Plesiosaur fossil found in Morocco shows the marine animals also lived in freshwater

Even better is when the two worlds of science fact and mythology cross over. A new fossil discovery in Morocco has sent imaginations racing once again.

One of the most famous cryptids (animals unknown to science but said to exist by those who claim to have seen them, or signs of them) is the fabled Loch Ness monster, or "Nessie", believed by some to live in the Scottish Highlands lake called Loch Ness.

We could throw into the mix the animal known as "Champ" which is said to live in Lake Champlain which crosses the border between Canada and the north-eastern United States.

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While proof of Nessie and Champ's existence remains elusive, for hundreds of years, visitors to the lakes have insisted they have seen the animals.

Attempts to give scientific credence to the myths have included suggestions that Nessie and Champ may be the last vestiges of a by-gone age.

First found and described in 1823 by palaeontologist Mary Anning, plesiosaurs are long-necked, small-headed, flippered marine reptiles which lived during the time of the dinosaurs.

Their body shape matches the long neck, smooth, scaly skin, and undulating serpentine body ascribed to Nessie and Champ by alleged witnesses.

It is extremely unlikely that a population of animals would have gone unnoticed and left no trace for 66 million years to the point of making this theory simply untenable.

But, putting that to one side, there is another major problem: Both Lake Champlain and Loch Ness are freshwater lakes.

See, plesiosaurs were marine reptiles, meaning that they lived exclusively in saltwater.

That is, we thought they did. Until now.

Scientists from the University of Bath and University of Portsmouth in the UK have published their findings of a new extinct plesiosaur in the journal Cretaceous Research.

The plesiosaur fossils were discovered in the Kem Kem Geological Group in eastern Morocco near the border with Algeria.

The Kem Kem is home to many famous discoveries including the massive carnivorous dinosaurs Carcharodontosaurus and Spinosaurus.

One specimen is that of a 1.5-metre-long baby which lived 100 million years ago. The animal was found in what is now dry Morocco but would have been a river during the Cretaceous period.

The fossils hint that the creatures lived and fed in freshwater alongside giant crocodiles and Spinosaurus which is thought to be aquatic.

Not only does the find suggest that the plesiosaurs could tolerate freshwater, but that they may even have spent their lives there, the researchers say.

Included among the fossils are neck, back and tail vertebrae, teeth, and a piece of the juvenile's forelimb.

"It's scrappy stuff, but isolated bones actually tell us a lot about ancient ecosystems and animals in them. They're so much more common than skeletons, they give you more information to work with" says corresponding author Dr Nick Longrich, a University of Bath palaeontologist.

"The bones and teeth were found scattered and in different localities, not as a skeleton. So each bone and each tooth is a different animal. We have over a dozen animals in this collection."

Bones tell us where the animals died. But the heavily worn teeth were shed while the animals were still alive, hinting at the fact that the site is not just where they died, but where they lived as well.

Modern marine animals like whales and dolphins sometimes wander into rivers to feed or because they are lost. But the number of plesiosaur fossils makes this an unlikely scenario for the Cretaceous animals.

It is more likely that the plesiosaurs, more like beluga whales, are able to tolerate both fresh and salt water.

The animals could even have been permanent freshwater inhabitants like some modern dolphins which have evolved to be freshwater specialists four times - in the Ganges River, the Yangtze River and twice in the Amazon.

"We don't really know why the plesiosaurs are in freshwater," adds Longrich.

"It's a bit controversial, but who's to say that because we palaeontologists have always called them 'marine reptiles', they had to live in the sea? Lots of marine lineages invaded freshwater."

The Moroccan plesiosaurs belong to the family Leptocleididae.

These smaller plesiosaurs have been found around the world including in England, Africa and Australia.

A diverse and adaptable group of animals, plesiosaurs swam Earth's ancient oceans for over 100 million years. The scientists believe they may even have invaded freshwater to different degrees multiple times.

"We don't really know, honestly. That's how paleontology works.

"People ask, how can paleontologists know anything for certain about the lives of animals that went extinct millions of years ago? The reality is, we can't always.

"All we can do is make educated guesses based on the information we have. We'll find more fossils. Maybe they'll confirm those guesses. Maybe not," says Longrich.

The researchers say that the new discovery increases the diversity of Cretaceous Morroco.

"This is another sensational discovery that adds to the many discoveries we have made in the Kem Kem over the past fifteen years of work in this region of Morocco," explains team member and co-author Samir Zouhri of the Moroccan Hassan II University of Casablanca.

"Kem Kem was truly an incredible biodiversity hotspot in the Cretaceous."

"What amazes me" says co-author Dave Martill, "is that the ancient Moroccan river contained so many carnivores all living alongside each other. This was no place to go for a swim."

So, it is plausible that Nessie and Champ are real and that they are freshwater plesiosaurs. But don't hold your breath.

As much as we want to believe, this fact-hardened author agrees with scientific consensus that plesiosaurs died out with large dinosaurs 66 million years ago.