The Heretical View
One basal pterosaur, MPUM 6009 (Wild 1978), was an obligate biped, retaining the long-legged morphology of its ancestral sisters, Sharovipteryx and Longisquama. All pterosaurs following MPUM 6009 (such as Raeticodactylus and Eudimorphodon) had shorter hind limbs and longer forelimbs, a combination that enabled quadrupedal locomotion.
MPUM 6009 was considered a small Carniadactylus by Dalla Vecchia (2009), but the differences are many.
Longer Legs, Shorter Forelimbs
Here the reconstruction tells the tale. Question is, is the reconstruction accurate? The clues are, admittedly ephemeral, yet even without such long legs, MPUM 6009 nests at the base of the Pterosauria. So long legs are not beyond the realm of possibility. The relatively short neck allies this basal pterosaur with Longisquama, the outgroup sister taxon. The laterally increasing toe length and deep pelvis also ally this taxon with Longisquama. The sternal complex is also essentially identical.
Such long legs and short forelimbs “ally” this pterosaur with Scleromochlus, and basal dinosaurs, but — really, seriously — hardly at all. It’s convergence!! So if anyone from the traditional camp wants to bitch about this reconstruction, think twice. You’ll only be shooting yourself in the foot. Things happen when the forelimbs are elevated off the substrate, as we humans all can attest.
How Living Lizards Run Bipedally
The Bruce Jayne Lab in Cincinnati, Ohio, has produced a video of a zebra-tailed lizard (Callisaurus) in fast quadrupedal and bipedal locomotion filmed on a treadmill. When the fore limbs are elevated the hind limbs go digitigrade. The speed is an incredible 11 meters per second.
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.
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.)rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.