Here (Fig. 1) is what appears to be a classic basal pterosaur foot. Long narrow metatarsals. Metatarsals 3 and 4 are the longest, as in Preondactylus and Austriadactylus (SC332466). Pedal 5.1 extends beyond metatarsal 4, as in Austriadactylus and Dimorphodon. Digit 4 is slightly longer than digit 3. Digit 5, though, appears to have an extra phalanx or two. That astragalus is oddly shaped, but everything else seems to be very pterosaurian…
Did you guess? Or did you know?
This is Tanystropheus, a close relative to the ancestors of pterosaurs. Langobardisaurus and Cosesaurus are closer to that common ancestor and to each other. And they both have this kind of foot.
Homoplasy, not Convergence
Those similar foot characters are homoplastic, not the result of convergence and attests to the antiquity of this foot morphology in the lineage of pterosaurs. Now, if we can only get the powers that be to start including Tanystropheus, Langobardisaurus, Cosesaurus (and the rest of the Fenestrasauria) with pterosaur and archosaur studies, it would be no surprise to find out where pterosaurs actually do nest in the scheme of things.
Archosaurs, as you already know, have only a vestige or less of a fifth pedal digit. This is where you start looking for the ancestors of pterosaurs.
And if you’re an archosaur-lover ~ take your blinders off.