Scientists Discover New “Primitive Cousins of T. Rex” – Finding Sheds Light on the End of the Age of Dinosaurs in Africa

Scientists discovered fossils of two new dinosaur species in Morocco, revealing that diverse carnivorous species lived there just before the asteroid-induced extinction event 66 million years ago. Contrary to some beliefs that dinosaurs were already declining, these findings suggest they were thriving in North Africa until their abrupt end. Credit: Andrey Atuchin

Scientists in Morocco have uncovered fossils of primitive cousins of T. rex that had short, bulldog snouts and even shorter arms have been discovered by scientists in Morocco. These two newly identified dinosaur species are members of the Abelisauridae family, which were the carnivorous counterparts to the Northern Hemisphere’s tyrannosaurs. Existing during the final stages of the Cretaceous period, these discoveries underscore the rich diversity of dinosaurs in Africa right before an asteroid led to their widespread extinction 66 million years ago.

Two new species of dinosaur have been found from the end of the Cretaceous in Morocco, just outside of Casablanca. One species, found near the town of Sidi Daoui, is represented by a foot bone from a predator about two and a half meters (eight feet) long. The other, from nearby Sidi Chennane, is the shin bone of a carnivore that grew to around five meters (15 feet) in length.

Both were part of a family of primitive carnivorous dinosaurs known as abelisaurs and lived alongside the much larger abelisaur Chenanisaurus barbaricus, showing that Morocco was home to diverse dinosaur species just before a giant asteroid struck at the end of the Cretaceous, ending the age of dinosaurs.

Fossil abelisaur tibia. Credit: University of Bath

Dr Nick Longrich, from the Milner Centre for Evolution at the University of Bath, led the study. He said: “What’s surprising here is that these are marine beds.

“It’s a shallow, tropical sea full of plesiosaurs, mosasaurs, and sharks. It’s not exactly a place you’d expect to find a lot of dinosaurs. But we’re finding them.”

Even though dinosaurs account for a small proportion of the fossils, the region is so rich in fossils, it has produced the best picture of African dinosaurs from the end of the age of dinosaurs. Rather than finding the same few species, paleontologists often recover fossils from new species, suggesting the beds host an extremely diverse dinosaur fauna.

So far, the small number of dinosaur fossils that have been recovered represent five different species – a small duckbill dinosaur named Ajnabia, a long-necked titanosaur, the giant abelisaur Chenanisaurus, and now the two new abelisaurs.

Fossil abelisaur metatarsal. Credit: Nick Longrich, University of Bath

Dr Longrich said: “We have other fossils as well, but they’re currently under study. So we can’t say much about them at the moment, except that this was an amazingly diverse dinosaur fauna.”

The last dinosaurs vanished around 66 million years ago, along with as much as 90% of all species on earth, including mosasaurs, plesiosaurs, pterosaurs and ammonites. The pattern of the end-Cretaceous extinction and its causes have been debated for over two hundred years. A giant asteroid impact in the Yucatan peninsula has been linked to their demise, although it’s been argued that dinosaurs were already in decline. The Moroccan dinosaurs suggest that they thrived in North Africa up to the very end.

“The end of the Cretaceous in western North America definitely seems to become less diverse at the end,” said Longrich. “But that’s just one small part of the world. It’s not clear that you can generalize from the dinosaurs of Wyoming and Montana to the whole world.

“It also grew colder near the end, so it might not be surprising if dinosaurs at higher latitudes became less diverse. But we don’t know much about dinosaurs from lower latitudes.”

In Morocco at least, they seem to have remained diverse and successful up until the end.

“When T. rex reigned as a mega predator in North America, abelisaurs sat at the top of the food chains in North Africa,” said Nour-Eddine Jalil, a professor at the Natural History Museum and a researcher at Universite Cadi Ayyad in Morocco, who was a co-author on the paper.

“The dinosaur remains, despite their rarity, give the same messages as the more abundant marine reptile remains.

“They tell us that, just before the Cretaceous-Paleogene crisis, biodiversity was not declining but on the contrary, was diverse.”

Reference: “New fossils of Abelisauridae (Dinosauria: Theropoda) from the upper Maastrichtian of Morocco, North Africa” by Nicholas R. Longrich, Erik Isasmendi, Xabier Pereda-Suberbiola and Nour-Eddine Jalil, 22 August 2023, Cretaceous Research.
DOI: 10.1016/j.cretres.2023.105677