A maker of Rhamphichnus footprints by Mark Witton. Note pronated arms.
There are three main pterosaur ichnotaxa (footprints assigned taxonomically):
- Pteraichnus is by far the most common, occuring from the Jurassic to the very end of the Cretaceous, and can be considered a bit of a wastebasket taxon, though it’s well distinguished by lateral three-fingered foreprints and large hindprints.
- Haenamichnus are Maastrichtian tracks assigned specifically to azhdarchids. These are very large in size and differ from Pteraichnus by having more compact footprints, with digits barely differentiated.
- Rhamphichnus are tracks made by non-pterodactyloid pterosaurs. They differ from the rest in having pronated forelimbs and more square-shaped hindprints with longer toes.
These foot prints offer quite a lot about pterosaur palaeobiology. Haenamichnus validates the notion that azhdarchids had compact feet and were specialised to hunt in terrestrial environments, while Rhamphichnus shows that early pterosaurs could rotate their forelimbs like mammals can. But the ones I find most interesting are the ‘generic’ Pteraichnus. While as mentioned above they might be a bit of a wastebasket, they are typically assumed to be made by ctenochasmatoids or dsungaripteroids (Witton 2013). Since they last until the end of the Cretaceous, this could indicate the presence of these pterosaurs well past the end of their fossils.
This has precedent, as Pteraichnus attributed to dsungaripteroids have been found in Late Cretaceous deposits, tens of millions of years after the closest footprint makers disappear from the fossil reccord. Therefore, they indicate long fossil ghost lineages.
Hopefully, more studies will be conducted on pterosaur footprints.