Elasmosaurus Platyurus or Elasmosaurus was an extinct genus of Mesozoic marine reptiles. The precise definition of its name is “flat-tailed,” whereas the generic version is “thin-plate reptile.” Elasmosaurus aquatic reptiles were fossilized between 215 and 66 million years ago, during the late Triassic and late Cretaceous periods.

This group is well-known for possessing especially long necks, which are substantially longer, and overall bigger than those of the more common plesiosaurs. These lengthy necks are made up of several cervical vertebrae, including 71 in the Elasmosaurus. 


Elasmosaurus was approximately 30–34 feet in length, with a wide, flattened body and a comparatively short tail. It swam by flailing its flippers in the water in a rudimentary kind of underwater “flying,” similar to how sea lions do now. Mostly on the rear of the head, close to the eyes, were the nostrils.

Complete skeleton of a Elasmosaurus hanging off a ceiling in a museum
Complete skeleton of a Elasmosaurus hanging off a ceiling in a museum

Elasmosaurus may have fed by swinging its head back and forth because its neck was long but flexible. The skull of an Elasmosaurus would have been thin and triangular. Due to the fragmented nature of the fossils, it is unknown how many teeth Elasmosaurus had. However, the nose was curved but almost resembled a semicircle shape when seen from above.


Elasmosaurus was an apex predator and a carnivore. While they also ingested cephalopods, which are linked to modern squids and octopuses, it appears that fish made up a large portion of their diet. Despite being ambush predators, they glided and snatched their victim with their fang-like jaws. They may have eaten other marine invertebrates, and their usage of gastroliths likely helped them digest what they ate. Elasmosaurus’s long neck was essential to its eating strategy.

It would only be necessary for Elasmosaurus to float up to a school of fish, probably from underneath, so that it could conceal its bulk in the darker shade waters and then use its neck to lunge its head in and pull out a load of fish. Prey that was approaching from below, such as a school of fish, would similarly silhouette against the brighter surface water, rendering them simpler to distinguish and do away with their defense mechanism of light reflecting off of their shining scales.


The most likely place for Elasmosaurus to have existed was in the center of North America, which once held an old ocean that has now dried up. The ocean, which was shallow but nevertheless capable of covering a large portion of North America during the Cretaceous era, had once been located in the Midwest, where Kansas is currently located, close to the Western Interior Seaway.

Close-up on the skeleton head of a Elasmosaurus
Close-up on the skeleton head of a Elasmosaurus

These waters once reached a maximum depth of 2,700 – 3,000 ft and extended from the Rocky Mountains to the Appalachian Mountains. Due to the mushy, muddy consistency along the bottom, it’s plausible to assume that it was probably teeming with aquatic life, providing the Elasmosaurus enough creatures to feed.


Although there is presently no concrete proof that Elasmosaurus laid eggs on land or gave birth to live young, most researchers agree that it and other comparable aquatic reptiles would have done so. It is extremely unlikely that Elasmosaurus might have laid eggs on land due to the difficulty that it would have had just shifting its body if it ever found itself outside of the ocean and the precedent that is known to exist for all other marine reptiles like the ichthyosaurs as far back as the Triassic era. Today, it is also possible to see marine reptiles, such as sea snakes, giving birth to live offspring, proving that overall, reptiles are able to change to novel ways to survive in various habitats.


Being an apex predator, Elasmosaurus didn’t have any natural predators. At the end of the Cretaceous epoch, roughly 60–65 million years ago, this reptile is thought to have perished along with the other marine reptiles.

Vinyl recreated model of an Elasmosaurs
Vinyl recreated model of an Elasmosaurs

Shifting geographics, climate change has a direct impact on food availability, which leads some to believe that the reason why Elasmosaurus went extinct was because of the overall unavailability of suitable prey.

Facts about the Elasmosaurus

  1. Elasmosaurus fossils have served as the origin of the Loch Ness Monster myth.
  2. Elasmosaurus was unable to lift all of its head above the surface of the water.
  3. An entire extended family of aquatic reptiles bears the name Elasmosaurus.
  4. Elasmosaurus would, on average, measure 35 ft long and weigh 900 lbs.
  5. With 71 vertebrae, Elasmosaurus possessed the tallest neck of any Plesiosaur that has been discovered so far.


Why is Elasmosaurus not a dinosaur?

Elasmosaurus, like the majority of the swimming dinosaurs, wasn’t actually a dinosaur at all. It was a marine reptile, and It did indeed breathe. Because of how long their necks were, they had limited lift capability of the head over the water.

Is Elasmosaurus the biggest plesiosaur?

Elasmosaurus was among the largest plesiosaurs of the Mesozoic era, measuring nearly 50 feet long. Despite this, it was still no match for the heaviest members of the ichthyosaur, pliosaur, and mosasaur families of marine reptiles, a few of which would weigh up to 50 tons.

How did Elasmosaurus breathe?

Elasmosaurus and other marine reptiles occasionally had to surface for breath. They couldn’t survive underwater all the time since they lacked gills as fish and similar creatures do. Given its enormous lungs, it is not unlikely that a single breath from this aquatic reptile could sustain it for 10 to 20 minutes.

Can Elasmosaurus walk on land?

Elasmosaurus’ flipper bones were essentially rigid, making it impossible for them to be flexed into walking limbs. This prevents them from standing and walking comparatively as eared seals do.

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