Paleontologists have unearthed a well-preserved cervical vertebra of a medium-sized abelisaurid ceratosaur in the Bahariya Oasis of the Western Desert of Egypt. It represents the first confirmed abelisaurid fossil from the Bahariya Formation and the oldest definitive record of abelisaurids from Egypt and northeastern Africa more generally.

Reconstruction of the paleoecosystem of the Upper Cretaceous 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 center, with the lungfish Retodus tuberculatus in jaws) and the carcharodontosaurid Carcharodontosaurus saharicus (right center) 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. Image credit: Andrew McAfee, Carnegie Museum of Natural History.

Abelisaurid ceratosaurs were among the most diverse and geographically widespread medium- to large-bodied theropod dinosaurs during the Cretaceous period in the southern landmasses.

They occupied carnivorous niches in South America, continental Africa, Indo-Madagascar, Europe and possibly Australia.

Nevertheless, despite the rich and ever-increasing non-avian dinosaur record of Egypt, only highly fragmentary evidence of abelisaurids came to light from this nation and northeastern Africa in general.

The new fossil — a well-preserved vertebra from the base of the neck — was recovered in 2016 from the Bahariya Formation in Egypt.

The individual dinosaur the specimen belonged to lived approximately 98 million years ago (Upper Cretaceous epoch).

It likely had a bulldog-like face, small teeth, tiny arms, and was 6 m (20 feet) in length.

“During the mid-Cretaceous, the Bahariya Oasis would’ve been one of the most terrifying places on the planet,” said Belal Salem, a graduate student at Ohio University.

“How all these huge predators managed to coexist remains a mystery, though it’s probably related to their having eaten different things, their having adapted to hunt different prey.”

The new abelisaurid vertebra holds implications for the biodiversity of Cretaceous dinosaurs in Egypt and the entire northern region of Africa.

It is the oldest known abelisaurid fossil from northeastern Africa, and shows that, during the mid-Cretaceous, these dinosaurs ranged across much of the northern part of the continent, east to west from present day Egypt to Morocco, to as far south as Niger and potentially beyond.

“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,” the paleontologists said.

“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.”

Source: sci.news