New fossils tell of their rise and fall

Sixty-six million years ago, sea monsters did exist. They were mosasaurs, huge marine lizards that lived at the same time as the last dinosaurs. Growing up to 12 meters in length, mosasaurs resembled a Komodo dragon with fins and a shark’s tail. They were also extremely diverse, with dozens of species evolving to occupy different niches. Some ate fish and squid, some – molluscs or ammonites.

now we found a new mosasaur hunt large marine animals, incl another mosasaurs.

new kind Thalassotitan atroxwas excavated in the Oulad Abdoun basin in the province of Khuribga, an hour’s drive from Casablanca in Morocco.

At the end of the Cretaceous period, sea ​​level was high, flooding most of Africa. Ocean currents driven by the trade winds pulled nutrient-rich bottom waters to the surface, creating a thriving marine ecosystem. The sea was full of fish, which attracted predators – mosasaurs. They brought their predators, the giant thalassotitan. At nine meters long and with a massive 1.3 meter long head, it was the deadliest animal in the sea.

Most mosasaurs had long jaws and small teeth to catch fish. But Thalassotitan was built quite differently. It had a short broad muzzle and strong jaws like those of a killer whale. The back of the skull was wide to attach the large jaw muscles, giving it a strong bite. Anatomy tells us that this mosasaur was adapted for attack and tearing large animals.

Massive, conical teeth resemble killer whale teeth. And the tips of these teeth are jagged, broken and turned. Such severe wear—not seen in fish-eating mosasaurs—suggests that Thalassotitan damaged its teeth by biting into the bones of marine reptiles such as plesiosaurs, sea turtles, and other mosasaurs.

In the same place we found what appeared to be the petrified remains of his victims. The rocks that make up the skulls and skeletons of Thalassotitan are full of partially digested bones of mosasaurs and plesiosaurs. The teeth of these animals, including a half-meter skull with a long neck plesiosaurus, were partially eaten away by the acid. This indicates that they were killed, eaten and digested by a large predator, which then spat out the bones. We can’t prove they were eaten by a Thalassotitan, but it fits the profile of the killer and nothing else fits, making him the prime suspect.

Thalassotitan, which is at the top of the food chain, also tells us a lot about ancient marine food chains and how they evolved during the Cretaceous period.

Evolution of the killer

The discovery of Thalassotitan tells us about marine ecosystems just before the asteroid hit 66 million years ago that ended the age of the dinosaurs.

Thalassotitan was just one of a dozen species of mosasaur living in Moroccan waters. The mosasaurs were part of the thousands of species that live in the oceans, but the fact that the predators were so diverse suggests that the lower levels of the food chain were also diverse enough for the oceans to feed them all. This means that the marine ecosystem was not in decline before the asteroid hit.

Instead of them, mosasaurs and other animals — plesiosaurs, giants sea ​​turtlesammonites, countless species of fish, molluscs, sea urchins, crustaceans – flourished and then suddenly died out when Asteroid Chicxulub with a width of 10 kilometers crashed into the earth, throwing dust and soot into the air and blocking out the sun. The extinction of the mosasaur was not a predictable result of gradual environmental change. It was an unpredictable result of a sudden disaster. How lightning strike from the clear blue sky, their end was swift, final, unpredictable.

But the evolution of the mosasaur could also have started with a catastrophe. It is interesting that the evolution of giant carnivorous mosasaurs resembles the evolution of another family of predators – Tyrannosauridae. The giant T. rex evolved on land around the same time that mosasaurs became top predators in the seas. Is this a coincidence? Maybe not.

And mosasaurs, and tyrannosaurs begin to diversify and became larger at the same time, about 90 million years ago, in Turonian stage of the Cretaceous. This happened after major extinctions on the ground and in the sea about 94 million years ago, at the Cenomanian-Turonian boundary.

These extinctions are linked to extreme global warming—a “supergreenhouse” climate caused by volcanoes that emit C02 into the atmosphere. In the future, giant predatory plesiosaurs disappeared from the seas and giant allosaurid predators were destroyed on earth. When the predator niches became vacant, mosasaurs and tyrannosaurs moved into the top predator niche. Although they were destroyed by mass extinctionThalassotitan and T. rex only evolved due to mass extinction.

The bigger they are, the harder they fall

Top predators are fascinating because they are large, dangerous animals. But their size and position at the top of the food chain also make them vulnerable. As you progress up the food chain, you have fewer animals. It takes a lot of small fish to feed a big fish, a lot of big fish to feed a small mosasaur, and a lot of small mosasaurs to feed one giant mosasaur. This means top predators are rare. And top predators require a lot of food, so they are in trouble when the food supply is disrupted.

As the environment deteriorates, dangerous predators can quickly become endangered species.

It is this sensitivity to environmental change that makes predators like Thalassotitan so interesting to study extinction. They suggest that being a top predator is a risky evolutionary strategy. Over a short period of time, evolution drives the evolution of larger and larger predators. Their size means they can fight for prey and knock it down. But for a long time, specialization for the top a predator niche increases vulnerability to disasters. Eventually, a mass extinction wipes out the top predators, and the cycle begins again.

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