Detected more than 200 years ago, plasiosaurus are among the most significant marine creatures of the dinosaur era; the vast majority of these reptiles have evolved into the sea, but some species may have adapted to freshwater ecosystems, especially in the Sahara desert.
Plesiosaurus is a group of marine reptiles that have been widely distributed in almost all seas from late trias to late chalk. Most fossils are found in sea sediments, but some occur in salty, low-salin or freshwater environments. In Cretaceous Research, a group of paleontologists report on the discovery of fossil remains of three new individuals in freshwater river sediments of the Kem-Kem formation, an extensive upper rock plateau in Morocco.
The fossil remains include several teeth, vertebrates and humerus. The first bone, 1.5 m long, is owned by a young person, and the vertebrae are likely to belong to two young adults about three metres long.
While modern plyziosaurs from the nearby Baharia formation in Egypt belong to Polycotylidae, these plyosaurs demonstrate the characteristics of Leptocleidae. These small plysiosaurs were widespread in the coastal and non-marine environments in the early chalk period, but these are the first freshwater fossils of plasiosaurus from Morocco.
Have these animals ever lived in this environment like modern river dolphins, or have they been able to switch between fresh and salty water? Paleontologists prefer the first hypothesis. The abundance of the teeth found suggests that these reptiles carried some degree of freshwater, but they admit that the matter has not yet been resolved.
We know that a giant spinosaurus terode was also hunted in these waters, yet the freshwater environment in this region may have been less dangerous than the marine environment.
At the end of the chalk period, Morocco had an ecosystem equal to none, where in most modern and ancient environments there was one or two large predatory species in Kem-Kem at the same time, with at least a dozen species at the same time.