South American Elasmosaur

South American ElasmosaurIndeterminate Species
Classification
Domain	Eukaryota
Kingdom	Animalia
Phylum	Chordata
Subphylum	Vertebrata
Superclass	Tetrapoda
Clade	Sauropsida
Class	Reptilia
Superorder	Sauropterygia
Order	Plesiosauria
Superfamily	Plesiosauroidea
Clade	Cryptoclidia Xenopsaria
Family	Elasmosauridae
Presence
Location	Kawas Sea, South America
Temporal Range	72 million years ago, Maastrichtian Stage, Late Cretaceous Period
Episodes	Freshwater (Segment 6)
Characteristics
Diet	Piscivorous

“ The river water is now approaching the sea. A taste of salt in its waters is already detectable. At high tide, visitors come in from the open sea to explore these channels. Elasmosaurs. These are true ocean-going reptiles. But some come to estuaries to explore the brackish waters. ”

― David Attenborough, Freshwater

Present on Prehistoric Planet is an unnamed elasmosaurid plesiosaur that lived in South America during the Maastrichtian stage of the Late Cretaceous Period. It is possible that this species is Kawanectes (Kawas Swimmer), a small elasmosaur that lived in the Allen and La Colonia Formations of Argentina, 72 million years ago, during the Maastrichtian stage of the Late Cretaceous Period.

Paleobiology

Not much can be assumed regarding this elasmosaur, given how its identity remains unconfirmed. Assuming it is intended to be Kawanectes, this animal would have measured merely 3.8 meters (12 feet, 6 inches) long and weighed around 140 kilograms (310 pounds).

Prehistoric Planet depicts this animal with an almost-bleached skin color and dark Turkish stripes. It is otherwise very similar to Tuarangisaurus in appearance except for its stripes, which are slightly more prominent.

Paleoecology

Paleoenvironment

A river in South America leading to the open sea

“ Now, the millions of tons of sediment carried here by rivers is finally delivered into the sea. The river water takes time to mix with the ocean, and, for a while, the two waters flow side by side. Nonetheless, great shoals of fish find plenty on which to feed in these waters. ”

― David Attenborough, Freshwater

The unnamed South American elasmosaur is depicted living in the rivers and estuaries leading into the Kawas Sea, an ancient extension of the Atlantic Ocean that covered most of Patagonia during the Late Cretaceous Period. If the animal is indeed Kawanectes lafquenianum, it would have lived in the Allen and La Colonia Formations of Argentina. Both areas are known to contain lakes, rivers, estuaries, and coastal environments.

Hunting Tactics and Feeding Preferences

Like most of their relatives, these plesiosaurs are depicted as being primarily piscivorous, using their needle-like teeth to grip fish as well as other types of suitable prey like cephalopods. Though plesiosaur necks are rigid and thus incapable of flexibly whipping around to snap up prey from any direction, it is believed that plesiosaurs evolved their long necks so that their heads could ambush and grab fish right before their prey can be alerted by the sight and pressure exerted by their massive bodies. With large eyes directed relatively upward and a strong sense of smell, the elasmosaurs are able to close in on their prey even in murky waters.

Appearance

In the sixth and final segment of Freshwater, in the forests of South America, elasmosaurs journey down a river flowing through a mangrove, with a Quetzalcoatlus watching them curiously. The elasmosaurs continue on to where the river widens, where more inhabitants of the forest (namely, what appears to be a juvenile Quetzalcoatlus and an Austroposeidon) take an interest in the peculiar presence of the normally ocean-dwelling creatures. The elasmosaurs eventually end up where the murky waters of the river meet and mingle with the sea. They pursue great schools of fish through the brackish waters, circling around them to agitate and pin them right where they want them to, leaping out of the water to catch mouthfuls of fish as they try to jump and escape.

“ The clouds of sediment conceal the fish if they're any distance away. But the elasmosaurs don't hesitate to swim into the murkiest of water to pursue their prey. There is no escape for the fish, even above the water. These elasmosaurs collect the last of the river's gifts before its traces are finally lost in the oceans of the Prehistoric Planet. ”

― David Attenborough, Freshwater

The elasmosaurs are seen diving in and out of the clouded boundary between river and ocean, catching as many fish as they can, and the segment ends with one last view of Patagonia from space.