The relationships of Cuspicephalus scarfi Martill and Etches, 2013 and Normannognathus wellnhoferi Buffetaut et al., 1998 to other monofenestratan pterosaurs

The evolution of pterodactyloid pterosaurs occurred in a ‘modular’ fashion with ‘pterodactyloid’-type crania and cervical vertebrae evolving in pterodactyloid sister taxa – early monofenestratan pterosaurs – before later postcervical modifications marked the development of the true pterodactyloid condition. This means of evolution creates problems for distinguishing isolated pterodactyloid crania from those of non-pterodactyloid monofenestratans, and has led to uncertainty over the affinities of two Late Jurassic European pterosaurs known only from skulls, Cuspicephalus scarfi Martill and Etches, 2013 and Normannognathus wellnhoferi Buffetaut et al., 1998. Some aspects of their cranial anatomy suggest affinities to early pterodactyloids – specifically the Germanodactylidae – while others indicate a relationship with a group of non-pterodactyloid monofenestratans, the Wukongopteridae. Here, we characterise the skulls of Jurassic monofenestratans to provide greater insight into the identity of these pterosaurs. We find a suite of characters indicating that Cuspicephalus is a wukongopterid, notable for being a particularly large and long snouted member of the group, as well as the youngest, and the first European record of this clade. The affinities of Normannognathus are less clear however. We consider its previous allocation to the Germanodactylidae doubtful, and note some similarities it shares with ctenochasmatoid pterodactyloids, but the only known specimen is probably too fragmentary for confident referral to any specific clade within Monofenestrata.