Discovery of dinosaurs in Morocco provides clues to why they disappeared

According to Nicholas R. Longrich, senior lecturer in paleontology, evolutionary biology, and life sciences at the University of Bath, says Africa's last dinosaurs, especially the diverse predatory dinosaurs, were thriving before their sudden extinction. From the depths of Moroccan phosphate, his theory will be confirmed

66 million years ago, the last dinosaurs disappeared from Earth. Scientists are still trying to understand why. New fossils of abelisaurs – distant relatives of the tyrannosaurid dinosaurs – from Morocco suggest that African dinosaurs remained diverse until their extinction. This supports the theory that their disappearance occurred suddenly, by the impact of a giant asteroid, as Nicholas R. Longrich, Lecturer in Paleontology, Evolutionary Biology and Life Sciences at the University of Bath.

In a contribution published in ConversationThe causes of this mass extinction have been debated for two centuries, the paleontologist recalls. Georges Cuvier, the father of paleontology, believed this was caused by disasters. On the other hand, Charles Darwin believed that progressive environmental changes and competition between species slowly led to the extinction of species lineages.

However, it has become clear, after research, that the Cretaceous Period (145 million years ago to 66 million years ago) ended with an extraordinary wave of extinction. A large number of species around the world have become extinct in a short period of time. The discovery of the 180-kilometre-wide crater of the asteroid Chicxulub in Mexico's Yucatan Peninsula points to the sudden extinction of dinosaurs and other species caused by the impact. But other studies have argued that a long, slow decline in dinosaur diversity contributed to their loss.

“Putting together history is difficult. Not only are dinosaur fossils extremely rare, the fossil record is also incomplete. Nicholas R. was angry. Longrich. And for good reason: most studies to date have been conducted in the Northern Hemisphere (the United States, Canada, or Mongolia), while research on dinosaurs from the southern continents has been rare, especially due to the inaccessible terrain of the tropics.

The table can also be biased, knowing that Africa, a massive continent, probably contains many more species of dinosaurs than North America, especially Morocco which is home to dinosaurs. “The most dangerous region in the history of Earth “.

However, the vast continent has few terrestrial rocks from the end of the Cretaceous period. “This is because levels of volcanic activity caused sea levels to rise, submerging much of Africa under shallow seas. Dinosaurs, being terrestrial, are rarely found in marine rocks. But rarely means never. Study enough fossils.” Marine and you will eventually find a dinosaur. Nicholas R. warns: Longrich.

And from Morocco, which has the largest phosphate deposits (in other words, ancient seabeds) dating back to the last million years of the age of the dinosaurs, crucial evidence emerges: they are full of ledges, fish scales and shark teeth, and are very large in size. Number of marine reptiles – mosasaurs, plesiosaurs, and sea turtles. But also dinosaur bones.

I read about it : In the footsteps of Spinosaurus in the Moroccan desert

Nicola R. wonders: Longrich on the reasons for the presence of these dinosaur bones in marine sediments in Morocco: Dinosaurs may have swum to the islands in search of food, as deer and elephants do today, and some may have drowned. Other dinosaurs may have been swept out to sea by floods or storms, or drowned in rivers that carried them to the ocean. Others may have died on the beach before being evacuated at high tide. However, a series of unlikely events transported the dinosaurs into the ocean.

“So, by studying the seafloor and working for many years, we have slowly built up a picture of the last dinosaurs in Africa, bone by bone.” Related paleontologist.

The last dinosaurs in Africa included titanosaur sauropods, long-necked herbivores the size of elephants. The niche of herbivores was occupied by horse-sized duck-billed dinosaurs.

I read about it : For the first time in Africa, the remains of duck-billed dinosaurs were discovered in Khouribga

“But carnivores are particularly interesting. They are at the top of the food chain, and they tell us a lot about the ecosystem. African predatory dinosaurs were diverse, with different herbivores, and large numbers of them. adds the specialist.

According to him, the main predator was a ten-meter-long animal called Chinanansaurus barbaricus. “So far, the Abelisauridae are known only from their jaws, but this tells us that they were part of the Abelisauridae, a strange family of carnivores found in South America, India, Madagascar, and Europe, while those dinosaurs dominated to the north. Abelisaurids had a short, sometimes bulldog snout. horns, and they had strange little short arms that made T. rex's arms look huge by comparison. Nicholas R. explains: Longreach.

What is new is the appearance of fossils of two new abelisaurs in Morocco.

I read about it : Discovery of fossils of “primitive T. rex cousins” in Morocco

One of them was identified by the leg. “It was smaller than a chinanosaurus, at about five meters long – small by dinosaur standards, but large for modern predators. Curiously, it resembled abelisaurus found in South America. It is possible that this was an ancient land connection that existed between continents since 100 million years ago. Or perhaps the abelisaurus swam the narrow sea route that separated the continents.

“Another bone comes from the foot of a smaller abelisaurid, only three meters long. Similar small abelisaurids existed in Europe, and this may be related to them.” The paleontologist advances.

Dinosaurs from the Upper Maastricht region of Morocco. Source: Nick Longrich.

In recent months, more dinosaur fossils and more species have been discovered. “We are still analyzing these fossils, so we can't say much at the moment, but finding so many species in a handful of fossils tells us that we are sampling a very diverse fauna.” The researcher concludes.

And to add to that “Although fossils from the Great Plains of North America may record a decline in dinosaur diversity, this may be a local rather than a global phenomenon. It is possible that global cooling during the last Cretaceous period hit higher latitude environments more severely, leading to “Reduced diversity. But the African dinosaur fauna suggests that at lower latitudes, dinosaurs thrived and even diversified. If this is the case, it means that dinosaurs were slaughtered at their peak.”

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As Nicholas R. believes Longrich notes that the last dinosaurs in Africa, especially the various predatory dinosaurs, were thriving before their sudden extinction: “Over more than 100 million years, it evolved and diversified, producing a remarkable diversity of species: predators, herbivores, aquatic species, even flying forms, and birds. Then, in one catastrophic moment, everything was wiped out during the months of darkness caused by the dust.” And the effects resulting from the asteroid's collision with Mexico. Of all these species, only six bird species survived the disaster…

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