An Ultimate Guide to Apatosaurus: The Deceptive Lizard

Leave a comment / / Updated on: 23rd September 2023

Name Meaning“Deceptive lizard”Height4 to 5 meters (13.1 to 16.4 feet)
PronunciationA-pat-oh-sore-usLength21 to 23 meters (68.8 to 75.4 feet)
EraMesozoicLate JurassicWeight16.4 to 22.4 metric tons (18 to 24.6 short tons)
ClassificationDinosauria,‭ Saurischia & TheropodaLocationOklahoma, New Mexico, Utah, Wyoming, and Colorado; United States, North America

Apatosaurus Pictures

Apatosaurus dinosaur drinking or eating
Apatosaurus dinosaur drinking or eating | Elenarts108 via Getty Images

The Apatosaurus

Gage Beasley Prehistoric's Apatosaurus Concept
Gage Beasley Prehistoric’s Apatosaurus Concept

The Apatosaurus, commonly known as the “deceptive lizard,” is by far the most renowned and studied dinosaur species.

Having lived around 152-150 million years ago during the Late Jurassic, the Apatosaurus is now regarded as one of the largest terrestrial animals that lived on Earth!

This dinosaur species was a quadrupedal herbivorous sauropod that inhabited the Morrison Formation.

Numerous fossils belonging to the genus were discovered in multiple U.S. States.

The Apatosaurus had a long neck and a whip-like tail, and it probably moved around with its neck straight and its head slightly angled downward.

Its limbs were robust and slightly shorter than in other species.

Apatosaurus | Elenarts108 via Getty Images

Before discussing more details, it is worth mentioning that the Apatosaurus genus has two species: Apatosaurus ajax and Apatosaurus louisae.

This is important in outlining the genus’ evolution, history, and classification.

As such, if you want to discover more, keep reading, as you’re about to learn some jaw-dropping details about this prehistoric giant!

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

Apatosaurus | Warpaintcobra via Getty Images

The Apatosaurus was undoubtedly a very large dinosaur!

Can you imagine it could reach lengths of up to 21-23 meters (68.8-75.4 feet) and weigh 16.4-22.4 metric tons (18-24.6 short tons)?

However, these numbers are based only on the type specimen.

Other individuals might have been even longer and heavier.

For example, some specialists indicate that the specimen discovered in Oklahoma is thought to have weighed twice as much as the type specimen used to describe the species.

They estimate a mass of 46-80 metric tons (50.7-88.1 short tons).

Moreover, they think that that individual wasn’t fully grown, indicating that these giant creatures could grow even larger!

On the other hand, other paleontologists think these numbers are exaggerated and support the numbers we mentioned at the beginning.

Either way, specialists believe that the Apatosaurus is almost equal to the giant Supersaurus, which is considered one of the world’s largest dinosaurs!

It measured approximately 33-35 meters (108-115 feet) long and weighed 35-40 metric tons (38.5-44 short tons).

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

The Brachiosaurus is another equal to the Apatosaurus, measuring 20-22 meters (65.6-72 feet) long!

The Apatosaurus wasn’t very tall – that is, if we compare it to other large dinosaurs.

They were still giants to the human eye, though! These impressive creatures were probably 4-5 meters (13.1-16.4 feet) tall at the hips.

The Brachiosaurus, for example, was twice as tall, reaching a height of 9.4-13 meters (30.8-42.6 feet)!

As for the overall appearance of the Apatosaurus, here’s what we could find out:

  • It was a quadrupedal dinosaur with a long, deep neck and a long, slender, and whip-like tail.
  • The tail consisted of up to 70-80 bones and might have reached lengths of more than 10 meters (32.8 feet).
  • The skull was relatively short, and the snout was squared.
  • The dinosaur had chisel-like teeth adapted for plant-eating. 
  • The neck featured multiple weight-saving air sacs.
  • The dinosaur had tall neural spines. 
  • The chest was unusually deep.
  • The forelimbs were shorter than the hind limbs, but both were very robust; in fact, they were stockier than they were long.
  • Each forelimb had a single claw, while the hind limbs had three claws on each.

Habitat and Distribution

All Apatosaurus fossils were discovered in the Morrison Formation. Specimens were found in Oklahoma, New Mexico, Utah, Wyoming, and Colorado.

Specialists think that the Morrison Formation was a semiarid ecosystem.

It features seasonal changes between wet and dry seasons, and it’s often compared to Portugal’s Lourinha Formation, although the latter was much wetter.

Scientists think the dinosaurs lived near the Morrison Basin, stretching from New Mexico to Alberta and Saskatchewan in Canada.

These ecosystems likely consisted of streams, rivers, lakes, floodplains, and swampy lowlands.

The Morrison Formation consists of siltstone, limestone, sandstone, and mudstone. 

Ancient soils
Brushy Basin Member showing the purple and red colors of paleosols (ancient soils) | Carpenter, Kenneth via Wikipedia (CC BY-SA 4.0)

Fossils belonging to Apatosaurus ajax and Apatosaurus louisae were recovered only from the upper Brushy Basin Member, a conglomerate found in Arizona, Colorado, New Mexico, and Utah and which was likely deposited in fluvial-lacustrine environments.

Conifers likely dominated the habitat, and other plant matter included cycads, ginkgos, horsetail rushes, and tree ferns.

Behavior and Diet

Does this make them semi-aquatic?
Does this make them semi-aquatic? | ratpack223 via Getty Images

While it was previously thought that the Apatosaurus and other large sauropods were semi-aquatic because they couldn’t support their weight on land, this theory is now rejected.

As such, the Apatosaurus was probably fully terrestrial, although it might’ve lived close to water sources.

These dinosaurs are thought to have walked around 25-40 kilometers (15.5-24.8 miles) daily.

They weren’t fast-moving, as they could only reach 20-30 kilometers (12.4-18.6 miles) per hour.

Compared to the speed of other dinosaurs, this isn’t a good performance.

Studies focused on sauropods showed that members of this clade, like the Bellusaurus, Alamosaurus, and some diplodocids, might’ve moved in herds.

On the other hand, some specialists suggest that the Apatosaurus was a solitary creature.

During their daily walks, Apatosaurus sauropods likely drank approximately 262 liters (69.2 gallons) of water daily.

An Apatosaurus drinking from a lake
An Apatosaurus drinking from a lake | JoeLena via Getty Images

Scientists calculated this upon researching its respiratory system and resting metabolism, concluding that the latter might have been reptilian, while the former, avian.

Only 262 liters a day – a piece of cake!

While some sources say that the tails were likely used in combat, other studies show they were too light and narrow to hit anything.

If the Apatosaurus ever used its tail to injure another animal, it would probably injure its tail even worse by causing muscle and skeletal damage.

It has also been argued that the tail was used for counterbalance, as a sound generator, or for sexual display.

Matthew G. Baron suggests another theory – that diplodocid sauropods used their tails to communicate with other individuals.

Supposedly, the tail offered animal-to-animal contact during the migration or herd movements.

However, if the theory that the Apatosaurus was more solitary than other dinosaurs in its ecosystem is true, this tail function might not apply to this genus.

Now you’re probably wondering what these giant creatures ate to grow this big, right?

Well, the Apatosaurus was a plant eater – nothing easier than that!

Apatosaurus dinosaur drinking or eating
Apatosaurus dinosaur drinking or eating | Elenarts108 via Getty Images

Since it had a square snout, it was probably a ground-height nonselective browser.

This means that these dinosaurs fed at around 1 meter above the ground.

This likely ruins the common belief that long-necked sauropods usually stand with their necks high up in the air, feeding on the tallest vegetation in the area.

In reality, they couldn’t even stretch their necks too far upward and usually kept them low to the ground, while the tail was probably kept higher than the neck.

However, other theories suggest that the Apatosaurus and other sauropods kept their necks angled upward or straight and only the head pointed downward.

Either way, scientists think the Apatosaurus likely ate horsetails, algae, seed ferns, and cycloids.

Life Cycle

Tracks of a juvenile
Tracks of a juvenile | James St. John via Flickr (CC BY 2.0)

All dinosaurs reproduced by laying eggs, and the Apatosaurus was no exception.

Baby dinosaurs were likely born precocial, as were many baby dinosaurs.

This means that they were born somewhat independent.

Moreover, other sauropod studies suggest that some age-mixed herds probably showed parental care until the young reached adulthood.

Still, since most studies focus on sauropods overall, whether the Apatosaurus specifically exhibited this behavior toward its young is unknown.

Another research paper shows that they grew rapidly compared to other species, requiring only about 10-15 years to mature fully.

Some studies show that these creatures add approximately 5,000 kilograms (11,000 lb) annually.

This sounds extraordinary!

Juvenile A. sp. mount
Juvenile A. sp. mount, Sam Noble Oklahoma Museum of Natural History | Matt Wedel via SV-POW

Well, that’s what other scientists thought, so they conducted another research paper that resulted in completely different numbers.

Thomas M. Lehman and Holly N. Woodward presented an alternative model growth curve, arguing that the Apatosaurus reached its adult mass when it was 70 years old!

They showed that the maximum annual weight added was 520 kilograms (1,146 lb).

Nevertheless, not all scientists support this theory.

Evolution and History

Apatosaurus | MR1805 via Getty Images

The Apatosaurus is part of the Diplodocoidea superfamily under the Sauropoda clade.

A study suggests that the earliest diplodocid was found in East Asia, thus indicating that these creatures probably appeared around 15 million years earlier than previously thought.

This superfamily is then divided into two subgroups, Haplocanthosaurus and Diplodocimorpha.

The latter hosts the Diplodocidae family, which the Apatosaurus is a part of.

The members of this family are thought to have evolved in what is now known as North America because most fossils belonging to them were found on that continent.

The closest relatives to diplodocids are dicraeosaurids (Dicraeosauridae), and they are thought to have separated during the Middle Jurassic. 

As mentioned, the Apatosaurus is now classified into the Diplodocidae family and the Apatosaurinae subfamily.

It’s a close relative to the Barosaurus, Supersaurus, and Diplodocus.

The first fossils belonging to Apatosaurus were found in 1877 and included a partial postcranial skeleton and a partial braincase.

A. ajax skull
A. ajax skull, specimen CMC VP 7180 from 1877 | James St. John via Flickr (CC BY 2.0)

Based on these fossils, Othniel Charles Marsh named the Apatosaurus ajax species.

In 1879, a more complete specimen was discovered in Wyoming, but it was attributed to Brontosaurus excelsus.

In 1903, a study describing a well-preserved skeleton discovered in Colorado showed that these fossils were similar to those previously attributed to Brontosaurus.

Elmer Riggs, the author of the study, concluded that the remains were wrongly attributed to Brontosaurus.

In fact, they belonged to an adult Apatosaurus and the confusion was caused by the fact that the previously described Apatosaurus ajax was likely a young dinosaur.

As such, the scientist concluded that the terms Apatosaurus and Brontosaurus should be synonyms and named the skeleton wrongly attributed to Brontosaurus Apatosaurus excelsus.

So if you ever wondered why people confuse the Brontosaurus with the Apatosaurus, here’s the answer!

Still, even this theory was subsequently disregarded, as other paleontologists argued that the specimen was much too different from other Apatosaurus specimens.

The Brontosaurus is now regarded as a separate genus, and the Apatosaurus excelsus became Brontosaurus excelsus, as did two other species wrongly attributed to Apatosaurus; Apatosaurus parvus and Apatosaurus yahnahpin.

Apatosaurus dinosaur walking in the desert by day
Apatosaurus dinosaur walking in the desert by day | Elenarts108 via Getty Images

As you can see, establishing the evolution and history of the Apatosaurus was not an easy paleontological task!

Many classifications and results turned out to be wrong, and the discovered specimens were reclassified multiple times, not to mention how many studies focused on establishing whether their classification could be supported further.

Understanding these aspects is essential in outlining the species’ evolution and relationship with other species. 

This being said, we must mention that the Apatosaurus ajax didn’t remain the type species.

A skeleton found in Utah soon became the holotype and was named Apatosaurus louisae.

It is now the type species of the genus. 

Interactions with Other Species

Apatosaurus and a Theropod | Elenarts108 via Getty Images

The Morrison Formation is probably one of the world’s richest formations in terms of fossils, as hundreds of them were discovered there!

This indicates that the region supported many prehistoric creatures, especially dinosaurs!

Here’s a list of dinosaurs that are thought to have inhabited the Morrison Formation during the same period as the Apatosaurus:

  • Sauropods like Smitanosaurus, Suuwassea, Galeamopus, Camarasaurus, Brachiosaurus, Brontosaurus, Barosaurus, and Supersaurus
  • Theropods like Allosaurus, Fosterovenator, Ceratosaurus, Torvosaurus, Saurophaganax, and Ornitholestes
  • Ornithischians like Nanosaurus, Dryosaurus, Laosaurus, Uteodon, Camptosaurus, Stegosaurus, Hesperosaurus, Mymoorapelta, and Gargoyleosaurus.

Besides this, the formation was home to numerous lizard, salamander, frog, turtle, crocodile, and fish species. Various mammaliforms also inhabited the area.

As you’ve probably already noticed, most dinosaurs were herbivorous.

So, you’re probably wondering how the ecosystem could support these giant creatures, right?

Apatosaurus dinosaur walking in the desert
Apatosaurus dinosaur walking in the desert with calamite and onychiopsis plants by day | Elenarts108 via Getty Images

Above all, how could they have coexisted in the same habitat if they had the same diet?

Since the dinosaurs varied in body shape and adaptations, each species likely had a specialized diet and unique feeding strategy, allowing them to feed on different plants at different times and heights.

However, we cannot rule out intraspecific and interspecific combat.

Carnivorous dinosaurs like the theropods mentioned above were also inhabitants of the Morrison Formation.

Although smaller than the Apatosaurus, these carnivores are known to have hunted large dinosaurs, so we cannot deny the possibility that the Apatosaurus served as prey for them.

Cultural Significance

Apatosaurus at a snow-covered lumber yard
Apatosaurus at a snow-covered lumber yard in Jurassic World: Dominion | PopCultMedia via Jurassic Park Fandom

As you’ve probably already noticed, the Apatosaurus was and still is the subject of hundreds of research papers and studies.

Being one of the largest terrestrial animals that ever roamed the Earth, it’s unsurprising that the genus is of great interest to paleontologists and other specialists working in related fields.

This puts it easily among the most studied and renowned dinosaur species!

The genus is also mentioned in numerous books about dinosaurs, both scientific and children’s books.

Besides this, it’s one of the most famous creatures in the Jurassic universe, having appeared in about four movies and six video games! 


The Apatosaurus is a famous dinosaur, to say the least, being known as one of the largest terrestrial animals that ever roamed our Earth.

It was discovered with the help of fossils found in the Morrison Formation, a cradle for prehistoric creatures such as Sauropods, Theropods, and Ornithischians.

Despite being first discovered in 1877, the Apatosaurus is still being intensively studied today.

On top of that, a great part of its popularity stems from its media portrayals.

After all, it’s only fitting for one of the largest dinosaurs ever!

Paleontologists and scientists across the world are constantly looking into this giant.

It cannot escape the laws of paleontology, so to speak, as even its type species was replaced from A. ajax to A. louisae.

Even though we know so much about this giant, at the end of the day, we might realize we know just a little!


Did Apatosaurus and T-Rex live at the same time?

The Apatosaurus and the T-Rex lived during different periods.

The former inhabited Earth around 152-150 million years ago, while the T-Rex lived 68-66 million years ago.

What does Apatosaurus‘ scientific name mean?

Apatosaurus comes from two Greek words: apatē for deceptive and sauros for lizard.

As such, this dinosaur is often called the deceptive lizard.


About The Author

Leave a Reply

Discover more from Gage Beasley Prehistoric | Recapping Timeless Creatures

Subscribe now to keep reading and get access to the full archive.

Continue reading

Scroll to Top