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Reconstruction of the palaeoecosystem of the Upper Cretaceous (Cenomanian) Bahariya Formation of the Bahariya Oasis, Western Desert of Egypt, showing diversity of large-bodied theropod dinosaurs. in Salem, Lamanna, O'Connor, ... et Sallam, 2022. DOI: 10.1098/rsos.220106 Artwork by Andrew McAfee, Carnegie Museum of Natural History. |
Abstract
Numerous non-avian theropod dinosaur fossils have been reported from the Upper Cretaceous (Cenomanian) Bahariya Formation, Bahariya Oasis, Western Desert of Egypt, but unambiguous materials of Abelisauridae have yet to be documented. Here we report Mansoura University Vertebrate Paleontology Center (MUVP) specimen 477, an isolated, well-preserved tenth cervical vertebra of a medium-sized abelisaurid from the Bahariya Formation. The new vertebra shows affinities with those of other Upper Cretaceous abelisaurids from Madagascar and South America, such as Majungasaurus crenatissimus, Carnotaurus sastrei, Viavenator exxoni and a generically indeterminate Patagonian specimen (Museo Padre Molina specimen 99). Phylogenetic analysis recovers the Bahariya form within Abelisauridae, either in a polytomy of all included abelisaurids (strict consensus tree) or as an early branching member of the otherwise South American clade Brachyrostra (50% majority rule consensus tree). MUVP 477, therefore, represents the first confirmed abelisaurid fossil from the Bahariya Formation and the oldest definitive record of the clade from Egypt and northeastern Africa more generally. The new vertebra demonstrates the wide geographical distribution of Abelisauridae across North Africa during the middle Cretaceous and augments the already extraordinarily diverse large-bodied theropod assemblage of the Bahariya Formation, a record that also includes representatives of Spinosauridae, Carcharodontosauridae and Bahariasauridae.
Keywords: Abelisauridae, Egypt, Africa, Cretaceous, Bahariya Formation
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| Tenth cervical vertebra of Abelisauridae indet. (MUVP 477) in cranial (a), caudal (b), left lateral (c), right dorsolateral (d), ventral (e) and dorsal (f) views. |
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| Reconstruction of the palaeoecosystem of the Upper Cretaceous (Cenomanian) Bahariya Formation of the Bahariya Oasis, Western Desert of Egypt, showing diversity of large-bodied theropod dinosaurs. In the foreground, the unidentified abelisaurid described herein (right) confronts the spinosaurid Spinosaurus aegyptiacus (left centre, with dipnoan (lungfish) Retodus tuberculatus in jaws) and the carcharodontosaurid Carcharodontosaurus saharicus (right centre) while two individuals of the stomatosuchid crocodyliform Stomatosuchus inermis (left) look on. In the background, a herd of the titanosaurian sauropod Paralititan stromeri (left) warily regards these theropods and two individuals of the bahariasaurid Bahariasaurus ingens (far right) while a small flock of an undescribed pterosaur soars above. The vegetation is dominated by the mangrove-like tree fern Weichselia reticulata. Artwork by Andrew McAfee, Carnegie Museum of Natural History. |
Conclusion:
The cervical vertebra (MUVP 477) described herein represents the first confirmed fossil of Abelisauridae from the Bahariya Formation, establishing it as the oldest definitive record of this theropod clade from Egypt and northeastern Africa more generally. The new vertebra demonstrates the wide geographical distribution of abelisaurids across North Africa during the middle Cretaceous and augments the already extraordinarily diverse large-bodied non-avian theropod record of the Bahariya Formation, a unit that also preserves representatives of Spinosauridae, Carcharodontosauridae and Bahariasauridae. This abelisaurid/spinosaurid/carcharodontosaurid/bahariasaurid faunal assemblage appears to have extended across most or all of northern Africa during the Cenomanian, suggesting that the Trans-Saharan Seaway did not represent a significant barrier to large-bodied theropod dispersal at this time. The Bahariya Formation holds unrealized potential to improve understanding of this northern African Cenomanian fauna due to the relative commonality of phylogenetically informative associated partial skeletons in this stratigraphic unit.
Belal S. Salem, Matthew C. Lamanna, Patrick M. O'Connor, Gamal M. El-Qot, Fatma Shaker, Wael A. Thabet, Sanaa El-Sayed and Hesham M. Sallam. 2022. First Definitive Record of Abelisauridae (Theropoda: Ceratosauria) from the Cretaceous Bahariya Formation, Bahariya Oasis, Western Desert of Egypt. R. Soc. open sci. 9220106. DOI: 10.1098/rsos.220106
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