The Royal Museum Lecture Series for 2012 featured as one of its speakers, Dr. Mike Habib of Chatham University and placed both the video and audio on YouTube. You can see it for yourself here. Dr. Habib is a good speaker, very entertaining, informative and knowledgeable. He is famous for his skeletal strength studies using beam analysis. This led Habib to his famous forelimb leap launch hypothesis. I blogged earlier on the seven problems found with that hypothesis, including falsifying the data on the hands of its subject matter, the pterosaur Anhanguera.
Habib reports all pterosaurs were quadrupedal, ignoring two reports (Peters 2011, Kim et al. (2012) on bipedal pterosaurs.
On the positive side, Habib compared the humerus and femur cross sections of a small owl with the humerus of an azhdarchid pterosaur, only a few millimeters thick (which is why it is nearly impossible to age such pterosaurs because the earlier layers are resorbed and disappear). He noted higher strength in the humerus compared to birds and less strength in the hind limb, the opposite of birds. Habib reported take-off is hind-limb driven in birds, with the majority of the launch forces coming from the hind limbs, even in tiny-footed hummingbirds where it is reduced to 50/50. The opposite is the case with most pterosaurs, according to Habib, with the forelimbs providing the initial takeoff push.
Habib reports you don’t get a lot of lift initially, which is why the hindlimbs are so important during takeoff in birds, bringing to mind a swimming competition and using the feet to kick off the wall. A vampire bat, by contrast, uses a forelimb launch to bound off the ground with plenty of time to unfold the wings and start the initial flap. This is the analog to pterosaur forelimb take-off, according to Habib.
Wing loading determines airspeed for launching. After feeding a vampire bat has wing loading similar to a larger bird or bat, Habib reported.
Using Quetzalcoatlus Habib calculated a 14.7 m/second launch velocity with a launch time of 0.59 seconds. He reports the flight motor is also the launch motor in pterosaurs, which is the reason why certain pterosaurs were able to become so much larger than birds. This is also why the forelimbs were so much stronger than the hind limbs in azhdarchids, according to Habib.
Habib considered birds, not pterosaurs, to be divers and seed eaters. Both were arboreal predators. Only pterosaurs were hawkers and soaring giants. Habib does not note the similar sizes found in ornithocheirids, pelicans and albatrosses seen here.
Habib reported a 10,000 mile flight range non-stop for Quetzalcoatlus, similar to that of the much smaller Arctic common tern. Habib reports the earlier, smaller pterosaurs could have launched quadrupedally or bipedally. The question and answer period introduced some interesting subjects.
Taking off from water was blogged earlier.
What started a quadrupedal launch?
It’s [mathematically] better at overperformance during launch, reports Habib, but such a launch puts on additional constraints. Habib reported, since the membrane was attached to the lower leg that helps. He reports if bipedal with a broad wing membrane attached to the lower leg, you get an inappropriate angle of attack (too steep) and flutter in the trailing edge of the wing. Of course, this again ignores all the evidence for a narrow chord membrane and no evidence whatsoever for a deep chord.
Habib thought pterosaurs used anaerobic muscles to fly with. Such muscles provide more burst activity, but tire quickly. Aerobic muscles tend to sustain activity longer, oxygenated by a constant stream of respiration.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Habib M 2012. Royal Tyrrell lecture series.
Kim JY, Lockley MG, Kim KS, Seo SJ and Lim JD 2012. Enigmatic Giant Pterosaur Tracks and Associated Ichnofauna from the Cretaceous of Korea: Implication for the Bipedal Locomotion of Pterosaurs. Ichnos 19 (1-2): 50-65.DOI:10.1080/10420940.2011.625779 online
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605