Elasmosaurus platyurus is the only species that has been found in the genus Elasmosaurus. It is a spectacular species of marine reptile, therefore it was not a dinosaur although it came to cohabit with great amount of them, since it dates from the end of the Cretaceous.

The main characteristic of the Elasmosaurus was the extremely long neck it possessed. To get an idea of its impressive appearance, it would come to be like a giant snake piercing the body of a turtle.

In fact, it holds second place in the ranking of animals with the longest neck in history.

Basic information about the Elasmosaurus

The Elasmosaurus was a fairly large animal that lived in the sea. It is a marine reptile that lived at the same time as several dinosaurs, but in no case should it be confused with one. Reptiles and dinosaurs are closely related, but they have their own morphological differences.

How long is it? – The average length of this marine reptile was approximately 14 meters.
What is its height? – The average height of the Elasmosaurus was about 3 meters.
What is its weight? – It was a rather heavy reptile, weighing no more than 2 to 9 tons.
When did it live? – This marine reptile began to inhabit the Earth 80 million years ago and would have existed until 65 million years ago.
What is its order? – It is classified within the Order Plesiosauria.

The taxonomy of the Elasmosaurus

Kingdom Animalia > Filo Chordata > Superorder Sauropsida > Class Diapsida > Order Plesiosauria > Suborder Plesiosauroidea > Family Elasmosauridae > Genus Elasmosaurus

Within the genus Elasmosaurus only one species has been found, E. platyurus. The possibility of finding other species in the future cannot be ruled out. We will keep this section up to date with possible future findings.

The order: the plesiosaurs

The Elasmosaurus are classified within the order Plesiosauria. This is because it has the characteristics of the plesiosaurs. To know a little better how the Elasmosaurus were, we must have clear the characteristics and features that have the plesiosaurs.

Plesiosaurs first appeared in the early Jurassic period. They inhabited the Earth until what is known as the K-T (Cretaceous-Tertiary) extinction that marks the end of the Mesozoic era, also known by many as the era of the dinosaurs.

Plesiosaurs have been mistakenly referred to as marine dinosaurs on several occasions. These animals are now extinct, although some scientists believe that they can still be found in fairly deep sea areas where humans are not yet able to reach (but this is pure speculation).

Most of the plesiosaurs had a rather short tail and a really wide body. The limbs they had were four, and they were long fins driven by strong muscles attached to the bony plates that formed the pelvis and scapular girdle.

The funny thing about their fins is that they made the movement of flying, waving them up and down. In addition, typical plesiosaurs would have breathed oxygen directly from the air, i.e. they had lungs and would have had to come up for air.

As far as the reproduction of these marine reptiles is concerned, it is quite surprising, as the young were born directly alive. This is something really curious because generally reptiles used to deposit eggs and not live young, something more typical of mammals. It is a type of reproduction called “ovoviviparous”, that is, they lay eggs but they lodge them inside, and when they hatch they come out of the mother.

However, within the plesiosaurs there are two morphologically well differentiated groups:

Plesiosauridae. These had a really long neck and a rather small head. They used to be slow and fed on small marine animals.
Pliosauroidea. These had a short neck and a much larger head in proportion. They used to be fast and were dangerous marine predators. They fed on large prey.
As many may have deduced, the marine reptile we are talking about this time belongs to the first group. The Elasmosaurus had a long neck, typical of those belonging to the suborder Plesiosauridea.

Why were they called plesiosaurs?

Initially, specimens of plesiosaurs were discovered and they were characterized by their long necks. However, later on a link was found with several short-necked specimens. That is why the need arose to subdivide the Order Plesiosauria into two: Sub-order Pilosauroidea and Sub-order Plesiosauridea.

Those of the last suborder are those originally classified only within the Plesiosaurian Order and that is why the resemblance of the order to the suborder. This sometimes leads to confusion because the term “plesiosaurs” is often used to refer to both the order and the suborder.

The discovery of the plesiosaur dates back to 1605, when Richard Verstegen of Antwerp found remains of this reptile, although at that time he did not yet refer to them as plesiosaurs. During the following years, the remains of plesiosaurs were described again and found by various palaeontologists.

The meaning of plesiosaur is given in the 19th century, when they were not yet well known and not much more had been determined than vague descriptions and discovery of remains.

In 1821, Conybeare and Henry Thomas de la Beche investigated the collection of remains of Colonel Thomas James Birch and would have found the remains that would end up being called plesiosaurs.

To give the name, the Greek word plesios and saurus, with origin in Latin, was used. The word plesios means closer, while as it is well known, saurus means lizard.

At that time the Ichthyosaurus had been previously classified, and with the name plesiosaur they wanted to make it clear that they were more similar to the morphology of lizards.

More detailed description of the plesiosaur suborder

Knowing more about the two groups of plesiosaurs that there are, let’s see better about the characteristics of the suborder Plesiosauridea. Most, if not all, have almost certainly seen a snake and/or a turtle at some time in their lives or at least know what a snake and/or a turtle is.

Now, to get an idea of the general appearance of an Elasmosaurus, you have to put the snake inside the shell of the turtle and make it 20 times bigger. That’s what this incredible marine reptile would have looked like.

The plesiosaurs had a fairly short tail and a fairly wide body. At first most were land-based reptiles but some evolved their limbs into flippers and eventually lived in the sea.

They could live without problems in cold habitats, as they had a warm-blooded metabolism, similar to that of mammals.

While the pliosaurids were quite fast, those in the plesiosaurid group would have been very likely slow swimmers. Especially underwater (diving) they moved at low speed.

To feed they would have used their long necks which were not only very long but also quite flexible. They would have turned their necks in the direction of small unwary fish or cephalopods and eaten them.

It is not known whether they were able to bend their necks upwards, but it is known that even if they could have, they would never have been able to stick their necks out above the surface of the water.

The weight of their necks was too great, and if not for the inability to bend their necks upward, it would have been the effect of gravity that prevented them from doing so.

The reproduction of these specimens was very strange, for unlike the other marine reptiles that give birth to a lot of small baby eggs, the plesiosaur would have given birth to only one large living baby.

The adult plesiosaurs were about four metres long, while the young would have been an average of one and a half metres long.

Why did plesiosaurs become extinct?

The cause of the extinction of the plesiosaurs was the K-T extinction. This happened about 66 million years ago, and would have meant the disappearance of about 75% of biological species.

Perhaps one day the exact cause of the mass extinction of species will be known, although with the tools we have today it is an impossible mission.

This happened millions of years ago and the evidence we have is not enough to determine exactly.

In the absence of conclusive evidence, several hypotheses have emerged concerning this. The most accepted hypothesis today is that of the K/T impact. The K/T impact is named after the German who developed the theory, Kreide/Tertlär Grenze.

This theory is the one which has been popularly taken almost as a fact (which really remains a theory and not an absolute truth) that many dinosaurs and other animals (among them plesiosaurs) were extinguished by a meteor shower.

Description of Elasmosaurus

Knowing a little more about the characteristics of the group to which this marine reptile belongs, let’s talk about the characteristics of the Elasmosaurus.

Elasmosaurus were approximately 46 feet (14.1 meters) long and 4.9 feet (1.5 meters) high. It should also be mentioned that they were very heavy marine reptiles weighing approximately 2 tons. All this makes them one of the largest plesiosaurs that has ever existed.

Starting from the top of this animal, the first thing we would find would be its jaw. The teeth of this animal were shaped like a needle, so they were fragile. This prevented the Elasmosaurus from crushing the shells of the mollusks, but at least it could catch them when they were open for the purpose of feeding.

The jaw of this animal was divided into two parts that met at the tip, to be more specific between the fourth and fifth teeth.

Its skull was relatively small (like a snake’s) in size compared to the rest of its body. The skull and jaw of this reptile were pointed, thin and rather flattened.

In spite of being a rather slow marine reptile, this shape allowed it to have a much more hydrodynamic silhouette.

The huge neck it possessed was difficult to maintain, this is thanks to the fact that it has several extra bones inside. These extra bones would give the neck great stability while giving it great flexibility.

Its vertebrae were quite long but not very wide and had lateral longitudinal ridges. In the rest of the body it had about three pectoral vertebrae and in its tail it had at least eighteen vertebrae.

What is really impressive is that it had more than 72 vertebrae in its neck.

The adult specimens had a long bony rod in their scapular waist that the young specimens did not have. The length of the edges of the scapula was practically the same both in the joint with the coracoid and in the joint surface of the humerus.

The anterior area of the pelvis was composed of three almost straight edges dipping to the sides and front of the animal.

From all the above, what really marks the difference of an Elasmosaurus with the other species, is that it has six premaxillary teeth and a large number of cervical vertebrae, specifically 72. Most of its cousins had only 5 teeth in the premaxillary, although some had 9 or even more.

However, most plesiosaurs had less than 60 cervicals, except for Styxosaurus, Thalassomedon, Hydralmosaurus and of course Elasmosaurus.

However, the Elasmosaurus is the one that leads the ranking of plesiosaurs with more cervicals, since it is the only specimen of this genus that exceeds 70 cervicals. The pectoral rod possessed by the Elasmosaurus shows that it was a very advanced animal species in terms of evolution with respect to its relatives.

Why were they called Elasmosaurus?

The name of the Elasmosaurus refers to one of its main characteristics. In this case, it refers to the thin plates on its pelvic girdle. The Greek word elasmos means thin plate and saurus would mean lizard.

The name of this reptile would mean thin plate lizard. This meaning is somewhat ambiguous and so the term ribbon lizard is more commonly used.

When did the elasmosaurus live?

Many people would like to see a dinosaur with their own eyes, either by studying them deeply or just out of curiosity. Unfortunately, these giant animals have been left as part of the historical legacy.

Still, the closest thing to the dinosaurs are the reptiles themselves and the birds with which they were once confused. Reptiles and dinosaurs are closely related, and fortunately there are still reptiles living on Earth.

This is not the case of the Elasmosaurus, a marine reptile that began to inhabit the planet some 80 million years ago, and which became completely extinct in the event known as the great extinction and occurred some 66 million years ago.

As you can see, this aquatic reptile has come to live in the well-known era of the dinosaurs.

The time scale in which they inhabited is known as the Upper Cretaceous. This is the name given to the era that started 100.5 million years ago and ended with the great extinction (66 million years ago).

During the Upper Cretaceous, we could find dinosaurs of all kinds: ceratopsians, hadrosaurs, ankylosaurs, tyrannosaurs and many others. The first birds began to appear and mammals began to make a niche for themselves.

In the maritime terrain, there were large predators such as mosasaurs and plesiosaurs.

In the Upper Cretaceous, the continents were already separated and had a distribution similar to the present one. However, there were some parts quite different as the great sea that existed in the center of North America.

India was not yet united to the Eurasian continent, it was separating from Africa to finally collide with Asia in later times.

What did the Elasmosaurus feed on?

The Elasmosaurus was a slow swimmer and would most likely have stalked large schools of fish. To do so, it would have stood still under the shoal of fish and when they were passing over it, it would have slowly raised its head upwards.

It is very likely that its eyes had stereoscopic vision in order to identify small prey.

It is likely that by using this technique it would have been able to feed on small bony fish, ammonites (such as molluscs) and belemnites (an animal similar to the current squid). To facilitate digestion, it would have used small stones for a gastrolitic process.

Who discovered the elasmosaurus?

Edward Drinker Cope described Elasmosaurus platyurus in March 1868 with a fossil collected by Dr. Theophilos Turner (military doctor) from western Kansas (United States).

Many more specimens of Elasmosaurus have been found, although finally Carpentier in 1999 determined that only a single species of this genus existed.