III are
inaccurately shortened. In reality they should extend as far as the
big wing metacarpal (#4). If this was done for illustrative purposes,
then it cheated the whole concept. Fingers 1-3 should be larger (1/3
of the metacarpal length in Anhanguera) with much deeper unguals (claw
bones), further lengthened by keratinous extensions. Ordinarily, and
pterosaur tracks show this, these three fingers take ALL of the weight
not taken by the hind limbs. There is no deep track preservation of
digit IV. There is no trace at all, typically, of digit IV. If no
weight is placed on this joint, then there is no elastic recoil and
the hypothesis has no power source for takeoff.
3. Whenever an animal leaps into the air (think of frogs, kangaroos
and basketball players), after the leap the legs extend straight back
trailing the rest of the body in the line of the trajectory until they
draw up somewhat and extend forward near the apex to prepare for a
springy landing, lined up with the anticipated landing spot. In this
pterosaur animation "the elastic recoil forcefully extends the
forelimbs," but the wing finger is not forcefully extended. The
animator holds it back, to avoid contact with the ground, which would
have been inevitable if indeed there was an elastic recoil at this
joint. But slamming the wing finger into the ground won't work...
4. So the elbow is forcefully hyper-extended and no distal (ground
contact) elements are forcefully extended. When the elbow is
hyperextended the propatagium is minimized as it is stretched to its
limit. Birds have a ligament to prevent exactly this sort of
hyperextension of the elbow. Bats do too.
The 1-4 sequence of an azhdarchid takeoff called "Winging it":
1. This sequence shows that all of the propulsion comes from the elbow
joint because the wing finger is not fully extended immediately after
take-off (according to the illustration), as it would have to be if
indeed a recoil of this joint is operating. Here there's not enough
coil in step #1, not enough recoil in step #2 (note the pterosaur is
no higher after extension) and for some reason it keeps on rising in
Mike, sorry I didn't nail these problems earlier. I never realized you
had shorted the fingers and metacarpals I-III to make the recoil
pressure on the big metacarpal possible.