Shortly before an asteroid changed everything, the Atlantic Ocean off what is now Morocco seethed with large predators, the list of which has just grown further. Even before this discovery some paleontologists considered the eastern Atlantic in the late cretaceous the most large predator-abundant ecosystem of all time, so a mosasaur larger than any modern shark or crocodile fits right in.
Pluridens serpentis is the name given in Cretaceous Research to the newly discovered mosasaur that may have had a hunting strategy reminiscent of modern sea snakes, but on an altogether different scale.
No complete P. serpentis skeletons have been found, but the size of the skulls suggests they grew to 5-6 meters long (16-20 feet), similar to the biggest salt-water crocodiles today. However, the limited pieces we have from the rest of their bodies are what one would expect of something much bigger – probably more than 10 meters long (33 feet).
Compared to other mosasaurs Pluridens had small eyes that indicate it either hunted in shallow waters where seeing was easy, or preferred to use other senses. Its snout was covered in tiny openings for nerves. These resemble, and probably functioned similarly to, those of sea snakes, which use them to detect changes in water pressure, indicating the presence of prey (hence the name P. serpentis). Their tongues may have also had the capacity to detect chemical tracers in the water.
“If it wasn’t using the eyes, then it’s very likely that it was using the tongue to hunt, like a snake,” said Dr Nick Longrich of the University of Bath in a statement. “Many aquatic snakes and lizards – sea snakes, filesnakes, water monitors – flick their forked tongues underwater, using chemical cues to track their prey. Mosasaurs would have resembled whales and dolphins, so it’s tempting to assume they lived like them. But they’re very different beasts – they’re huge lizards – so they probably acted like them.”
P. serpentis also had many small teeth (relative to its size) that resembled those of snakes more than its closest relatives.
There is a reason some people like to have long speculative debates about who would win in a contest between the world's largest predators: such encounters almost never happen. Distant habitats prevent polar bears versus tiger battles, for example. Most of Earth's ecosystems only support one or two large carnivores today, and the paleontological evidence is similar. Jurassic Park only produced such an array of terrifying beasts by bringing together creatures separated by millions of years or thousands of kilometers.
All of which makes the oceans of the Maastichtian age, 72.1-66 million years ago, an anomaly. Particularly puzzling are the conditions in what is now Morocco, then a shallow sea occupied by an array of predator species, some of them terrifyingly large.
P. serpentis is the 13th mosasaur species from Maastrichtian Morocco, including two other Pluridens species. Not all of these would have existed simultaneously, but it is still a remarkable number, particularly considering the same seas also hosted plesiosaurs, large sharks, and the occasional crocodilian. Many pterosaurs prowled the skies above. The region indicates an astonishing diversity and abundance of mid-sized predators, as well as giants like Pluridens, that seems to have been growing right up to the Cretaceous' sudden end.
Moreover, it is unlikely we have exhausted the stock of the era's sea monsters. It's just three months since a previous mosasaur from the same era was announced – a smaller species with shark-like teeth also discovered by Longrich – and another discovery was three months earlier still.