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First definitive record of Abelisauridae (Theropoda: Ceratosauria) from the Cretaceous Bahariya Formation, Bahariya Oasis, Western Desert of Egypt - PubMed

  • ️Sat Jan 01 2022

First definitive record of Abelisauridae (Theropoda: Ceratosauria) from the Cretaceous Bahariya Formation, Bahariya Oasis, Western Desert of Egypt

Belal S Salem et al. R Soc Open Sci. 2022.

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; Africa; Bahariya Formation; Cretaceous; Egypt.

© 2022 The Authors.

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Conflict of interest statement

We declare we have no competing interests.

Figures

Figure 1.
Figure 1.

Location of the fossil locality. (a) Map of Egypt showing location of the Bahariya Oasis, Western Desert of Egypt (green). (b) Site (indicated by star) that produced the abelisaurid vertebra (MUVP 477) described herein, in the Gebel El Dist region of the Bahariya Oasis.

Figure 2.
Figure 2.

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. cacdl, caudal centrodiapophyseal lamina; cdf, centrodiapophyseal fossa; cpof, centropostzygapophyseal fossa; cpol, centropostzygapophyseal lamina; cprf, centroprezygapophyseal fossa; cprl, centroprezygapophyseal lamina; crcdl, cranial centrodiapophyseal lamina; dp, diapophysis; ep, epipophysis; isls, interspinous ligament scar; nc, neural canal; ns, neural spine; pfr, pneumatic foramen; pl, pleurocoel; pocdf, postzygapophyseal centrodiapophyseal fossa; podl, postzygodiapophyseal lamina; poz, postzygapophysis; pp, parapophysis; prcdf, prezygapophyseal centrodiapophyseal fossa; prdl, prezygodiapophyseal lamina; prz, prezygapophysis; spof, spinopostzygapophyseal fossa; sprf, spinoprezygapophyseal fossa; tpol, intrapostzygapophyseal lamina; tprl, intraprezygapophyseal lamina.

Figure 3.
Figure 3.

Tenth cervical vertebra of representative abelisaurids in cranial (a,c,e,g,i) and left lateral (b,d,f,h,j) views. (a,b) Abelisauridae indet. (MUVP 477) from Egypt. (c,d) Majungasaurus crenatissimus (UA 8678) after [27]. (e,f) Carnotaurus sastrei (MACN-CH 894) after [26]. (g,h) Viavenator exxoni (MAU-Pv-LI-530) after [28,30]. (i,j) Abelisauridae indet. from Argentina (MPM-99) after [31]. Cranial views (a,c,e,g,i) scaled to same transverse width to facilitate comparisons. Dashed lines in (a,c,i,j) represent reconstructed areas.

Figure 4.
Figure 4.

Phylogenetic position of Abelisauridae indet. (MUVP 477). Strict (a) and 50% majority rule (b) consensus trees of 1640 most parsimonious trees (MPTs) of 758 steps recovered by parsimony analysis (Tree analysis using New Technology v. 1.1 [46]) of the data matrix presented by Smyth et al. [41] with the addition of MUVP 477. Node names mostly follow Tortosa et al. [3] and Smyth et al. [41]; numerals in (b) are percentages of MPTs. Note that several recent works have regarded Camarillasaurus cirugedae and Deltadromeus agilis as members of Tetanurae rather than Ceratosauria; specifically, Samathi et al. [47] reappraised Camarillasaurus as a representative of Spinosauridae, and Apesteguía et al. [48] and Motta et al. [49] regarded Deltadromeus as a member of Bahariasauridae, a clade with potential affinities to Megaraptora. As such, we regard the phylogenetic positions of these two forms depicted above with caution. All ceratosaur silhouettes from PhyloPic (

http://phylopic.org/

); individual credits as follows: Ceratosauria (FunkMonk); Abelisauroidea (Iain Reid); Noasauridae, Majungasaurinae and Furileusauria (Scott Hartman); Abelisauria (Andrew Farke and Joseph Sertich); Abelisauridae and Brachyrostra (Jagged Fang Designs).

Figure 5.
Figure 5.

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.

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