Last updated: October 30, 2022
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The hainosaurus was named after the Hainaut province of Belgium where the first specimen was discovered.

Hainosaurus Scientific Classification


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Hainosaurus Conservation Status

Hainosaurus Locations

Hainosaurus Locations

Hainosaurus Facts

Fun Fact
The hainosaurus was named after the Hainaut province of Belgium where the first specimen was discovered.

Hainosaurus Physical Characteristics

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The hainosaurus is an extinct genus of marine reptiles that were one of the largest members of the mosasaur family. They were around from the Campanian to the Maastrichtian age during the Cretaceous Period around 85 to 60 million years ago, in the oceans of Europe and Asia. The hainosaurus was a carnivore and top predator at the time. They went against very few threats and challenges due to its large size and ferocious nature.

Description & Size

The hainosaurus is an extinct genus of marine reptiles that were one of the largest members of the mosasaur family.

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At first discovery, the hainosaurus seemed larger. After further review, they only reached a length of 40 to 45 feet in size according to new scientific research. Still quite big but not as large as first thought. This makes them one of the largest mosasaurs and marine predators. The group contains invertebrates that evolved from semi-aquatic and scaled reptiles (squamates).

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When the first fossil specimens were discovered, they were believed to be around 55 feet in size. However, the number slowly reduced over the years as new discoveries were made. The hainosaurus body is streamlined and slender. They are fast swimmer in their marine habitat, but their large size did not always guarantee it.

They did not have a dorsal fin. Their very strong neck connected to prominent pectoral muscles and helped them to catch their prey. The thick tail played a role in the weight. The tail made up around one-third of its total body size. The average weight of the hainosaurus was between 10 to 15 tons.

Diet – What Did The Hainosaurus Eat?

The hainosaurus was a strict carnivore and feared predator in the ocean. This large creature was at the top of the food chain before it went extinct. They likely preyed on large fish and sharks, or any other large marine organisms. Plesiosaurs were likely a meal for the hainosaurus. Some evidence suggests that juvenile hainosaurus may have eaten smaller animals like birds and even ammonites like other mosasaurs did.

The hainosaurus mostly hunted in the ocean. They could also catch birds and other flying creatures that hovered above the water by leaping out to catch it. They ate plesiosaurs, turtles, pliosaurs, sharks, squids, and probably smaller mosasaurs.

Habitat – When and Where It lived

The hainosaurus lived during the Campanian to the Maastrichtian age during the Cretaceous Period around 80 to 65 million years ago. During this age and period, the sea level rose and covered many of the coastal areas and the Cretaceous Period was the third and final period of the Mesozoic era that lasted the longest at around 79 million years.

The hainosaurus was mainly found in oceans close to Europe and Asia, and this carnivorous vertebrate lived in deep water just like other mosasaurs according to the scarcity of their fossils. It is highly unlikely that they spent its time in very deep waters due to its large size which would have made it difficult.

Threats And Predators

The hainosaurus had a strong and sturdy tail that they likely used to defend themselves against predators. It is unknown what threats and predators the hainosaurus may have faced, but larger predatory marine creatures could have preyed on the hainosaurus.

Discoveries and Fossils – Where It was Found

 The first hainosaurus discovery was in 1885 by Louis Dollo who was a Belgian scientist born in France. The fossil was located in a Ciply chalk quarry in Belgium. He worked with the evolution of species, including dinosaurs and vertebrates.

The fossil remains of the hainosaurus were nearly complete, except for a dorsal and lumbar vertebra which is why scientists theorize that the hainosaurus did not have a dorsal fin. The reason that the hainosaurus was first thought to be larger than they actually were was because of the absence of the spinal segments.

The spine of the hainosaurus was well preserved, along with its ribs, and pelvic and pectoral girdles. Many vertebrae called chevrons of the hainosaurus protected the blood vessels and nerves around the chevrons. The tail is slightly shorter and contains fewer vertebrae with chevrons. It is highly unlikely that the hainosaurus lacked chevrons as protection in their tails.

Louis Dollow made the discovery of the bones of the hainosaurus and they are now kept in the Royal Belgian Institute of Natural Sciences. Dollo has a hypothesis stating once an evolutionary change occurs, it is not reversible. This is Dollo’s law. He supervised the Iguanodon exhibits in the Royal Belgian Institute of Life Sciences and was an assistant naturalist. Aside from his discovery, Dollo also wrote several books on paleontology and zoology.

The owner of the hainosaurus fossils quarry did allow scientists to harvest all the bones and Dollo appreciated his generosity enough to name the discovery after him.

One of the hainosaurus fossils was misidentified, and in 2005 a paleontologist named Johan Lindgren believed that the Hainosaurus pembinensis was a species of Tylosaurus in 2010 paleontologists Michael Caldwell and Timon Bullard redescribed the specimen which belonged to another mosasaur.

Extinction – When Did It Die Out?

The hainosaurus went extinct roughly 80 to 65 million years ago after the Cretaceous Period. The extinction event happened 66 million years ago due to widespread chalk deposits.

During this period, the continents were in different positions, and the supercontinent Pangaea was drifting apart, which was still when the Tethys ocean separated the northern continent known as Laurasia from the southern continent known as Gondwana.

An asteroid could also be the cause for the hainosauruses extinction, taking out the dinosaurs millions of years ago.

Similar Animals to The Hainosaurus

The hainosaurus shared similarities with other large aquatic vertebrates. Some of the similar animals were even once mistaken to be a species of the hainosaurus.

  • Tylosaurus- Part of the mosasaur genus and was a large predatory marine reptile that was misidentified as a species of hainosaurus.
  • Mosasaurus- The largest species of mosasaur that lived in the ocean and reached a length of 10 to 50 feet.

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About the Author

I am a big animal lover that not only enjoys owning and getting to care for them, but also to write about them! I own many fish, along with shrimp, hamsters and a docile tarantula. Writing has become my passion and I am grateful to be able to write about the animals I love so dearly so that I can share my knowledge and expertise in the articles I write.

Hainosaurus FAQs (Frequently Asked Questions) 

When was the hainosaurus alive

The hainosaurus was alive during the Campanian and Maastrichtian age in the Cretaceous Period, which was around the Mesozoic era 80 to 65 million years ago. They are now extinct along with many other similar species.

How big was the hainosaurus

The hainosaurus reached a length of 40 to 45 feet and weighted between 10 to 15 ton, however some were likely larger than this, reaching around 49 feet in size. This makes them one of the largest mosasaurs and marine predators at the time. This creature was first believed to be larger because of missing vertebrae, but it was discovered that they were smaller than scientists previously thought.

What did the hainosaurus eat?

The hainosaurus was a feared carnivore that roamed the ocean. They preyed on large marine creatures, from squid, turtles, and sharks, to plesiosaurs, pleosaurs, and other smaller mosasaurs. It is possible that the hainosaurus could also leap out of the water to catch birds, much like other mosasaurs would.

Who discovered the hainosaurus?

The hainosaurus was discovered in 1885 by Louis Dollo in a Ciply chalk quarry in Belgium. The entire hainosaurus fossil and bones were well preserved and nearly complete, except for a missing dorsal fin and some spinal vertebrae which is why scientists thought the hainosaurus was larger than they actually were.

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  1. Wikipedia , Available here: https://en.wikipedia.org/wiki/Hainosaurus
  2. LiveScience , Available here: https://www.livescience.com/29231-cretaceous-period.html
  3. Scientific America , Available here: https://blogs.scientificamerican.com/tetrapod-zoology/gigantic-shark-toothed-hainosaurus/

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