Top 10 Largest Sea Dinosaurs Ever Discovered

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If you think that Sharks and Whales are the only sea monster ever alive on earth, then you are wrong. There were some sea monsters during the Triassic and Jurassic times that were so fearsome that they left behind shark by a quite good margin.

During the ancient time or age when there were Dinosaurs were ruling the planet Earth, there were some sea dinosaurs or monsters that used to feed on dinosaurs for food.

Some of these sea dinosaurs can grow up to 70 feet in length and 50 ton in weight.

So you can imagine that our seas and oceans are quite safe in respective of the ancient times. So let’s start our journey and get to know the top 10 largest sea dinosaurs ever discovered.

10. Styxosaurus

sea dinosaurs
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Styxosaurus was the large plesiosaur who belonged to the family of Elasmosauridae. It is believed that this sea dinosaur was from the Cretaceous period which means it was living on earth in between 66 to 146 million years ago.

According to the research and specimens found of this species, it is believed that this sea dinosaur was around 36 feet long and has a long neck. It neck can grow up to half of its body size and has 60 to 72 vertebrae.

In 1890 S.W. Wilson found the complete skull of Styxosaurus and from that a holotype specimen was made which had 20 vertebrae.

Later in 1945 another complete specimen of the species was discovered in Iona, South Dakota, US. This specimen indicated that these sea dinosaurs were quite big as expected before.

The above specimen is located in the Museum of Geology at the South Dakota School of Mines and Technology for public viewing.

largest sea dinosaurs
Image Credit: Wikipedia

This sea dinosaur had the sharp conical teeth which can be used for puncture and hold their victims. They used to swallow their food whole.

The above specimen which is located in Dakota was found with 253 gastroliths (stomach stones) in its abdomen. You can also see these stones if you visit the museum.

But Styxosaurus don’t use these stones for grinding of food, as other predators do during that time. Instead they use these stones as ballast because in one of the specimen which was found in the western Kansas there were fish bones found in its abdomen as well.

There food mostly includes fish, squids and belemnites.


9. Kronosaurus

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Kronosaurus was the short neck pilosaur which can grow up to 36 feet. Since it was among the largest pilosaurs that is the reason it was named after the Greek Titans leader, Kronos.

Remains of this species were discovered from Australia and Columbia. In 1899, a part of its head was found which has six conical teeth.

Later in 1977, a farmed in Columbia found the found a big stone which he later discovered as a bone and when the place was searched thoroughly, the full size specimen was found. The people of the village built the museum where the specimens were found and this whole sea dinosaur is available for public viewing.

These 100 million years old species were carnivorous and had large conical teeth. Some of its teeth turned into fangs. It had a huge skull of about 10 ft long and about 6.5 in width.

Fossils from the stomach of Kronosaurus, which was found in the Australia, Queensland Musuem, stated that he mostly fed on turtles and plesiosaurs.

According to the skull of Eromangasaurus found with round teeth marks on its neck suggested that these marks were from the teeth of Kronosaurus.


8. Albertonectes

biggest sea dinosaur
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Albertonectes is the longest and the only elasmosaur ever discovered. There is only single species of this sea dinosaur and was found by Tai Kubo, Mark T. Mitchell and Donald M. Henderson in Alberta, Canada.

This species is the longest neck sea dinosaur ever discovered. They have 23 feet long neck with a record 76 neck vertebrae. There has been no sea dinosaur with so much neck vertebrae.

This only specimen who was found in 2012 is located at Royal Tyrell Museum of Plaeontology in Drumheller, Alberta for public viewing. The holotype which was found is 37 feet long without the neck and if we include the neck it will be approximately 38 feet long.

It whole body has 132 vertebrae if calculated from head to the tail.

According to the National Geographic, Kubo and other author propose that the front position of the neck would have been broken because of the weight of the back body on the neck when this sea dinosaur fell down on the ground.


7. Thalassomedon

largest long neck sea dinosaur
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Thalassomedon is amongst the largest elasmosaurids with a total length of approximately 38 feet or can be more. They have long neck which was around 19 feet with 62 vertebrae.

This sea dinosaur used to live in Colorado, Nebraska and Kansas approximately 95 million years ago. It was discovered that the length of their neck used to increase as time passes so they might become as big as 45 feet long, according to the sources.

They mostly feed on small fishes. They were not very agile because of their long neck so they used to move their slowly from the dark without getting noticed by their victim and attack as their head reaches very close. They mostly attack from below of their victim because they have eyes on the upper part of their head.

Hunting from below of their prey may also have been used to hide their bigger part of their body in the dark of the oceans and reach their prey with the help of their neck.

Stones were found in their stomach which might help in the digestion of the food.


6. Elasmosaurus

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Elasmosaurus is like a brother to Albertonectes, but they can grow far bigger than them. It can grow up to 45 feet in length with a 23 feet long neck.

These sea dinosaurs were mostly found in some regions of North America approximately 93 million years ago. They were carnivorous and reproduced by live birth.

The first specimen of this creature was discovered in 1867 near Fort Wallace, Kansas, United States. From then on there were at least 10 discoveries till now of these species. It is believed that they have 72 neck vertebrae.

There was also one theory made by some researchers that they can grow up to 50 feet long and have a weight of 45 ton. This discovery was made according to the specimen found during Jurassic Period.

But this discovery was not believed because there was not much proof. Later according to the previous full size specimen it was stated that they were around 2 ton in weight.


5. Tylosaurus

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Tylosaurus was the one of the most fearsome hunter in the ancient seas. Like other sea dinosaurs it does not have a tooth which comes out of their jaw line. Their teeth were inside and only being seen when they opened their mouth.

They belong to the family of mosasaurs. They were so big that they swallow their prey whole in one gulp after catching.

They can grow up to 46 feet long and unlike other species in the same category that used them limbs to flow in water; they use their tail to move rapidly in water. They have long muscular, vertically flattened tail which increases their speed.

sea dinosaur skull
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According to the specimen found in their stomach they used to prey on fish, sea birds, sharks, mosasaurs and plesiosaurs for food.

Many remains of this dangerous ancient sea dinosaur have been found in Kansas, which was previously covered by the large ocean.  

According to the specimen found in Alaska it was discovered that they even feed on dinosaurs.


4. Pliosaurus

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Pliosaurus was the marine sea dinosaur who was alive during Late Jurassic Period in Europe and South America.

They might be on the top of the food chain because of their large size. They can grow up to 49 feet in length and weighted around 8 ton.

They have large teeth which were approximately 30 centimeters long and strong jaws which can any sea monster. They prey might include fish, plesiosaurs, ichthyosaurs, giant fish and other small pliosaurs.

There were numerous fossils that were discovered of this creature but the most notable was the fossils discovered from the island of Spitsbergen in the Svalbard archipelago. There were total of 20, 00 pieces that were discovered and when they were combined which took a long time; the outcome was the large pliosaurus which was named as “Predator X”.

Predator X became quite famous in news and on social media. It was also featured in the dinosaur documentary series named “Planet Dinosaur”.

According to some researches this creature can be bigger than 49 feet because some of its specimen indicates its weight around 30 to 50 ton.


3. Shonisaurus

sea dinosaur
Image Credit: Wikipedia

Shonisaurus belongs to the genus of ichthyosaur and was active during the Carnian age of late Triassic period. This means this creature was alive 230 million years ago.

The first incomplete fossils were found in Navada in 1920. There were around 37 incomplete fossil of this creature found in the Luning Formation of Nevada, USA.

According to the specimen discovered it was stated that they can grow up to 49 feet in length. They have long pointy narrow jaw line just like Dolphins. They have body just like shark but face just like a dolphin.

Since they don’t have many teeth because of their jaw line, they mostly feed on fish, ammonites and small marine reptiles.

Image Credit: Wikipedia

You can view the Nevada fossil sites at Berlin Ichthyosaur State Park.

Shonisaurus also became famous in pop culture and was one of the aquatic creatures in Jurassic Park Builder. It also appeared in Dinosaur train and documentary Sea Rex: Journey to the Prehistoric World.


2. Mosasaurus

largest sea dinosaur
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Mosasaurus was the ancient aquatic reptile a.k.a sea dinosaur which belongs to the genus of mosasaurs. This creature used to rule the sea during the Late Cretaceous period, nearly 80 million years ago.

The first fossils were found in the late 1700s near the Dutch city of Maastricht. After that there were numerous fossils discovered of this giant sea reptile in many states.

According to the research and interpretation of the fossils discovered it is estimated that this sea dinosaur can grow up to 58 feet in length.

biggest sea dinosaurs
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According to the dimensions by the Jurassic World, these sea monsters can weigh approximately 20 tons. They were 10 feet in width.

These prehistoric creatures were so large that they feed on Plesiosaurs and other dinosaurs for food. They can even kill a great white shark.

According to the large teeth marks of the fossils of the giant sea turtle, it was stated that this creature was so big that it can kill and feed on any other creature available in front of him.


1. Shastasaurus

largest sea dinosaur
Image Credit: Wikipedia

Shastasaurus which also come under the genus of ichthyosaur was the largest sea dinosaur ever discovered who used to live in ancient seas.

This prehistoric sea monster was alive used to rule the seas during Triassic periods. The remains of this creature were found in United States, China and Canada.

These species that were alive, approximately 200 million ago can grow up to 69 feet in length.

They have a huge skull with length approximately 10 percent of their whole body. But, despite having such an enormous body this sea monster does not have teeth in their jaws. It is believe for food they prefer suction feeding. This is main reason they could only feed on small fish and soft bodied cephalopods.

Some researchers also stated that their mouth does not fit the profile of suction feeding but it has not been proved yet.

Geetesh.S

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