Newly discovered, primitive cousins of T. rex shed light on the end of the age of dinosaurs in Africa

Scientists in Morocco have found fossils of early relatives of Tyrannosaurus rex that had even shorter limbs and small, bulldog-like snouts. The two newly discovered dinosaur species are members of the Abelisauridae family, which included predatory dinosaurs that served as the Northern Hemisphere's equivalent of tyrannosaurs. They demonstrate that dinosaur diversity existed in Africa shortly before the wholesale extinction of these animals by an asteroid 66 million years ago. They lived at the end of the Cretaceous period.

In Morocco, not far from Casablanca, two new species of dinosaurs from the end of the Cretaceous period have been discovered. One species is represented by a foot bone from a predator that was around 2.5 meters (eight feet) long and was discovered close to the village of Sidi Daoui. The other comes from the adjacent Sidi Chennane and is the shin bone of a carnivore that reached a maximum length of fifteen feet, or five meters.

The fact that both belonged to the same family of primitive carnivorous dinosaurs, known as abelisaurs, and coexisted with the larger abelisaur Chenanisaurus barbaricus indicates that Morocco was home to a variety of dinosaur species right up until the end of the Cretaceous period, when a massive asteroid struck and ended the dinosaur era.

The study's lead author, Dr. Nick Longrich of the University of Bath's Milner Center for Evolution, had it published in Cretaceous Research. "The fact that these are marine beds is surprising," he remarked. There are sharks, mosasaurs, and plesiosaurs in this shallow tropical water. You wouldn't exactly expect to discover a lot of dinosaurs there. Still, we're locating them."

The area is so rich in fossils that it has generated the greatest image of African dinosaurs from the end of the dinosaur era, despite the fact that dinosaurs make up a very tiny percentage of the fossils.

Paleontologists frequently uncover fossils from new species rather than the same few species, indicating that the beds support a very diversified dinosaur fauna.

Five distinct species are represented by the few dinosaur remains that have been found thus far: the huge abelisaur Chenanisaurus, the long-necked titanosaur Ajnabia, the little duckbill dinosaur, and now the two new abelisaurs.

"We have other fossils as well, but they're currently under study," Dr. Longrich stated. Thus, the only thing we can tell about them at this time is that the dinosaur fauna was incredibly varied."

About 66 million years ago, the last dinosaurs and up to 90% of all species on Earth—including mosasaurs, plesiosaurs, pterosaurs, and ammonites—went extinct. Over two centuries have passed since the pattern of the end-Cretaceous extinction and its causes were discussed.

Although it has been suggested that dinosaurs were already in decline, their extinction has been connected to a massive asteroid impact near the Yucatan peninsula. The dinosaurs from Morocco imply that they survived and perhaps prospered in North Africa.

"There's a noticeable decrease in diversity towards the end of the Cretaceous in western North America," observed Longrich. However, that is but a tiny portion of the globe. It's unclear if global generalizations about dinosaurs can be drawn from specimens found in Wyoming and Montana.

Furthermore, the temperature dropped at the end, thus it may not be shocking if the diversity of dinosaurs at higher latitudes decreased. However, nothing is known about dinosaurs that lived at lower latitudes."

They appear to have continued to be profitable and diversified until the very end, at least in Morocco.

A professor at the Natural History Museum and researcher at Universite Cadi Ayyad in Morocco, Nour-Eddine Jalil was a co-author of the work. "When T. rex reigned as a megapredator in North America, abelisaurs sat at the top of the food chains in North Africa," wrote Jalil.

"Even though they are rare, dinosaur bones convey the same information as marine reptile remnants, which are more common.

"They inform us that biodiversity was not decreasing but rather varied just prior to the Cretaceous-Paleogene crisis."

Provided by University of Bath