Plesiosaur fossils found in the Sahara suggest they weren't just marine animals

Small plesiosaur fossils, long-necked marine reptiles from the dinosaur era, were discovered in the Sahara Desert of Morocco, a 100 million year old river system. This finding shows that some plesiosaur species, which were previously believed to be marine creatures, may have really resided in freshwater.

Plesiosaurs were ancient reptiles with small heads, long necks, and four long flippers. Mary Anning, a fossil researcher, discovered them for the first time in 1823. Plesiosaurs were sea animals, or were popularly believed to be, unlike the Loch Ness Monster, which is what inspired reconstructions of it.

Now, researchers from Université Hassan II in Morocco, University of Bath, and University of Portsmouth in the UK have reported finding tiny plesiosaurs in an African river that dates back to the Cretaceous.

The fossils include teeth and bones from three-meter-long adults as well as an arm bone from a newborn that was just 1.5 meters long. They imply that these animals regularly inhabited freshwater habitats and subsisted there, sharing it with frogs, crocodiles, turtles, fish, and the enormous aquatic dinosaur Spinosaurus.

The plesiosaurs may have even spent their whole lives in freshwater, like modern river dolphins, according to these fossils, which indicate they were designed to dwell there.

Georgina Bunker, a student at the University of Bath, Nick Longrich from the Milner Centre for Evolution at the University of Bath, David Martill, Roy Smith, and Samir Zouhri from the University of Hassan II served as the paper's lead authors.

The fossils include arm bones from immature juveniles, shed teeth, and vertebrae from the neck, back, and tail.

Although it may seem flimsy, isolated bones really reveal a lot about the ancient ecosystems and the creatures that lived there. They provide you more information to work with because they are so much more prevalent than skeletons, according to Dr. Nick Longrich, the paper's corresponding author.

"The bones and teeth were not found together as a skeleton, but rather dispersed and in several locations. Therefore, every tooth and bone represents a distinct species. The number of creatures in this collection is over a dozen.

The location of an animal's death may be determined by its bones, but its living environment can be determined by its teeth, which were lost while the animal was still alive.

Additionally, the teeth exhibit severe wear, similar to that of the fish-eating dinosaur Spinosaurus discovered in the same beds.

By chipping their teeth on the armored fish that dwelt in the river, the plesiosaurs were likely consuming the same diet, according to the experts. This suggests they were frequent users of the river rather than just passing through.

The abundance of plesiosaur fossils in the river suggests that's improbable, despite the fact that aquatic creatures like whales and dolphins often go up rivers, either for food or because they're lost.

The ability of the plesiosaurs to endure both fresh and salt water, like some whales, such the beluga whale, is a more feasible hypothesis.

It's also conceivable that, like contemporary river dolphins, the plesiosaurs lived in the river permanently. Due to their little size, plesiosaurs could have hunted in shallow rivers, and the fossils reveal an extraordinary diversity of fish species.

We don't fully understand why the plesiosaurs exist in freshwater, according to Dr. Longrich.

It's a little debatable, but who's to say that just because we paleontologists have referred to them as "marine reptiles" all along, that means they had to dwell in the sea? Many marine lineages migrated into freshwater.

In the Ganges River, the Yangtze River, and again in the Amazon River, freshwater dolphins underwent at least four evolutionary cycles. Lake Baikal in Siberia is home to a type of freshwater seal, suggesting that plesiosaurs may have also evolved to live in freshwater.

The plesiosaurs are little plesiosaurs that are frequently discovered in brackish or freshwater in other parts of England, Africa, and Australia. They are members of the family Leptocleididae. Additionally, additional plesiosaurs, such as the long-necked elasmosaurs, have been discovered in fresh or brackish seas in China and North America.

There were plesiosaurs for more than 100 million years, and they were a diversified and versatile group. The authors speculate that they may have frequently infiltrated freshwater to varying degrees based on what they have discovered in Africa and what other scientists have discovered elsewhere.

"Honestly, we don't really know. Paleontology operates in this manner. How can paleontologists be confident about the life of extinct creatures, a question that is frequently raised by the public? We can't always, it's a fact. We are only able to make informed assumptions based on the data we currently have. More fossils will be discovered. They might confirm those conjectures. Possibly not.

Lead author Georgina Bunker stated, "It's been incredibly intriguing to watch the path this project has gone in. A single bone served as the study's starting point as an undergraduate project, but when more plesiosaur fossils were discovered throughout time, a clearer image of the animal steadily emerged.

The latest finding increases the Cretaceous' variety in Morocco. The finding, according to Dr. Samir Zouhri, "adds to the countless discoveries we have made in the Kem Kem during the previous fifteen years of study in this part of Morocco and is yet another remarkable discovery." The Cretaceous biodiversity hotspot Kem Kem was simply amazing.

What astounds me, according to co-author Dave Martill, is how many carnivores coexisted in the old Moroccan river. This was not the spot to go swimming.

What does this suggest, though, in terms of the likelihood of anything like a Loch Ness Monster? It makes sense on a certain level. Plesiosaurs lived in freshwater habitats as well as the sea. However, the fossil record also implies that the final plesiosaurs perished 66 million years ago, around the same time as the dinosaurs, after about 150 million years.

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