Cranial crest development in the Azhdarchoid pterosaur Tupuxuara, with a review of the genus and tapejarid monophyly

A portion of pterosaur skull from the Romualdo Member of the Santana Formation (?Albian–?Turonian, Cretaceous) of north-east Brazil provides new data on the morphology and ontogeny of azhdarchoid pterosaur cranial crests. The specimen consists of parts of the cranial bones posterodorsal to the nasoantorbital fenestra, including partial nasals, lacrimals, frontals and possibly the parietals. A posterodorsally directed premaxillary crest with a concave posterior border is located dorsal to the posterior border of the nasoantorbital fenestra. A well-defined suture indicates overlapping, posterodorsally directed growth of the premaxilla over the skull roof, suggesting that the generation of the premaxillary crest is a late ontogenetic feature and thus probably related to sexual display. The systematics of Tupuxuara and its relationship to other azhdarchoids is reviewed and a cladistic analysis of the group is presented. Tupuxuara is found to be the sister-taxon to Azhdarchidae. Tupuxuara longicristatus Kellner and Campos, 1988 is argued to be the only valid named species in this genus and Thalassodromeus Kellner and Campos, 2002 is considered a junior subjective synonym of this taxon. As originally conceived, Tapejaridae is paraphyletic: a new, more restrictive version of Tapejaridae (including Tapejara and Sinopterus dongi) might exist, but its monophyly is weakly supported. Furthermore, Tapejara was found to be paraphyletic in all trees.