Plesiosaur fossils present in strata related to a 100-million-year-old river system show that some plesiosaurs, historically regarded as marine animals, could have lived in freshwater. These long-necked, piscivores co-existed with the enormous dinosaur Spinosaurus (S. aegyptiacus).
Scientists from the College of Tub and College of Portsmouth within the UK, and Université Hassan II (Morocco), have reported proof small plesiosaurs from Kem Kem Group deposits in Morocco.
The fossils embody bones and tooth from three-metre-long adults and an arm bone (humerus) from a 1.5- metre-long juvenile. They trace that these creatures routinely lived and fed in freshwater, alongside frogs, crocodiles, turtles, fish, and the large aquatic dinosaur Spinosaurus.
When is a “Marine Reptile” a Marine Reptile?
The Plesiosauria clade was a long-lived and extensively distributed group of marine reptiles. Most fossils, which date from the Higher Triassic to the tip of the Cretaceous (Maastrichtian faunal stage), are related to marine deposits, however a couple of specimens have been present in strata related to brackish and freshwater environments. The researchers report plesiosaurs from river deposits of the Kem Kem Group. The quite a few shed tooth present heavy put on just like that noticed in within the tooth of coeval spinosaurids. Up to date plesiosaur fossils from the Bahariya Formation of Egypt have been recognized as examples of the Polycotylidae plesiosaur household. The Kem Kem fossils in all probability symbolize leptocleidid plesiosaurs. Most Leptocleididae fossils come from shallow nearshore, brackish or freshwater palaeoenvironments suggesting that these small-bodied plesiosaurs had been tailored to shallow, low-salinity environments.
Because the fossil plesiosaur tooth present the identical indicators of wear and tear because the tooth of Spinosaurus, the researchers indicate that the plesiosaurs had been consuming the identical meals – chipping their tooth on the armoured fish that lived within the river. This means that they spent loads of time within the river, quite than being occasional guests.
As different kinds of Mesozoic marine reptile (mosasaurids and the crocodile-like teleosaurids), are thought to have inhabited (at the least a few of the time), freshwater environments, this implies that so-called “marine reptiles” could have thrived in non-marine habitats.
Co-author of the scientific paper, Dr Nick Longrich (College of Tub Milner Centre for Evolution), commented:
“It’s scrappy stuff, however remoted bones really inform us so much about historical ecosystems and animals in them. They’re a lot extra frequent than skeletons, they provide you extra info to work with. The bones and tooth had been discovered scattered and in several localities, not as a skeleton. So, every bone and every tooth is a distinct animal. We have now over a dozen animals on this assortment.”
Numerous and Assorted Kem Kem Group Freshwater Fauna
Whereas extant marine mammals like whales and dolphins wander up rivers, both to feed or as a result of they’re misplaced, the variety of plesiosaur fossils within the river deposits recommend that’s unlikely. The group recognized cervical, dorsal and caudal vertebrae, numerous tooth and the humerus from a juvenile. The researchers postulate that the plesiosaurs had been capable of tolerate contemporary and salt water, like some whales, such because the beluga whale (Delphinapterus leucas).
Co-author Dr Samir Zouhri stated:
“That is one other sensational discovery that provides to the numerous discoveries we have now made within the Kem Kem over the previous fifteen years of labor on this area of Morocco. Kem Kem was actually an unimaginable biodiversity hotspot within the Cretaceous.”
Plesiosaurs – Freshwater Incursions
The researchers compiled a listing of all of the geological formations which have proven proof for the presence of members of the Plesiosauria clade in brackish or freshwater. Having collated this info, they re-examined the information figuring out the various kinds of plesiosaur related to the deposit.
Consequently, a map documenting the incidences of freshwater incursions by totally different plesiosaur sorts was produced.
For the important thing to the geological formations see the tip of this text.
Co-author David Martill (College of Portsmouth) exclaimed:
“What amazes me is that the traditional Moroccan river contained so many carnivores all residing alongside one another. This was no place to go for a swim.”
Key to the Geological Formations Featured within the Plesiosaur Map
Geographic distribution of non-marine Plesiosauria Formations: 1, Dinosaur Park Formation (Campanian); (2), Horseshoe Canyon Formation (Campanian – Maastrichtian); 3, Isachsen Fm. (Late Aptian); 4, Strand Fiord Formation (Turonian – Coniacian); 5, Nice Estuarine Group (Bathonian); 6, La Colonia Formation (Higher Campanian – Decrease Maastrichtian); 7, Wadhurst Clay Formation (Valanginian); 8, Tunbridge Wells Sands Formation (Higher Valanginian); 9, Wessex Formation (Barremian); 10, Higher Weald Clay Formation (Barremian); 11, Vectis Formation (Barremian – Aptian); 12, Obernkirchen Sandstone (Late Berriasian);
13, Bükerberg Formation (Berriasian); 14, Kem Kem beds (Cenomanian – Albian?); 15, Chenini Formation (Albian); 16, Bahariya Formation (Cenomanian), 17, Sunday River Formation (Valanginian); 18, Lianmugin Formation (Higher Aptian); 19, Xinhe Formation (Center Jurassic); 20, Ziliujing Formation (Toarcian); 21, Xintiangou Formation (Center Jurassic), 22, Xiashaximiao Formation (Center Jurassic); 23, Shezi Formation (Higher Triassic); 24, Razorback Beds (Sinemurian); 25, Evergreen Formation (Pliensbachian – Toarcian); 26, Griman Creek Formation (Albian); 27, Eumeralla Formation (Aptian) 28; Wonthaggi Formation (Valanginian – Aptian), 29 Eumeralla Formation (Higher Aptian – Decrease Albian). Word that some formations comprise a couple of prevalence.
Every little thing Dinosaur acknowledges the help of a media launch from the College of Tub within the compilation of this text.
The scientific paper: “Plesiosaurs from the fluvial Kem Kem Group (mid-Cretaceous) of jap Morocco and a assessment of non-marine plesiosaurs” by Georgina Bunker, David M. Martill, Roy Smith, Samir Zouhri and Nick Longrich.