An Ultimate Guide to Megalosaurus: The Great Lizard

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Name MeaningGreat LizardHeight1.8 to 2.2 meters (5.9 to 7.2 feet)
PronunciationMeg-ah-lo-sore-usLength9 m (29.5 feet)
EraMesozoic Middle JurassicWeight900 to 1,000 kilograms (1,984 to 2,204 pounds)
ClassificationDinosauria, Saurischia, TheropodaLocationEngland

Megalosaurus Pictures

Megalosaurus | Elenarts108 via iStock

The Megalosaurus

Gage Beasley Prehistoric's Megalosaurus Concept
Gage Beasley Prehistoric’s Megalosaurus Concept

The Megalosaurus is one of the most important dinosaur genera, as it was among the three that served as the basis for creating the Dinosauria clade.

As such, Megalosaurus fossils were among the first discovered and described dinosaur fossils.

When the first Megalosaurus fossils were discovered, no one even dared think they belonged to a dinosaur.

They were initially thought to have belonged to a fish, a war elephant, and even a biblical giant!

Contrary to popular belief, the Megalosaurus was not the oldest dinosaur, as it lived roughly 166 million years ago during the Middle Jurassic.

Computer-generated 3D illustration with the Dinosaur Megalosaurus
Computer-generated 3D illustration with the Dinosaur Megalosaurus | MR1805 via iStock

It was an inhabitant of today’s Europe and likely an apex predator in its habitat.

The Megalosaurus was a bipedal theropod and one of the largest theropods of the Middle Jurassic.

One distinctive feature of the genus is the unusually elongated head and the short, robust neck that supports it.

These are only some of the fascinating details we’ve discovered about the Megalosaurus!

If you want to learn more, keep reading!

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

The Megalosaurus was a typical theropod. It had a bipedal build, with short forelimbs and long hind limbs.

The tail was long, functioning as a counterbalance.

The head was unusually elongated and equipped with long, blade-like teeth.

The neck was short but unusually robust, built this way to support the large head.

The forelimbs bore three digits each and were quite robust, considering their size.

The hindlimbs had three toes each, which were facing forward.

Megalosaurus dinosaur roaring up isolated in white background
Megalosaurus dinosaur roaring up isolated in white background | Elenarts108 via iStock

It is believed that the Megalosaurus was among the largest theropods of the Middle Jurassic.

One fossilized femur belonging to this dinosaur measured 80.7 centimeters (31.8 inches) long.

Based on this number, scientists estimate a body mass for this specimen of approximately 943 kilograms (2,079 pounds).

However, another calculation based on a thigh bone 76 centimeters (29.9 inches) long yielded a weight of 1.1 metric tons (1.2 short tons).

As such, weight estimations haven’t been fully confirmed, as no complete skeleton has been found to further support these calculations.

This is valid for the length as well.

Gage Beasley Prehistoric’s Megalosaurus Size Comparison Chart

The Megalosaurus was initially thought to have grown up to nine meters (29.5 feet) long, although further calculations downsized the length to 6–7 meters (19.7-23 feet).

The height was estimated at 1.8-2.2 meters (5.9-7.2 feet) tall at the hips.

Either way, considering that the Megalosaurus was alive during the Bathonian stage of the Middle Jurassic, it was still among the world’s largest theropods.

Habitat and Distribution

The Megalosaurus has been historically thought to have had quite a wide distribution.

Can you imagine that fossil discoveries led to the naming of over 50 species in the genus?

When the Megalosaurus was described, it was among the few dinosaur forms known to humans, which is why many other fossils were attributed to the same genus.

Over the years, they were reassigned to other genera, and the distribution of the Megalosaurus became more restricted.

As such, we can now state that the Megalosaurus was an inhabitant of modern-day southern England.

Here are some localities that revealed true Megalosaurus fossils:

  • Caswell, Witney, and Oxfordshire
  • Taynton Limestone Formation, Oxfordshire
  • Possibly Chipping Norton Limestone Formation, Cotswolds, England
  • Possibly Ardley, Oxfordshire
  • Possibly France

When the Megalosaurus was alive, meaning approximately 166 million years ago, our planet was experiencing a cold period, the Middle Jurassic Cool Interval (MJCI), which started 174 million years ago.

In the Early Jurassic, the territory we now call England was part of the supercontinent Pangaea.

Megalosaurus dinosaur walking toward the ocean by sunset
Megalosaurus dinosaur walking toward the ocean by sunset | Elenarts108 via iStock

By the Middle Jurassic, however, this supercontinent had started breaking up and creating the two supercontinents known as Laurasia and Gondwana.

England was on the supercontinent of Laurasia.

At the time, most of Europe was an archipelago of islands surrounded by shallow seas.

As such, the Megalosaurus likely lived in a highly aquatic environment, which is further proved by the fact that Middle Jurassic marine life peaked in terms of diversity.

Conifers, cycads, ferns, and ginkgoes probably dominated terrestrial ecosystems.

Behavior and Diet

Computer-generated 3D illustration with the Dinosaur Megalosaurus
Computer-generated 3D illustration with the Dinosaur Megalosaurus | MR1805 via iStock

The Megalosaurus was a bipedal carnivore and probably an apex predator in its habitat.

It was initially thought to have been a semiaquatic amphibian that spent time swimming and walking on land.

Over the years, however, and upon further discoveries, the Megalosaurus was confirmed to have been a higher-level reptile alongside the Iguanodon and Hylaeosaurus.

Scientists also suspected it had a high metabolism and an upright stance.

Like many other theropods, the Megalosaurus was a carnivore.

Its blade-like teeth were undoubtedly of great help in tearing prey apart.

But how often did the Megalosaurus actively hunt terrestrial prey?

Scientists haven’t yet been able to confirm this.

Battle between a Megalosaurus and an Iguanodon
Battle between a Megalosaurus and an Iguanodon | ZU_09 via iStock

Fossilized tracks associated with megalosaurids show that these dinosaurs likely walked to the coast when the tide retreated.

This indicates they may have been scavengers looking for dead marine creatures revealed by the retreating tide.

Some scientists believe that the Megalosaurus was piscivorous, but this hasn’t been fully confirmed yet.

Life Cycle

The reproductive behavior and life cycle of the Megalosaurus remain poorly studied because no fossilized nests, eggs, or complete juvenile skeletons were recovered.

We can, however, hypothesize how it reproduced based on the details known about dinosaurs.

Theropods reproduced by laying eggs, which is typical of all dinosaurs and modern birds.

Megalosaurus with its predecessor Velociraptor in a single image
Megalosaurus with its predecessor Velociraptor in a single image | MR1805 via iStock

Females laid two eggs at a time because they had two paired ovaries and oviducts.

The eggs were laid in clutches in nests built beforehand, either by the female or the male.

While it is believed that at least some theropods incubated the eggs, we cannot confirm this behavior for the Megalosaurus.

But if it did occur, the incubation likely lasted approximately 60–90 days.

Many baby dinosaurs were precocial.

This means they hatched quite developed, could fend for themselves, and did not require much adult help.

It remains unknown whether Megalosaurus hatchlings were precocial.

Evolution and History

Megalosaurus fossil
Megalosaurus fossil | Ballista via Wikipedia CC BY-SA 3.0

Fossils associated with the Megalosaurus were once thought to have belonged to a fish, a Roman war elephant, or an amphibian.

The earliest fossil was discovered in the 17th century, when the Taynton Limestone Formation revealed the lower part of a femur thought to have belonged to an unusually large creature.

It was initially associated with a Roman war elephant.

Another more plausible theory appeared sometime later: it was, in fact, the femur of a giant human.

As such, the fossil was called Scrotum humanum, as it looked like human testicles.

This discovery, which occurred in 1677, was followed by another major one in 1699.

Vintage engraving from 1883 of a Megalosaurus Jaw Bone | duncan1890 via iStock

The discovery of a mysterious tooth, then thought to have belonged to a fish but later associated with the Megalosaurus.

Another essential discovery bears the name of William Buckland, who acquired some of the most iconic bones that served as a basis for describing the genus.

They had been recovered from the Stonesfield quarry and were thought to have belonged to giant tetrapods.

Buckland concluded they did indeed belong to a giant creature that looked like a lizard, so they named the genus Megalosaurus. It was a lizard genus.

Although the dinosaur term was not yet known and these creatures were considered lizard-like reptiles, the Megalosaurus is now recognized as the first named non-avian dinosaur genus.

William Buckland was also the first to reconstruct a Megalosaurus.

He made it a quadrupedal amphibian with a semiaquatic lifestyle.

Its physiology was adapted for both swimming and walking on land.

In the context of Christian orthodoxy, he claimed that this giant creature had a beneficial role in the ecosystem of its time as it killed old and ill animals, thus diminishing animal suffering.

Megalosaurus, a genus of extinct meat-eating dinosaurs
Megalosaurus, a genus of extinct meat-eating dinosaurs | Mark Garlick via GettyImages

Upon further discoveries, the Megalosaurus and the other two discovered reptile genera, Iguanodon and Hylaeosaurus, were upgraded to a higher level; they now had an upright stance, a high metabolism, and were terrestrial creatures.

As such, in 1842, their description led to the creation of Dinosauria, which included only these three genera.

Ten years later, an English sculptor and natural history artist built a life-sized Megalosaurus model.

It was mounted at Crystal Palace Park, reconstructed as a mammal-like quadruped that featured a hump on the shoulder.

Nevertheless, this model is still on display at Crystal Palace Park and, despite its misleading characteristics, is one of the first models that made prehistoric wildlife known to the public.

Side view of Megalosaurus
Side view of Megalosaurus | Dorling Kindersley via GettyImages

Over the years, the Megalosaurus was associated with numerous fossils, primarily because scientists didn’t know any other dinosaurs besides the three genera in the Dinosauria group.

However, further findings led to the naming of a myriad of other dinosaur groups and genera, which, in turn, caused these fossils to be reassigned.

Today, the Megalosaurus genus consists of only one recognized species, Megalosaurus bucklandii.

Interactions with Other Species

Another theropod the Megalosaurus may have shared its habitat with is the Iliosuchus.

The thing is, some scientists consider it synonymous with the Megalosaurus, as the material associated with the genus is highly fragmentary and incomplete, thus not enough to distinguish it from the Megalosaurus.

Apart from this, no other dinosaurs have been discovered in the Taynton Limestone Formation.

Instead, the territory was home to the Klobiodon, a rhamphorhynchid pterosaur, the Teleosaurus, a crocodyliform, and various mammaliamorphs.

Head study of megalosaurus
Head study of megalosaurus | Mark Garlick via GettyImages

One of the most renowned mammaliamorphs living in the area is the Stereognathus.

Since the territory was a coastal environment, it was rich in fish.

Despite that, the Megalosaurus may have never crossed paths with it if we do not consider the possibility of it being a piscivorous dinosaur.

What about the famous descriptions that show the Megalosaurus feeding on the Iguanodon?

Well, these probably appeared before the publication of extensive studies on both genera that revealed that the two lived in different periods.

Other sources list that the Megalosaurus lived in the same habitat as the Cruxicheiros, another theropod.

If the Megalosaurus lived in France (which is a possibility), this theory may be approved.

Megalosaurus in the wild
Megalosaurus in the wild | Roger Harris via GettyImages

Another possible dinosaur that the Megalosaurus crossed paths with is the Cardiodon, a sauropod discovered in England’s Forest Marble Formation.

Although this formation did not reveal any Megalosaurus fossils, we cannot rule out the possibility that it reached this territory.

The Ceiosauriscus may have also coexisted with the Megalosaurus, as its fossils were recovered from various locations in England.

Cultural Significance

After this comprehensive description of the genus and going through the discovery history of Megalosaurus fossils, we don’t even have to mention how important these creatures are for understanding our world’s evolutionary history!

After all, the Megalosaurus was among the first three discovered dinosaur genera that served as the basis for the creation of the Dinosauria group!

Megalosaurus, a medium-large Jurassic predator of England, stalks the forest | Arthur Dorety via GettyImages
Megalosaurus, a medium-large Jurassic predator of England, stalks the forest | Arthur Dorety via GettyImages

On the other hand, while the fascination regarding its discovery is completely justified, it probably caused other aspects of this creature’s appearance and lifestyle to be neglected.

The lack of a complete skeleton that would shed light on many details we’re interested in also caused a lack of information.

Hopefully, future paleontological expeditions will reveal more fossils that will satisfy our curiosity!

Despite the interest scientists have shown in the genus, the popular media wasn’t as concerned with the Megalosaurus.

It’s not a very common appearance in documentaries, TV shows, or cultural books.

It does appear in some, but only briefly and usually in a form that’s quite misleading.

Megalosaurus bucklandii
Megalosaurus bucklandii | Nobumichi Tamura via iStock

There’s one TV series worth mentioning, however: the Dinosaurs TV series, which aired in 1991 on ABC.

Its main character, Earl Sneed Sinclair, is a Megalosaurus, as is Baby Sinclair, Earl’s youngest child.

As you’ve probably guessed, this TV series tells the story of a family of anthropomorphic dinosaurs.

Considering its importance in the history of Dinosauria, we’ll be waiting for more movies, books, or TV series featuring a Megalosaurus as the main character!


Having roamed the Earth 166 million years ago, the Megalosaurus was among the largest Middle Jurassic theropods.

It measured roughly nine meters (39.5 feet) long, had an elongated head, a short neck, and extremely robust hindlimbs.

The tail was quite long, and the forelimbs were short.

If it had been a predator, which hasn’t been fully confirmed, the Megalosaurus would have probably been capable of killing any terrestrial animal it hunted.

Considering that it was among the first genera that prompted paleontologists to even consider the existence of such creatures as dinosaurs, it’s no wonder the Megalosaurus is now one of the most renowned theropods in the world of science!


Was Megalosaurus bigger than T. rex?

The Megalosaurus was probably smaller than the Tyrannosaurus rex, as the latter could grow up to 12.3–12.4 meters (40.4–40.7 feet) long, whereas the Megalosaurus was only nine meters (29.5 feet) long.

Is Megalosaurus the first dinosaur?

While the Megalosaurus is the first non-avian dinosaur genus officially described, the members of this genus are not the oldest known dinosaurs.


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