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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.

Major problems:

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 step #3.

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.

Best regards,

David Peters