An Ultimate Guide to Kronosaurus: The Lizard of Kronos

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NameKronosaurusDietCarnivorous
Name Meaning“Kronos Lizard”HeightN/A
PronunciationKroh-noh-SAWR-uhsLength9–10 meters (30–33 feet)
EraMesozoicEarly CretaceousWeight10.6–12.1 tons (23,400–26,700 lbs)
ClassificationSauropterygia, Plesiosauria & PliosauridaeLocationAustralia & South America

Kronosaurus Pictures

Kronosaurus was a marine reptile and one of the largest short-necked pliosaur of Cretaceous Seas
Kronosaurus was a marine reptile and one of the largest short-necked pliosaur of Early Cretaceous Seas | CoreyFord via iStock

The Kronosaurus

Gage Beasley Prehistoric's Kronosaurus Concept
Gage Beasley Prehistoric’s Kronosaurus Concept

Kronosaurus was a massive marine reptile that lived during the Early Cretaceous Period. 

It was a short-necked pliosaur, which means it was related to other marine reptiles of the Cretaceous Period, such as the Pliosaurus and Liopleurodon.

Kronosaurus lived in Australia between 121 and 105 million years ago. 

It was an apex predator that ruled the oceans and inland seas of the Cretaceous Period. 

The genus name translates as Kronos lizard or lizard of Kronos, and it was named after the Greek Titan, Kronos.

Kronosaurus is classified as a pliosaur, a group of short-necked plesiosaurs known for their massive size and powerful jaws
Kronosaurus is classified as a pliosaur, a group of short-necked plesiosaurs known for their massive size and powerful jaws | Trassnick via iStock

Although there are some disagreements about the actual size of this marine reptile, Kronosaurus was arguably the largest known pliosaurid. 

It was also one of the deadliest marine reptiles to have ever lived, with a bite force higher than that of the famous Tyrannosaurus rex. 

Unfortunately, scientists have only found a few fossils of this marine reptile, which has left questions about some aspects of its anatomy and behavioral attributes.

 In this article, we’ll discuss some of the known facts about this fascinating reptile. 

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

Physical Characteristics

Kronosaurus was a large, short-necked marine reptile. 

It is the largest of all its closest relatives in the pliosaur subfamily. 

This reptile had a massive and robust body, streamlined and fully adapted to a marine lifestyle. 

Gage Beasley Prehistoric's Kronosaurus Size Comparison Chart
Gage Beasley Prehistoric’s Kronosaurus Size Comparison Chart

The compact body of the Kronosaurus tapered towards both ends and was supported by abdominal ribs (also known as gastralia).

The ribs helped to keep the body firm. 

Like the other pliosaurs, the Kronosaurus’ head was quite massive. 

The skull length of this reptile was at least 2.4 meters and may have been as much as 2.7 meters.

Although there are disagreements about this reptile’s total length, estimates range from just eight meters to about 12 meters.  

Kronosaurus probably weighed between 10.6 and 12.1 tons 

Kronosaurus was named after the Greek titan Kronos, who was known for his immense strength and power
Kronosaurus was named after the Greek titan Kronos, who was known for his immense strength and power | Daniel Eskridge via iStock

Some estimates claim this marine reptile was more than 13 meters long, but this was probably exaggerated. 

The narrow, elongated skull of the Kronosaurus housed a set of cone-shaped teeth that interlocked when the jaws were closed. 

The teeth were a few inches long but weren’t very sharp. 

The Kronosaurus makes up for this by having a lethally powerful bite and a strong grip. 

The limbs of Kronosaurus were adapted from paddles similar to those of a turtle. 

The hindlimbs had a diameter of up to two meters and were slightly bigger than the forelimbs. 

It also had a short but well-developed tail which probably had a small fin, as seen in some plesiosaurs.

Habitat and Distribution

Kronosaurus is mainly known from fossils discovered in Australia. 

The fossils date back to the Late Cretaceous Period, specifically between 120 and 105 million years ago.

The limited fossil remains of this reptile suggest that it had a limited geographic range that was restricted to an inland sea known as the Eromanga Sea. 

This was a high-latitude inland sea that covered vast areas of inland Australia between 120 and 90 million years ago. 

The relatively shallow sea was frigidly cold, with conditions nearing freezing point. 

Some parts of this sea were probably covered by sheets of ice during certain seasons of the year. 

3D illustration of Kronosaurus under the sea
3D illustration of Kronosaurus under the sea | MR1805 via iStock

Although the most complete Kronosaurus fossils come from Australia, a few fragmentary fossils have been found in Colombia. 

Due to the distance between these two locations during the Cretaceous Period, experts think the Kronosaurus could have had a worldwide distribution across the various seas of the Mesozoic Era. 

Behavior and Diet

Kronosaurus was a powerful and efficient swimmer.

Its streamlined body, powerful swimming muscles, paddle-like limbs, and well-developed tail helped with locomotion through the water.  

Experts think it propelled itself through the water by undulating its entire body laterally while steering with the oversized flippers. 

This swimming technique is similar to that of modern-day crocodiles and other marine reptiles.

Kronosaurus attacks an extinct genus of large freshwater fish
Kronosaurus attacks an extinct genus of large freshwater fish | MR1805 via iStock

Kronosaurus didn’t live in large groups or exhibit other advanced social behavior. 

However, based on the presence of juvenile Kronosaurus fossils alongside adult specimens, experts think they exhibited some level of parental care. 

Kronosaurus offspring remained with their parents until they could fend for themselves. 

Kronosaurus was an apex predator that prowled the shallow Eromanga Sea for food. 

With large conical teeth that measured up to seven centimeters (2.8 inches) in length on average, this reptile was capable of taking down pretty much any animal in its ecosystem. 

The estimated bite force of this massive marine reptile was about 30,000 newtons. 

This is almost twice as powerful as the bite force of the saltwater crocodile. 

Kronosaurus distinctive feature was its massive head, which could reach up to 10 feet in length
Kronosaurus’s distinctive feature was its massive head, which could reach up to 10 feet in length | CoreyFord via iStock

The Kronosaurus’ teeth and massive jaws were capable of crushing the shells of the huge ammonites that lived in the Cretaceous waters. 

It also preyed on marine invertebrates such as giant squid, fish, and other contemporaneous marine reptiles that were smaller in size. 

Scientists have found fossils of an eight-meter-long plesiosaur called Eromangosaurus with possible bite marks from Kronosaurus on it. 

This shows just how varied the diet of the Kronosaurus must have been. 

To obtain food, Kronosaurus likely relied on its exceptional swimming abilities to pursue and capture prey. 

Once it catches up with prey, the Kronosaurus’ open and shut bitting was capable of grasping prey efficiently. 

But the narrow snout was poorly suited for twisting prey like crocodilians do. 

Life Cycle

3D illustration of Kronosaurus attacking a fish species
3D illustration of Kronosaurus attacking a fish species | MR1805 via iStock

Kronosaurus individuals reproduced sexually, with males and females coming together to produce young. 

Although they were reptiles, female Kronosaurus probably gave birth to live young. 

The young hatch from eggs carried in the mother’s belly—a condition known as ovoviviparity. 

So far, no conclusive evidence of live birth has been found for the Kronosaurus

But the size of this reptile and their lack of terrestrial adaptations would have made it difficult to come ashore to lay eggs. 

Scientists have evidence that shows that the ichthyosaur, another marine reptile that lived during the Cretaceous, reproduced by giving birth to live  young instead of laying eggs. 

It is likely Kronosaurus was adapted to live in the ocean like this too.

Beneath the ocean's depths, a gathering of Kronosaurus lurked while a pod of Dolichorhynchops darted away, seeking escape
Beneath the ocean’s depths, a gathering of Kronosaurus lurked while a pod of Dolichorhynchops darted away, seeking escape | CoreyFord via Getty Images

Juvenile Kronosaurus remained with their mothers for weeks or months after birth until they were old enough to hunt prey independently. 

Kronosaurus, like many reptiles, likely exhibited indeterminate growth, which means it continued to grow throughout its life.

As the juveniles grew, they would have experienced significant growth spurts, gradually increasing in size until they reached maturity. 

The growth rate may have slowed down after attaining maturity.

This indeterminate growth pattern allowed the Kronosaurus to grow to such a great size. 

Evolution and History

Kronosaurus belongs to a group of marine reptiles known as pliosaurs.

Side profile of kronosaurus in a white background
Side profile of kronosaurus in a white background | CoreyFord via iStock

Members of this reptilian group were part of a larger order called the Plesiosauria. 

Pliosaurs are characterized by their short neck, stocky build, and large head.  

This group of marine reptiles thrived during the Mesozoic Era, particularly the Jurassic and Cretaceous periods.

Plesiosaurs (pliosaurs and long-necked plesiosaurs) are secondarily marine. 

This means they evolved from terrestrial ancestors that returned to the ocean. 

The ancestors of the Kronosaurus and other plesiosaurs were sauropterygian reptiles that returned to the ocean in the Early Triassic Period. 

They were relatively smaller, with shorter necks and broader skulls but soon evolved into much bigger sizes. 

Kronosaurus was a powerful swimmer, capable of covering large distances in the open ocean
Kronosaurus was a powerful swimmer, capable of covering large distances in the open ocean | Trassnick via iStock

Most of these sauropterygian reptiles died off at the end of the Triassic Period, but some of them persisted into the Jurassic and Cretaceous periods. 

The evolution of large pliosaurs like the Kronosaurus can be traced back to the Jurassic Period. 

They developed large heads with massive jaws and short flexible necks that favored their prey-hunting lifestyle. 

They also developed large conical teeth, which were effective for catching and holding on to prey. 

The surface of the Kronosaurus’ teeth lacked the sharp edges (carinae) seen on the teeth of other large marine reptiles. 

This seemed like an adaptation for crushing prey with hard shells, such as the ammonites that were quite abundant in the Kronosaurus’ habitat. 

Interactions With Other Species

Kronosaurus with a marine reptile
Kronosaurus with a marine reptile | MR1805 via iStock

Given its size, Kronosaurus was undoubtedly a formidable predator. 

It was arguably the largest and deadliest animal in the Early Cretaceous seas. 

It was capable of preying on a variety of marine organisms, including fish, cephalopods, and marine reptiles. 

Kronosaurus likely faced competition from other marine reptiles present in the same ecosystem. 

There’s very limited evidence to fully explain the nature of their relationship with the other pliosaurs, but it likely involved competition for similar prey. 

Later in the Cretaceous, more agile, better-adapted marine predators such as the mosasaurs and prehistoric sharks emerged. 

These emerging marine predators outcompeted large pliosaurs like the Kronosaurus and replaced them as the apex species in the Late Cretaceous seas. 

Cultural Significance

3-image panorama of the kronosaurus
3-image panorama of the kronosaurus | Tim Sackton via Wikipedia CC BY-SA 2.0

Kronosaurus was the largest of the pliosaurids. 

As a result, it is considered an iconic reptile by scientists and the general public. 

Despite being such a crucial genus, fossils of Kronosaurus are relatively rare compared to those of other large Cretaceous reptiles.

However, several important fossils have been identified for this genus, and it remains one of Australia’s most popular prehistoric animals

Limited fossil remains have made it difficult to understand certain aspects of the Kronosaurus’ life, starting with its size. 

Some of the estimates and reconstructions of this dinosaur’s size were exaggerated. 

One reconstructed skeleton measured an impressive 12.8 meters in length, up to three meters over the agreed average length. 

Holotype mandibular symphysis fragment of kronosaurus
Holotype mandibular symphysis fragment of kronosaurus | Heber Longman via Wikipedia Public Domain

The inaccuracies apart, Kronosaurus has played a vital role in our understanding of the large pliosaurs and the prehistoric ecosystems where they lived. 

Actual fossils and reconstructions of the Kronosaurus are commonly displayed in museums and exhibitions, especially in Australia. 

The reptile is also commonly referenced in scientific books and documentaries, such as the 2003 BBC documentary series “Walking with Dinosaurs.” 

In this documentary, Kronosaurus is featured in an episode about “Sea Monsters” and is depicted as a ferocious predator capable of killing other marine reptiles.

Conclusion

Kronosaurus was a large marine reptile that plied the oceans of the Early Cretaceous Period. 

It is best known from fossils recovered from the Queensland area of Australia.

The region where the most prolific fossils of this reptile have been found was once covered by a shallow sea known as the Eromanga Sea. 

This inland sea which covered most of Australia about 120 million years ago, was the Kronosaurus’ home. 

However, experts think it may have had a worldwide distribution. 

With size estimates of up to 10 meters, the Kronosaurus was one of the largest pliosaurs ever found. 

Given its size, the Kronosaurus was an apex predator that snacked on fish, cephalopods, and other marine Invertebrates. 

Kronosaurus probably preyed on its own closest relatives as well. 

Little wonder this massive reptile was named after Kronos, the Greek Titan famous for eating his children. 

It is an iconic representation of the Early Cretaceous pliosaurs that demonstrates just how diverse the group was before they got wiped out. 

FAQS

Did Kronosaurus have any natural predators?

As an apex predator, Kronosaurus most likely didn’t have many natural predators in its marine ecosystem. 

It occupied the top of the food chain for most of the Early Cretaceous Period. 

However, juveniles and other vulnerable individuals may have fallen prey to other large marine reptiles. 

Where were the first Kronosaurus fossils found? 

The first officially recognized fossil of the Kronosaurus was discovered in a town called Hughenden in Queensland, Australia. 

The species, which was later named Kronosaurus queenslandicus, was discovered in 1899. 

How big were the Kronosaurus teeth?

Kronosaurus had an anisodont dentition which means the size and shape of their teeth varied. 

On average, their teeth were over seven centimeters (2.8 inches) in length. 

The longest of their teeth may have measured up to 30 centimeters (12 inches). 

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