Dr Mike Habib
gave a one-hour talk on pterosaurs and his hypothesis of forelimb takeoff back in 2012 when the idea was novel.. That talk was uploaded to YouTube here. In counterpoint back then we discussed Habib’s forelimb launch hypothesis for pterosaurs here and here. We’ll continue with that discussion today.
that he does not believe or is not aware of flightless pterosaurs, but I think he was aware of Jme-Sos 2028, which was in ReptileEvolution in 2011 and entered the literature in 2013. Habib does not believe in bipedal pterosaurs, despite bipedal tracks. He notes a tendency to produce giant flyers, but actually they quite rare with regard to taxon number, and were only present in the latest Cretaceous. Habib does not recognize tiny pterosaurs as adults and he does not believe in multi-modality (walking disconnected from flying), despite fossil evidence for disconnected hind and forelimbs. Habib did not discuss pterosaur origins.
for figuring out the inner and outer diameter of long pterosaur bones. The bone is thinner than in birds, about the proportions of a cardboard paper tube. Key to Habib’s hypothesis, he notes the forelimbs are stronger than the hind limbs in pterosaurs. He notes the hind limbs of pterosaurs are average-to-weak compared to birds. Furthermore, Habib reports that take-off in birds is ‘hindlimb’ driven with takeoff initiated 80-90% by leaping, the rest with a downbeat. Even in hummingbirds with their tiny legs and feet the ratio is 50-50.
They could balance with their feet beneath their armpits, like birds do. Quadrupedal ptero tracks were all produced by a few clades of beachcombing pterosaurs during their browsing mode. All of these had relatively small wing claws. Other pterosaurs had much larger trenchant manual claws, ill-suited for contact with the ground.
all of the animated pterosaurs that Dr. Habib approved appear to be helium filled as the first down flap comes a long time after the initial launch. Moreover, none of the animations show the pterosaur leaping several times its standing height, as in the vampire bat. Worse yet, the giant wing fingers, which initially are folded posteriorly during the forelimb leap need to be extended prior to or at the acme of the leap, but initially there is no airspace to do this. Based on the orientation of the ventral orientation of the forelimbs during launch and recoil, the wing finger has to extend ventrally in the plane of the wing, This is hazardous to the swinging wing tip if it contacts the launch pad. The ground gets in the way unless the pterosaur is high enough to avoid this. All pterosaur takeoff animations authorized by Dr. Habib appear to glaze over this point, as if the long wing finger had no mass or moment arm and the initial leap never experiences recoil in the ventral plane. Rather the wings imeediately pop out effortlessly. Even a lightweight fishing rod takes a little time and effort to get from one point to another. As a suitable analog, imagine doing a leaping pushup high enough to extend and produce a downflap with fishing rods rotating ventrally in both hands. Much better to flap and run from the start for maximum ground speed and thrust.
cannot initially leap its own height, or more, from a standing start, it seems unikely that a larger pterosaur can do this in the manner of tiny vampire bats. Size matters.