New toothed pterosaurs (Pterosauria: Ornithocheiridae) from the middle Cretaceous Kem Kem beds of Morocco and implications for pterosaur palaeobiogeography and diversity

Abstract

Pterodactyloid pterosaurs underwent a diversification in the Late Jurassic and Early Cretaceous, followed by a major turnover event in the mid-Cretaceous, when ornithocheirids and basal azhdarchoids were replaced by pteranodontids, nyctosaurids and azhdarchids in the latest Cretaceous. However, precise patterns of turnover are obscured by the incompleteness of the pterosaur fossil record. Fossils from the middle Cretaceous Kem Kem beds of Morocco (?Albian –Cenomanian) have helped shed light on the diversity of pterosaurs from this time and provide a window into the diversity of a continental pterosaur assemblage from this critical transitional period. Two toothed pterosaurs, the ornithocheirids Siroccopteryx moroccensis and Coloborhynchus fluviferox, have been reported from the Kem Kem beds. Here, we report a partial mandible and two premaxillae representing three additional taxa of toothed pterosaurs. The mandibular symphysis closely resembles that of Anhanguera piscator from the Romualdo Member of the Santana Formation of Brazil in the arrangement and spacing of the alveoli, the weak anterior upturn of the jaw, and the ventral crest. One premaxilla closely resembles that of the ornithocheirid Ornithocheirus simus from the Cambridge Greensand Formation of eastern England. A second premaxilla is referred to Coloborhynchus, bearing similarities to C. clavirostris from the Hastings Group of southern England, and C. fluviferox from the Kem Kem beds of Morocco. In total, the Kem Kem pterosaur fauna includes at least nine species, of which five are ornithocheirids. The Kem Kem assemblage supports the hypothesis that toothed pterosaurs remained diverse during the mid Cretaceous before disappearing from post-Cenomanian strata.