Scientists discover fossils of giant sea lizard that ruled the oceans 66 million years ago


Artist representation of Thalassotitan atrox. Credit: Andrey Atuchin

Researchers have discovered a huge new mosasaur from Morocco, called Thalassotitan atrox, that filled the apex predator’s niche. With huge jaws and teeth like those of killer whales, Thalassotitan hunted other marine reptiles – plesiosaurs, sea turtles and other mosasaurs.

At the end of the Cretaceous, 66 million years ago, sea monsters really existed. While dinosaurs thrived on land, the seas were ruled by the mosasaurs, giant marine reptiles.

Mosasaurs were not dinosaurs, but huge sea lizards that could grow up to 12 meters in length. They were distant relatives of modern iguanas and monitor lizards.

Mosasaurs looked like a Komodo dragon with fins instead of legs and a shark-like tail fin. Mosasaurs grew larger and more specialized in the last 25 million years of the Cretaceous Period, occupying niches once filled by marine reptiles such as plesiosaurs and ichthyosaurs. Some evolved to eat small prey such as fish and squid. Others crushed ammonites and mussels. The new mosasaur, called Thalassotitan atrox, evolved to prey on all other marine reptiles.

The remains of the new species were unearthed in Morocco, about an hour outside of Casablanca. Here, towards the end of the Cretaceous, the Atlantic Ocean flooded North Africa. Nutrient-rich waters welling up from the depths fueled plankton blooms. Those fed small fish, fed bigger fish, fed mosasaurs and plesiosaurs — and so on, these marine reptiles becoming food for the giant, carnivorous Thalassotitan.

Researchers discover fossils of giant sea lizard that ruled the oceans 66 million years ago

Nick Longrich with the mosasaur fossil. Credit: Nick Longrich

Thalassotitan had a huge skull measuring 1.4 meters (5 feet long) and grew almost 9 meters long, the size of a killer whale. While most mosasaurs had long jaws and slender teeth for catching fish, Thalassotitan had a short, broad snout and massive, conical teeth like those of a killer whale. These allow it to grab and shred huge prey. These adaptations suggest that Thalassotitan was an apex predator that was at the top of the food chain. The giant mosasaur occupied the same ecological niche as today’s killer whales and great white sharks.

Thalassotitan’s teeth are often broken and worn, but eating fish would not have caused this kind of tooth wear. Instead, this suggests that the giant mosasaur attacked other marine reptiles, chipping, breaking and grinding its teeth as it bit into their bones and tore them apart. Some teeth are so badly damaged that they have been ground down almost to the root.

Fossilized Prey Remains

Remarkably, possible remains of the victims of Thalassotitan have been discovered. Fossils from the same beds show acid damage, eating away teeth and bones. Fossils with this peculiar damage include large predatory fish, a sea turtle, a six-foot-long plesiosaur head, and jaws and skulls from at least three different mosasaur species. They would have been digested in Thalassotitan’s stomach before he spat out their bones.

Researchers discover fossils of giant sea lizard that ruled the oceans 66 million years ago

Size comparison of Thalassotitan atrox. Credit: Nick Longrich

“It’s circumstantial evidence,” says Dr. Nick Longrich, senior lecturer at the Milner Center for Evolution at the University of Bath and lead author of the study, published in Chalk research.

“We can’t say for sure what species of animal ate all these other mosasaurs. But we have bones from marine reptiles that were killed and eaten by a large predator.

“And in the same location we find Thalassotitan, a species that fits the profile of the killer – it’s a mosasaur that specializes in hunting other marine reptiles. That’s probably no coincidence.”

Thalassotitan was a threat to everything in the oceans, including other Thalassotitan. The huge mosasaurs bear injuries sustained in violent battles with other mosasaurs, with injuries to their faces and jaws sustained in combat. Other mosasaurs show similar injuries, but in Thalassotitan these wounds were exceptionally common, indicating frequent, intense battles over food grounds or mates.

“Thalassotitan was an amazing, terrifying animal,” said Dr. Nick Longrich, who led the study. “Imagine a Komodo dragon crossed with a great white shark crossed with a T. rex crossed with an orca.”

The new mosasaur lived in the last million years of the dinosaur age, a contemporary of animals like T. rex and Triceratops. Together with recent discoveries of mosasaurs from Morocco, it suggests that mosasaurs were not in decline before the asteroid impact that caused the Cretaceous mass extinction. Instead, they thrived.

Researchers discover fossils of giant sea lizard that ruled the oceans 66 million years ago

Map of distribution of Thalassotitan. Credit: Nick Longrich

Professor Nour-Eddine Jalil, a co-author of the paper from the Museum of Natural History in Paris, said: “Morocco’s phosphate fossils provide an unparalleled window into paleobiodiversity at the end of the Cretaceous.

“They tell us how life was rich and varied just before the end of the ‘dinosaur age’, where animals had to specialize to gain a place in their ecosystems. Thalassotitan completes the picture by playing the role of megapredator at the top. of the food chain.”

“There’s still so much to do,” Longrich said. “Morocco has one of the richest and most diverse marine faunas known from the Cretaceous Period. We are just beginning to understand the diversity and biology of the mosasaurs.”

Giant sea lizard fossil shows diversity of life before asteroid hit

More information:
Nicholas R. Longrich et al, Thalassotitan atrox, a giant predatory mosasaurid (Squamata) from the Upper Maastrichtian Phosphates of Morocco, Chalk research (2022). DOI: 10.116/j.cretres.2022.105315

dr. Longrich blogged about the research here:

Provided by the University of Bath

Quote: Scientists discover fossils of giant sea lizard that ruled the oceans 66 million years ago (2022, August 24), recovered on August 24, 2022 from

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The Valley Voice
The Valley Voice
Christopher Brito is a social media producer and trending writer for The Valley Voice, with a focus on sports and stories related to race and culture.


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