An Ultimate Guide to Elasmosaurus: The Plate Lizard

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Name Meaning“Thin Plate Lizard”HeightN/A
Pronunciationih-LAZ-moh-SAW-rusLength13 meters (45 feet)
EraMesozoicLate CretaceousWeight8 to 10 tons (16,000-20,000 lbs)
ClassificationSauropterygia, Plesiosauria & ElasmosauridaeLocationUnited States & Canada

Elasmosaurus Pictures

elasmosaurus pictures
Elasmosaurus | Warpaintcobra via Getty Images

The Elasmosaurus

Gage Beasley Prehistoric's Elasmosaurus Concept
Gage Beasley Prehistoric’s Elasmosaurus Concept

Elasmosaurus was a marine reptile species that inhabited the waters that formerly enveloped our planet’s surface during the Late Cretaceous.

Famed paleontologist Edward Drinker Cope made the first discovery in 1868, sparking a lifelong interest among scientists and paleoenthusiasts while also revealing crucial insights into Earth’s distant past.

During their “Bone Wars” dispute, paleontologist Othniel Charles Marsh made a spectacle of the fact that Cope had mistakenly placed the head of Elasmosaurus at the very tip of the tail.

Cope’s 1869 reconstruction of Elasmosaurus above, with head on the wrong end and no hind-limbs | Photo via Biodiversity Heritage Library

With the assistance of this comprehensive guide, we investigate the intriguing world of Elasmosaurus and reveal its significant paleontological relevance and ecological importance within the context of the Late Cretaceous.

Let’s delve into the complexities of this unique “Plate Lizard” to better appreciate the wonders of our planet’s old marine settings by looking at its evolutionary relationships, possible habits, and connections to the rich era of prehistoric life.

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

Physical Characteristics

Elasmosaurus | Daniel Eskridge via Getty Images

The marine lizard genus Elasmosaurus thrived exceptionally effectively throughout the Late Cretaceous.

Elasmosaurus is mostly known through fossilized bones, however, the physical characteristics of this marine reptile may be inferred from that of other elasmosaurids.

Elasmosaurus had a short tail, a tiny head for its size, a neck that was around 7.1 meters (23 feet) long, and lengthy paddle-like limbs.

Some of the largest necks and highest numbers of neck vertebrae ever recorded were found in the Elasmosaurus and its near sibling Albertonectes.

Contrary to popular belief, Elasmosaurus did not possess exceptionally long vertebrae in its neck.

Instead, it has a larger number of vertebrae, which results in its extraordinarily long neck.

Elasmosaurus stood out among plesiosaurs due to its unusually large number of 72 neck vertebrae.

Reconstructed skull and neck, North American Museum of Ancient Life | Zach Tirrell via Flickr (CC BY-SA 2.0)

It is even probable that it had more than that, as more vertebrae may have been destroyed or damaged by weathering or excavation.

The only other plesiosaur with a larger number of neck vertebrae than 70 is Albertonectes, with 75; having more than 60 vertebrae is considered to be highly advanced among plesiosaurs.

To put this distinctive trait in context, the giraffe poses the longest neck in the modern animal kingdom.

It can reach more than 2 meters (8 feet), yet have the same seven vertebrae that humans have, except each one is 10 inches long in a giraffe.

If the Elasmosaurus had extended vertebrae like giraffes, it would only have about 24 vertebrae in its long neck.

Despite having more vertebrae in their necks than even the longest-necked sauropod dinosaurs, elasmosaurids’ necks were much shorter overall.

Gage Beasley Prehistoric's Elasmosaurus Concept
Gage Beasley Prehistoric’s Elasmosaurus Concept

In 1869, Edward Drinker Cope estimated Elasmosaurus’ length at 13,1 meters (43 ft) by summing vertebral lengths and extrapolating missing portions.

Because cartilage was seen between the vertebrae in a living specimen, he calculated that the animal would have been around 13.7 meters (45 feet) in length.

American paleontologist Samuel Welles, on the other hand, projected the creature’s length to be 10.3 meters (34 feet) in 1952.

Elasmosaurus’ prolonged, triangular head tapered to a rounder snout that, when looked from above, virtually formed a semicircle.

Without complete fossils, we can only guess how many teeth Elasmosaurus had, but we may safely assume that it had six enormous fang-like teeth in each premaxilla.

Elasmosaurus Skull | dgero via Getty Images

Elasmosaurus stood apart from other plesiosaurus due to the higher amount of premaxillary teeth it sported.

The elasmosaurids have a heterodont tooth structure, suggesting that the size of their teeth varied from front to back.

The maxillae (upper jaw) normally had 14 teeth, whereas the dentaries (lower jaw) had 17 to 19.

Deductions about the lack of the holotype specimen’s pectoral and pelvic girdles have been derived from the initial descriptions and photographs from the late 19th century, even though their absence was noted as early as 1906. 

The middle bar was not distinguishable at the point where the scapulae (shoulder blades) had joined.

These broad, long shoulder blades have long “necks” and a large “upper process.”

Reconstructed skeleton, Centennial Centre for Interdisciplinary Science | IQRemix via Flickr

The girdle of the pectorals has a long bar through the middle, an apparently mature feature presumably absent in juvenile plesiosaurs. 

Midline fusion of the pelvic bones called ischia produced a medial bar that extended the full length of the pelvis.

For plesiosaurs, this is a quite peculiar physical feature.

Long paddlelike fingers were likely an adaptation for Elasmosaurus, as they were for other elasmosaurids and plesiosaurs in general.

In contrast to the longer pectoral paddles in the front, the pelvic paddles were noticeably shorter.

Habitat and Distribution

Elasmosaurus lived in the waters between 80 and 65 million years ago, throughout the Late Cretaceous.

Its range included the Western Interior Seaway, an enormous expanse of water that once divided the eastern and western halves of what currently constitutes North America.

As the Cretaceous period drew to a close, high temperatures and a thriving marine environment set in.

The Western Interior Seaway was a coastal, estuarine, open-water ocean ecology with a moderate marine depth.

A school of fish swims for safety when an Elasmosaurus shows up on the reef | CoreyFord via Getty Images

Conditions in this region, which ranged from the tropics to the subtropics, were characterized by warm water and plenty of sunshine.

Late Cretaceous oceanic ecosystems were rife with life.

Elasmosaurus coexisted with a diversity of marine organisms, such as marine reptiles like mosasaurs, turtles, and fish.

The waters were teeming with invertebrates, including ammonites, belemnites, and a variety of mollusks.

In addition, the Western Interior Seaway supported a wide variety of planktonic creatures, which provided an essential food source for numerous aquatic creatures.

Behavior and Diet

Elasmosaurus | Warpaintcobra via Getty Images

Elasmosaurids, such as the eponymous Elasmosaurus, were superbly suited to life in the sea.

They were built for constant swimming in the water, with sleek bodies and paddle-like limbs.

But their unusual anatomy made them slow swimmers, and their paddles probably operated like rowing oars, remaining inflexible with no ability for rotation.

Cope, back in 1869, likened the Elasmosaurus to a snake due to its reptilian features and behavior.

Because of the lack of space between the vertebrae and the extended neural spines, he concluded that Elasmosaurus’ trunk, or central physique, had restricted its ability to move vertically.

He reasoned, nevertheless, that the neck and tail would have been a lot less rigid.

Elasmosaurus | spyder24 via Getty Images

Recent studies have cast doubt on the long-held belief that Elasmosaurus could fully emerge from the ocean.

The center of gravity was not where previously thought; new evidence suggests that the animal’s long neck contributed to this. 

Only at mild to shallow depths, where it was able to lay its whole body on the ocean floor, did Elasmosaurus elevate its head and neck above the water’s surface.

Elasmosaurus presumably could not elevate its head and neck to a great extent due to the sheer weight of its neck, its lack of muscular mass, and its vertebrae’s limited range of mobility.

The Elasmosaurus, a carnivore, was a formidable predator in its day.

An Elasmosaurus marine reptile hunts a school of fish in Cretaceous seas | CoreyFord via Getty Images

Cephalopods (which have been traced to modern squids and octopuses) and fish (like Pachyrhizodus, Enchodus, and Cimolichthys) likely made up the majority of their food supply.

They sneaked up and snatched their victim with sharp teeth like fangs.

To better break down the aquatic life in their diet, they likely employed gastroliths. 

Elasmosauruses’ long necks were essential to their eating strategies.

Elasmosaurus could sneak up on a school of fish from below, where its large size would be concealed by the darkened waters, and then use its long neck to strike and bring in out a harvest.

Life Cycle

2 Elasmosaurus | MR1805 via Getty Images

In general, reptiles are oviparous, and it was believed until the turn of the 20th century that plesiosaurs would have laid their eggs on land or beaches like modern turtles.

Their robust limbs and flat stomachs gave the impression that they were capable of doing so. 

Since plesiosaurs’ forelimbs lacked functioning elbow or knee joints and the flatness of the underside would have caused a large lot of abrasion, it was hypothesized as early as the 19th century that they were viviparous.

It was also difficult to imagine how bigger species, nearly as big as whales, could have endured a beaching. 

The live delivery of offspring by plesiosaurs like Elasmosaurus was proven by an important fossil found in 1987.

Polycotylus latipinnis specimen (LACM 129639) containing a fetus on display at the Natural History Museum of Los Angeles County. | Jonathan Chen via Wikipedia (CC BY-SA 4.0)

The discovery of a pregnant Polycotylus latippinus in the fossil record raises the possibility that these creatures, like contemporary whales, showed parental care for their offspring.

The juvenile plesiosaur was around 1.5 meters (five feet) in length, while its mother was about five meters (sixteen feet) in length. 

This fits with the K-strategy for reproduction, where fewer children are born but more care is given to each one.

The development rates of plesiosaurs and the existence of sexual dimorphism (a variation in appearance between the sexes) are poorly understood.

This finding elucidates new details regarding the reproductive behaviors and lifespan of plesiosaurs, which contribute to our comprehension of their evolutionary success.

Evolution and History

Elasmosaurus on the hunt | MR1805 via Getty Images

Elasmosaurus is a member of the plesiosaur family, a diverse and successful group of aquatic reptiles that existed in prehistoric seas.

After diverging from more basic reptiles, plesiosaurs eventually became specialized for life in the water.

Elasmosaurus is related to other plesiosaurs known as elasmosaurids, which are distinguished by their long necks and sleek bodies.

The morphology of these aquatic reptiles changed considerably throughout time.

Elasmosaurus and its kin expanded their range of motion and food options by increasing the number of cervical vertebrae in their necks, making them more agile and predatory in the water.

Elasmosaurids, like Elasmosaurus, filled a number of ecological niches during the course of their development.

Elasmosaurus platyurus in the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado | MCDinosaurhunter via Wikipedia (CC BY-SA 3.0)

As top marine predators during the Late Cretaceous, they helped keep the marine food web in check by feasting on lesser marine species.

They had long paddle-like appendages and streamlined physiques, making them excellent swimmers and predators.

The fossil record reveals significant morphological, behavioral, and ecological function changes over time.

Alterations in body size, head form, tooth morphology, and feeding techniques are all possibilities.

A deeper understanding of Elasmosaurus’s evolutionary history, including how the species has responded to shifting environments and interacted with other species, may be gained by examining these alterations.

Interactions with Other Species

Outdated restoration of Elasmosaurus showing its neck raised above water, by Williston, 1914 | Photo via Water reptiles of the past and present

As the dominant marine predator during the Late Cretaceous, Elasmosaurus interacted with numerous other organisms.

It probably fed on fish, cephalopods, and ammonites, which were all small aquatic creatures.

Both mosasaurs and sharks were large marine reptiles that could have competed for sustenance.

Different aquatic species render 3D | Denis-Art via Getty Images

Elasmosaurus may have felt duress from other predators, such as Tylosaurus or Cretoxyrhina.

Additionally, symbiotic relationships between Elasmosaurus and other organisms are possible, but examples are presently undocumented.

These connections contributed to the preservation of the delicate balance of the ancient marine environment.

Cultural Significance

Computer generated 3D illustration with the prehistoric Plesiosaur Elasmosaurus | MR1805 via Getty Images

Elasmosaurus has historically and culturally significant characteristics due to its influence on popular culture and scientific research.

Due to its immense size and peculiar appearance, the sea lizard Elasmosaurus has captivated people all over the globe.

Elasmosaurus and other sea creatures of its genus have frequently appeared in folklore.

The lengthy necks and serpentine-like necks of these creatures may have provided inspiration for mythological sea serpents.

The Loch Ness Monster, or Nessie, as she is commonly known, has been likened in popular culture to a prehistoric marine reptile with a long neck, such as Elasmosaurus.

Loch Ness | Max2611 via Getty Images

These reports have only increased the mystique and allure surrounding these ancient aquatic reptiles.

Elasmosaurus has been essential to our scientific understanding of prehistoric existence.

Fossils of Elasmosaurus and other Late Cretaceous marine reptiles have cast a spotlight on the wide range and biodiversity of these creatures.

Paleontologists have gained a better understanding of the factors that drove evolution and ecology many millions of years ago because of the data gleaned from examining extinct species.


Elasmosaurus is a notable marine reptile with notable characteristics and ecological value.

A fossil of a pregnant individual proved that similar to contemporary whales, it gave birth to live young, along with the different kinds of its genus.

Its kind has also contributed to the legend of Nessie and inspired accounts of sea creatures. Elasmosaurus provides vital insights into ancient marine ecosystems and aids our scientific understanding of the diversity of prehistoric life.

Its study continues to expand our understanding of the past, and it remains pertinent to our ongoing investigation into the history of Earth.


Did Elasmosaurus really eat stones and pebbles?

Yes,  Elasmosaurus did eat stones and pebbles.

These stones are called gastroliths, which literally mean “stomach rocks”.

Scientists have theorized that this helped in digestion and buoyancy.

Is the Elasmosaurus a dinosaur?

Marine reptiles, such as Elasmosaurus, are known as plesiosaurs.

Although they coexisted with numerous dinosaurs, marine reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs weren’t dinosaurs. 

How did the Elasmosaurus die off?

The Cretaceous–Paleogene extinction event caused the extinction of plesiosaurs such as Elasmosaurus approximately 66 million years ago.


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