A giant mosasaur from Morocco’s Late Cretaceous period that could have grown up to eight meters in length is the third new species to be described in the region in less than a year, bringing the total number of species to at least 13 .
The great diversity of fauna shows how mosasaurs, the giant marine lizards related to snakes and Komodo dragons, flourished in the last million years of the Cretaceous period before they, and especially species on Earth, were devastated by the impact of a giant. asteroid 66 million years ago.
The new species, named Pluridens serpentis, had long, slender jaws with over a hundred sharp, fangliform teeth for catching small prey like fish and squid. Compared to related species, it had small eyes, which suggests poor vision. But the muzzle had dozens of openings for nerves, hinting at the ability to hunt by sensing water movement and pressure changes. These nerves may have been sensitive to tiny changes in water pressure, an adaptation seen in sea snakes.
“Typically when animals develop small eyes it is because they are more dependent on other senses,” said Dr Nick Longrich, senior lecturer at the Milner Center for Evolution at the University of Bath, who led the study.
The fact that Pluridens has so many nerves in his face may mean he used changes in water pressure to detect animals in low light conditions, either at night or in deep, dark water. Mosasaurs may also have had other senses available to them.
“If he didn’t use the eyes, then it was very likely that he was using the tongue to hunt, like a snake,” he said. “Many snakes and aquatic lizards – sea snakes, lime snakes, water monitors – wave their forked tongues underwater, using chemical signals to track their prey. Mosasaurs are said to have resembled whales and dolphins, so it’s tempting to assume that they lived like them.
“But they’re very different beasts – they’re huge lizards – so they probably acted like them.”
While most of his parents were small, barely a few meters long, Pluridens grew to be tall, perhaps eight meters long. The larger individuals had thick, heavily built jaws.
“It’s possible that big males will fight with these jaws,” Dr Longrich said. “In some beaked whales, the males have massive jaws that they fight with, and the male sperm whales can be very aggressive. Some Pluridens jaws show healing wounds, suggesting heavy fighting.”
Moroccan mosasaurs were extremely diverse. Some had small teeth for gripping fish and squid, others had blunt teeth for crushing crustaceans, clams and ammonites, while others had teeth designed to cut or tear other marine animals – including other mosasaurs.
Pluridens brings the number of mosasaurs known from Morocco’s Late Cretaceous to 13, but researchers suggest it is unlikely to be the last new species.
Dr Longrich said: “The diversity of these fossils is simply astonishing. Far from declining in diversity, mosasaurs seem to reach their peak just before they became extinct.
“We see no evidence that this group struggled before they died out – Evolutionarily they were successful, they did everything right – but nothing can prepare you for an asteroid.”
Co-author of the study, Dr Nour-Eddine Jalil from the Museum of Natural History of the University of Sorbonne (France) declared: “It is a new species of large predator which, with its eight meters of length, confirms the diversity of sea fauna just before the Cretaceous crisis.
“Pluridens serpentis emphasizes the importance of Morocco’s paleontological heritage in helping to illustrate the history of life.”
Dr Nathalie Bardet, specialist in mosasaurs, in particular those of the Phosphates of Morocco, at the National Museum of Natural History in Paris, was also co-author of the article.
She said: “Working on this group of marine reptiles for over 20 years, I never cease to be surprised by the incredible diversity of these predators, who all lived there and shared available space and food resources.
“These latest discoveries perfectly show that the list of species present here is far from closed and that the future still holds great surprises and discoveries!”
The study, carried out in collaboration with researchers from the Museum of Natural History of the Sorbonne University (France), the Office Chérifien des Phosphates (OCP) and the Cadi Ayyad University (Morocco), is published in Cretaceous research.