The first thing you notice is
Raeticodactlylus (Fig. 1) is twice as tall as MPUM 6009. You might also notice that the humerus and antebrachium are relatively longer and the hind limbs are relatively shorter in Raeticodactylus. The third thing you might notice is the humerus and antebrachium are no thicker in Raeticodactylus than in the half-sized MPUM 6009. This makes Raeticodactylus the most gracile and fragile pterosaur of all time. Essentially Raeticodactylus was a pterosaurian box kite.
Raeticodactylus is also the first pterosaur capable of touching its hands to the substrate while walking upright. All other pterosaurs follow this pattern. It also had a longer neck, more than twice as long as in MPUM 6009.
The Raeticodactylus horn/crest deserves some attention
because it looks like it had a precursor in soft tissue in MPUM 6009 (Fig. 2). Th rostral crest also has a homolog in Austriadactylus (Fig. 3).
Raeticodactylus also had a dentary keel/crest (Fig. 1). And the best explanation I can come up with for the elongate articular at the rear of the jaw is for another sort of decoration by itself or as a post to hoist or open a throat decoration.
Another skinny pterosaur
The skull of Austriadactylus might make it look tough, but like its sister, Raeticodactylus, it was just another hyper-gracile Triassic pterosaur. Even so, the caudals were more robust than in MPUM 6009, so something was happening there, at least as a counterbalance while bipedal.
Evidently greater size was important for Triassic pterosaurs. Greater strength, not so much.
So this brings up forelimb launch.
In MPUM 6009, why would you give up using those nice long hind limbs to bend so low for a forelimb launch? It doesn’t make sense here.
In Raeticodactylus and Austriadactylus the fore limbs were longer, the hind limbs were shorter, but still, there is not great strength in those soda-straw-like bones. With larger skinnier wings, it appears as though these two were trying to maximize the lift/weight ratio. The forelimb launch has its problems, discussed here and here.
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.
Stecher R 2008. A new Triassic pterosaur from Switzerland (Central Austroalpine, Grisons),Raeticodactylus filisurensis gen. et sp. nov.”. Swiss Journal of Geosciences 101: 185. doi:10.1007/s00015-008-1252-6. Online First
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.