Aug 26, 2022 I Paul Seaburn

Newly Discovered Prehistoric Giant Marine Reptile of Morocco Ate Sea Monsters

Loch Ness monster fans got a boost of hope recently when paleontologists studying fossils from Morocco found bones that seemed to indicate the freshwater rivers that once flowed in the area hundreds of millions of years ago were home to a small (relative to its giant brothers) species of plesiosaur – the long-necked marine dinosaur that many believe is what is living deep in Loch Ness – and that may prove plesiosaurs could survive in freshwater lakes like Loch Ness. Of course, this assumes that a group of these freshwater plesiosaurs survived the mass extinction event 66 million years ago and swam or walk-waded from balmy Morocco to the frigid waters of northern Scotland. However, before they even left, they may have had to face an even bigger challenge to their survival – a huge marine reptile larger than the biggest plesiosaurs that ate them and pretty much anything else in the prehistoric ocean for lunch. A new study reveals that researchers in Morocco have discovered the largest known species of Mosasaur – a monster big enough to make it the ultimate apex predator … threatening even to other mosasaurs. Are any of these creatures hiding somewhere?

Drawing of a momasaur

“Thalassotitan was an amazing, terrifying animal. Imagine a Komodo Dragon crossed with a great white shark crossed with a T. rex crossed with a killer whale.”

Dr. Nick Longrich, a paleontologist and evolutionary biologist at the University of Bath, led the research that found the fossils of a Thalassotitan atrox – the largest mosasaur to ever roam the high seas. As he explains in the University of Bath press release announcing the publication of his study published in the journal Cretaceous Research, Morocco was a hotbed of marine monsters during the last 25 million years of the Cretaceous Era before the Cretaceous–Paleogene extinction event, making the area a prime feeding ground for the many types mosasaurs of the period. While they are classified as marine lizards, there are no creatures today that resemble them – as we can see from Longrich’s scary description. Surprisingly, their closest modern relatives are not the surviving dinosaurs like alligators and crocodiles, but snakes and iguanas. Think about that on your next trip to Florida.

The phosphate fossil beds of Morocco have yielded fossils of many different mosasaur species with jaws filled with sharp teeth designed for the foods they liked best -- small and spiky for fish and squid; blunt teeth and crushing jaws for shelled creatures. However, it appears these apex predators ate everything -- fish, cephalopods, turtles, molluscs, birds and other mosasaurs. And the Thalassotitan seems to have been at the apex of the apex.

“Thalassotitan, had an enormous skull measuring 1.4 metres (5 feet long), and grew to nearly 30 feet (9 metres) long, the size of a killer whale. While most mosasaurs had long jaws and slender teeth for catching fish, Thalassotitan had a short, wide muzzle and massive, conical teeth like those of an orca. These let it seize and rip apart huge prey.”

While the jaws were impressive, the teeth of the Thalassotitan were not – the fossil remains were broken and worn. However, opinions changed when further study determined the cause – the teeth were broken and ground down to nubs and roots from attacking other giant marine reptiles and mosasaurs, biting through their bones, crunching them and gulping them down – the fragments were later heaved back up after the meat had been digested. Fossils found in the same area as the Thalassotitan included large predatory fish, a sea turtle, and a half-meter long plesiosaur head – that head had been completely bitten off before being digested and spat out. The fossils of prey also included the jaws and skulls of at least three different mosasaur species. It is that last menu item that intrigued Dr. Longrich. He found marks on the bones indicating violent fights that could only have been with other Thalassotitans – wounds in the face and jaw areas are clear indications of battles over food and sexual partners. (Many photos of the fossils can be seen here.)

“In the 25 million years before the asteroid struck, they just kept getting more diverse. More specialized. Bigger.”

While the discovery of this massive apex predator of the Cretaceous period is impressive, the real revelation from this Moroccan treasure trove of marine fossils is that the animals were not in decline – some paleontologists suggest dinosaurs and huge marine animals were already dying out when the Cretaceous–Paleogene extinction asteroid hit and this made them more vulnerable to the climate change that followed. Longrich disagrees … especially when it comes to the mosasaurs. He explains on his blog:

“Mosasaurs suggest the environment wasn’t deteriorating- they were thriving up until the point the asteroid hit. This is a group going out in a blaze of glory, not fading away. And I think mosasaurs- being predators- can serve as a proxy for the overall diversity of the marine ecosystem. They’re able to get more diverse because the marine fauna as a whole is getting more diverse. This has implications for understanding mass extinctions.”

In what is now Morocco 66 million years ago, the waters were so full of healthy marine life that giant mosasaurs like the Thalassotitan were able to gorge, grow, gorge and grow some more without harming the ecosystem. And the animals they consumed show no signs of dying out. And the plants THEY ate showed no signs of dying out. This was a prehistoric wonderland that was thriving … with no signs of slowing down. Nothing should have been able to stop it.

A recreation of a momasaur buffet?

“In this scenario, we have a highly diverse, functional ecosystem that was literally in a matter of weeks and months destroyed by a single, catastrophic, completely unpredictable event. This perspective on evolution is terrifying.”

Longrich calls this the “Sh*t Happens” evolution scenario – everything was going along great, creatures were making good choices and none were doing anything bad that would cause a catastrophe. The Cretaceous–Paleogene extinction event just happened – it was the fault of no creature on Earth. It was an example of bad things happening to good dinosaurs. Longrish says the idea that things happen randomly is terrifying, and he believes it is why the idea of a mass extinction caused by a massive asteroid impact was resisted by scientists for so long.

In case you‘re wondering how the Thalassotitan got so big and mean, Longrich has a theory on that too, and it is connected to another extinction event. – this one in the middle of the Cretaceous era. Somewhere around 95 million years ago, large numbers of volcanic eruptions filled the atmosphere with dust, resulting in climate change and global warming that caused the extinction of the apex predators of the time, but not the smaller ones. The survivors – smaller momasaurs, tyrannosaurs and other dinosaurs quickly took over and grew to massive sizes. They would have kept growing if it were not for the killer asteroid.

Sh*t happens.

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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