Rhabdodontid (Dinosauria, Ornithopoda) diversity suggested by the first documented occurrence of associated cranial and postcranial material at Vălioara (uppermost Cretaceous Densuș-Ciula Formation, Hațeg Basin, Romania)

Abstract

Associated and partly articulated cranial and postcranial elements of rhabdodontid ornithopod dinosaurs recovered from the recently rediscovered Maastrichtian (Upper Cretaceous) vertebrate site K2 near Vălioara in the westernmost part of the Hațeg Basin (Transylvania, Romania) are described in detail. These elements come from a multitaxic bonebed discovered in the continental deposits of the Densuș-Ciula Formation, and originate from at least two individuals, although available evidence suggests that these individuals belong to a single taxon. This taxon shares most similarities with specimens referred to Zalmoxes shqiperorum in earlier publications; however, certain skeletal elements also bear characteristics that are reminiscent of Z. robustus, the other Zalmoxes species. Furthermore, the new K2 material also exhibits features that differ from both known Zalmoxes species, as well as from the recently described third Transylvanian rhabdodontid, Transylvanosaurus. Accordingly, given that it appears to be distinct from other previously known Transylvanian rhabdodontids, the taxon represented by this material is here only referred to as Rhabdodontidae indet. A comprehensive phylogenetic analysis recovered the ‘K2 rhabdodontid’ within Rhabdodontidae, although the in-group relationships of this clade remain poorly resolved. The new observations presented here indicate that this European endemic basal iguanodontian group was more diverse (at intra- and/or interspecific level) in the Transylvanian area than previously thought, while also emphasize the necessity of the revision and proper re-diagnosis of the currently known Transylvanian rhabdodontid material that was previously assigned to Zalmoxes.