On Late Cretaceous toothless pterosaurs

Inabtanin skeletal by SlvrHwk.

The pterosaur fossil reccord is rather patchy considering their hollow bones do not preserve well. So, given the Late Cretaceous has few sites with exceptional preservation, we had to make due with fragmentary evidence. Most temrinal Cretaceous fossils belonged to Azhdarchidae, so it previously assumed they were the only pterosaurs around. Then other pterosaur groups like pteranodontians and non-azhdarchid azhdarchoids (as well as oddballs like Piksi and Navajodactylus) showed up, and now we understand that the last pterosaur faunas were incredibly diverse.

But there seems to have been a moving of goalposts, because now people claim only toothless pterosaurs were present in the Late Cretaceous.

I’m pretty convinced this is again an artifact of the fossil reccord, that toothed pterosaurs will eventually turn up, especially since toothed pterosaurs did survive the Cenomanian/Turonian extinction event (i.e. Ferrodraco) and the aforementioned oddballs. But the prevalence of azhdarchoid and pteranodontian taxa does seem to suggest that toothless pterosaurs were at least dominant, so this alone can’t be justified as merely an artifact of preservation. Toothed pteranodontians, after all, are ubiquitous in the Early Cretaceous, so their sudden disappearence and replacement by pteranodontids and nyctosaurs is rather suspicious.

Why, therefore, did toothless pterosaurs rise?

It’s possible that, like with birds, toothlessness helped broaden the diet of pterosaurs, making toothless taxa have an edge during the environmental trials of the Cenomanian/Turonian extinction. This might ring true for azhdarchoids, which include generalists, but this argument falls apart when taking into consideration pteranodontians, which are mostly specialised marine animals (unless juvenile pteranodontids were foraging on land).

Ultimately, I think this is an artifact of preservation, and it’s just a matter of time until toothed pterosaurs show up in the Campanian and Maastrichtian. It reminds me of the situation with enantiornitheans, similarly once thought to only have toothless taxa at the end of the Cretaceous.