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T. rex cousins had even shorter arms and bulldog snouts

An unexpected discovery in Morocco has brought to light fossils of two previously unknown dinosaur species, offering a better understanding of the prehistoric period leading up to the cataclysmic asteroid impact 66 million years ago. 

These creatures, referred to as “primitive cousins of T rex,” provide crucial insights into the age of dinosaurs, particularly in Africa. Fossil analyses revealed that these dinosaurs had short, bulldog snouts and even shorter arms than T. rex.

The Abelisauridae family

Scientists uncovered the fossils near Casablanca, in the vicinity of Sidi Daoui and Sidi Chennane. The first of these dinosaurs, deduced from a foot bone, suggests a predator approximately eight feet in length. The latter, determined by a shin bone, indicates a carnivore that reached around 15 feet.

What makes these species particularly noteworthy is their affiliation to the Abelisauridae family, a group of carnivorous dinosaurs that rivaled the famous tyrannosaurs of the Northern Hemisphere. 

New insights into African dinosaurs

Furthermore, the new species coexisted with the significantly larger abelisaur Chenanisaurus barbaricus. This coexistence underlines Morocco’s biodiversity in the age leading up to the catastrophic asteroid impact that brought about the end of the Cretaceous period and the subsequent demise of the dinosaurs.

The man leading this discovery, Dr. Nick Longrich of the Milner Centre for Evolution at the University of Bath, expressed surprise at the location of the finds.

“What’s surprising here is that these are marine beds,” said Dr. Longrich. “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.”

Despite dinosaurs making up only a small fraction of its fossil record, the region paints a comprehensive picture of African dinosaurs at the end of their era. 

Amazing dinosaur diversity

In addition to the newly discovered abelisaurs, there are records of Ajnabia, a small duckbill dinosaur, a long-necked titanosaur, and the gargantuan abelisaur Chenanisaurus.

This area, rich with fossils, continually surprises researchers with the diversity of its specimens. 

“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,” said Dr. Longrich.

Discovery challenges extinction theories 

The extinction event that led to the loss of about 90% of earth’s species, including the dinosaurs, plesiosaurs, mosasaurs, pterosaurs, and ammonites, has long been the subject of academic debate. 

The Moroccan discoveries challenge the notion that dinosaurs were waning before the asteroid struck.

“The end of the Cretaceous in western North America definitely seems to become less diverse at the end,” said Dr. 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.”

Study implications 

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

“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.”

More about T. rex

Tyrannosaurus rex, often referred to as T. rex, is one of the most iconic and well-recognized dinosaurs in the world. 


T. rex was a bipedal carnivore with a massive skull and large, powerful jaws filled with sharp teeth. Some of its teeth could be up to 9 inches long. 

T. rex had strong hind limbs, tiny front limbs with two fingers each, and a long, heavy tail, which provided balance and allowed it to move quickly.


Adult T. rexes could grow up to 40 feet (12 meters) in length, 20 feet (6 meters) in height, and weigh around 9 tons.

Habitat and range

Fossils of T. rex have been primarily found in North America, in rock formations dating to the Late Cretaceous Period, around 68-66 million years ago.


As a carnivore, T. rex primarily fed on herbivorous dinosaurs, including hadrosaurs and ceratopsians. There’s evidence to suggest they might have been scavengers as well, but this is a topic of debate among paleontologists.


T. rex had forward-facing eyes, granting it binocular vision (and depth perception) which would be beneficial for hunting. It also had an acute sense of smell, which would have been useful for locating prey or carcasses.

Tiny arms mystery

One of the ongoing mysteries surrounding T. rex is the function of its relatively tiny arms. While they were small, they were extremely muscular. 

Some theories suggest they were used for grasping during mating, or to help push the dinosaur up from a resting position.


T. rex existed until the end of the Cretaceous period, approximately 66 million years ago, when a mass extinction event (often associated with an asteroid impact) led to the demise of all non-avian dinosaurs.

Cultural impact

The T. rex has left a significant mark on popular culture, featuring prominently in books, movies, and television shows. Its most notable appearance is probably in the “Jurassic Park” franchise.

The study is published in the journal Cretaceous Research.

Image Credit: Andrey Atuchin


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