Scientists have discovered a new giant species of mosasaur, Pluridens imelaki, that lived around 66 million years ago, based on fossils found in Morocco's phosphate deposits in Khouribga. Measuring an estimated 9 meters long, the rare marine predator reveals that mosasaurs were more diverse and still evolving shortly before the mass extinction that ended the age of dinosaurs. Reconstructed skeleton of a Mosasaurus at the Maastricht Natural History Museum. / Ph. DR ‹ › A new sea monster that lived around 66 million years ago has been discovered in Morocco. Scientists have identified a new giant species of mosasaur, a prehistoric marine reptile, based on fossils found in the country's phosphate deposits. Named Pluridens imelaki, meaning «giant» in Arabic, the species is described in a study published on March 4 in the journal Diversity. Conducted by Nicholas R. Longrich from the University of Bath (UK) and Nour-Eddine Jalil from the Muséum National d'Histoire Naturelle in Paris and Cadi Ayyad University in Marrakech, the research explains that the fossil was discovered in Sidi Chennane, in Khouribga Province, within the Oulad Abdoun Basin, an area renowned for its exceptionally rich marine fossil deposits. «The late Maastrichtian phosphatic beds of Morocco preserve the most diverse known mosasaurid assemblage, and possibly the most diverse marine reptile fauna in the world», the researchers write. The sediments date to the Late Maastrichtian stage of the Late Cretaceous, shortly before the mass extinction event that wiped out the dinosaurs. A giant predator of ancient seas The newly described specimen consists of a nearly complete skull with associated lower jaws and teeth, currently housed at the Museum of Natural History of Marrakech. The skull measures about 1.25 meters in length, allowing scientists to estimate the animal's total body length at around 9 meters or more, comparable to some of the largest marine predators of its time. This size makes Pluridens imelaki the largest known member of its group, the Halisaurinae, a subfamily of mosasaurs that dominated the seas during the final 25 million years of the Cretaceous. The new species displays several distinctive features that set it apart from other mosasaurs. Its skull was long and narrow, with very slender jaws and about 25 teeth in the lower jaw. Despite its massive size, the reptile likely fed on relatively small, soft-bodied prey, as its long jaws were not adapted for crushing large animals. The animal likely lived in shallow coastal waters, as the region that is now Morocco was covered by a shallow marine embayment along the Atlantic margin during the Late Cretaceous. A surprisingly rare species What makes the discovery particularly intriguing is its extreme rarity. Only one specimen of the species has been found despite decades of fossil collecting in the region. «Pluridens imelaki appears to have been exceptionally rare in the phosphates, being documented by only a single specimen among the many hundreds of mosasaur remains recovered». The discovery suggests that halisaurine mosasaurs were more diverse than previously thought. It also indicates that these marine reptiles were still evolving and diversifying shortly before the mass extinction that ended the age of dinosaurs.
