
Elasmosaurus Was Not a Dinosaur
Elasmosaurus was a large marine reptile with an extremely long neck that lived in the ocean 65 million years ago. This group is not a dinosaur group, but is reptilian and belongs to the family group Plesiosauria. This genus had a snake-like neck and large wide body which resembled that of a turtle without its shell.
Quick Facts
Name | Elasmosaurus |
Prehistoric Era | Late Cretaceous |
Classification | Piscivore |
Order | Plesiosauria |
Suborder | Plesiosauroidea |
Weight | 2.2 short tons (2 tonnes) |
Length | 46 feet (14 meters) |
Height | – |
Maximum Speed | Unknown |
Territory | North America |
What Did Elasmosaurus Look Like?

Of the largest plesiosauri, at several tons, Elasmosaurus had four long paddle-like flippers, an extremely long neck (the longest of any Plesiosaur) topped with a tiny head, and a short tail (typically no longer than the flippers). Its neck accounts for half its total length. Imagine that where human beings have seven or eight vertebrae in their necks, Elasmosaurus had 75—76 vertebrae in its neck.
Plesiosaurs alike typically had broad bodies and short tails. Where the earliest Elasmosaurid were small, by the end of the Cretaceous Period their size had increased to a large as 46 feet (14 meters).
What Did Elasmosaurus Eat?
Elasmosaurus ate small bony fish, squid-like sea creatures, and mollusks. Gastroliths are found with Elasmosaurus remains, so it is possible that these were used as an aid in digestion. No one really knows if this would have been merely a side effect (of in fact using the stones for added weight in the larger bodies of ocean away from the coastlines).

Elasmosaurus ate fish and other swimming animals and shell‑less cephalopods. They had strong jaws and sharp teeth. Some Plesiosaurs have been found with small stones in their stomachs; these may have been used to help grind up their food, or as ballast, to help them dive.
The jaws of Elasmosaurus were probably quite strong—at least enough to bite through the large egg shells of its prey. If it is true that gastroliths were used in dietary aide and as a means of adding weight, then Elasmosaurus could have been a bottom-feeder as well.
How Did Elasmosaurus Move?
The extremely long neck of Elasmosaurus was key to its survival in the ocean. However, in contrast to what most would think, its neck was much less about reaching up out of the sea for food, and much more for stable buoyancy while swimming in the sea.
Elasmosaurus swam slowly using its four paddle-like flippers in a manner similar to that of modern turtles. It may have been able to move a little bit on sandy shores, perhaps to lay its eggs.
Contrary to popular misconception, Elasmosaurus (as any Plesiosaur) was not capable of raising its long neck above water, unless it were near a shore and could rest its body upon land for leverage. Primarily, Elasmosaurus would move about in the deeper waters. It is believed that this genus would have exhibited a quite capable prowess beneath the sea, with its four flippers—a characteristic plesiosauri trait that is not exhibited by any modern animal.
Where Did Elasmosaurus Live?
This genus lived during the Late Cretaceous Period and became extinct during the K-T mass extinction approximately 65 million years ago. The oceans were the habitat for Elasmosaurus.
During the Late Cretaceous Period when Elasmosaurus paddled the earth, the Western Interior Sea sat upon the land of what is today known as North America. Instead of the dry, flat land that exists today in the area, during the time of Elasmosaurus it was a land of swampy marsh areas and shallow seas. 70 million years ago, Elasmosaurus swam over what is now brick and mortar home to many people. In fact, this could by why today we find so many well-preserved dinosaur and other prehistoric animal remains. The environment’s role in fossilization is crucial in actual preservation. The best way to fossilize is to be covered (buried) at the bottom of a body of water where it is covered with tons of sediment. This type of covered environment is necessary to prevent scavenging and scattering. Over time, the sedimentary deposits at river-mouths and at the bottom of the sea build up more and more, adding needed cover and pressurization to form fossils.

The Discovery of Elasmosaurus
Elasmosaurus was named by paleontologist E. D. Cope in 1868 (from a fossil was found in Wyoming, USA). Other Elasmosaurus fossils have also been found in North America, in the Campanian Era Upper Cretaceous Pierre Shale of western Kansas, east of the Rocky Mountains in the Great Plains from Canada’s Pembina Valley to New Mexico. This area was previously covered in sea-water and frequented by many prehistoric animals.
Remains of Elasmosaurus are found in the area’s fossiliferous dark-gray shale which has lines of gypsum running throughout. The Pierre Shale is of marine origin and lied at the bottom of the Western Interior Seaway. This area of shale is related to other marine shales that exist farther west, such as the Bearpaw Shale, Mancos Shale and the Lewis Shale, along with the Lea Park Formation in central Alberta, Canada.
In the same Pierre deposits, such discoveries as the Late Cretaceous Lamniform Shark have been found, ichthyosaur, vertebrae of Mosasaur, along with many invertebrate fossils of ammonites, corals, baculites (such as cephalopod), gastropods, shrimp, snails, sea urchins and inoceramus clams.
Elasmosaurus Gave Live Births
For years it was assumed that the smaller plesiosaurs would have been land-bound enough to have laid their eggs upon sandy beaches much like modern Reptilia. However, scientists now realize that plesiosaur gave birth to live young. It is believed that after birth, plesiosaur would behave as modern whales regarding parental care of birthed young.
The Significance of Elasmosaurus—Heads or Tails?
Elasmosaurus has been fundamental in showing that we never completely know something, just because we have “found” it.
First, what were thought to be egg-bearers were in fact live-bearers (Elasmosaurus among them) and also that the long part of Elasmosaurus was not the tail, but the head. (Originally, when Elasmosaurus was first discovered and reassembled, scientists mistook the extra-long neck of Elasmosaurus as its tail, and reconstructed it as such, with the head on the tail end of the body.)
It takes much time and study by enthusiasts-turned-professionals who are willing to continuously extrapolate and build upon evidences found. In the case of Elasmosaurus, this type of professional attitude was largely compromised when one particularly over-the board and uncouth fossil-finder so publicly pointed out an original finder’s “error” in the placement of the Elasmosaurus head.
The original builder of the fossils of Elasmosaurus had gone so far as to publish in scientific journals, and upon learning his own error, went about retracting any of his original theories. It was too late. The unprofessional and humiliating black marketing tactics of his new rival had essentially instigated a war of production that would last well over twenty years. Known as the “Bone Wars”, the result was many new finds, along with much trickery, theft and bribery among over-zealous fossil-finders.
While the questionable business of recovering and selling dinosaur bones was already beginning to see the failings of competitiveness, the Elasmosaurus Fiasco heightened the problem to a degree that caused many to question the necessary ethics of such operations. The Bone Wars ran on much longer than their twenty year official recognition, affecting international views of American moral code and an entire industry not just those involved in the Elasmosaurus fiasco.