A medium-sized robust-necked azhdarchid pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Hateg Basin, Transylvania, Romania)

We describe a pterosaurian cervical vertebra collected from Maastrichtian sediments at the Pui locality in the Hateg Basin, Romania. This specimen, a medium-sized, robust fourth cervical, is distinctive in morphology and represents a new, as yet unrecognized, azhdarchid pterosaur size class within the Hateg Island fauna: it most likely belongs to a new taxon which we opt not to name here. The vertebra is referred to Azhdarchidae based on dearly preserved diagnostic features characteristic of this group and differs in proportions and anatomical details from the recently named azhdarchid Eurazhdarcho langendorfensis Vremir et al., 2013a, from the Sebes region of the Transylvanian basin. We take issue with claims that all Maastrichtian Romanian azhdarchids (and other penecontemporaneous azhdarchids and azhdarchoids) should be uncritically assumed to be synonymous: it ignores anatomical characters that allow the specimens concerned to be differentiated and is based on an erroneous "one stratum, one species" philosophy contradicted by empirical data from other azhdarchoid assemblages. It has been suggested that the absence of small to medium-sized pterosaurs in Upper Cretaceous sediments is indicative of an evolutionary trend. However, evidence from the Hateg Island fauna may indicate instead that smaller-sized pterosaurs were indeed present in this interval but remain underrepresented due to rare preservation and collection.