Stegosaurus Guide | Ancient Beasts

"How much would you like to learn about the infamous herbivore dinosaur, Stegosaurus? Read more about all the details right here!"

Stegosaurus was a herbivorous ornithischian dinosaur that lived during the Late Jurassic Period. Its name stands for ‘roof lizard’ based on the armor plates along its back and tail. Fossils for more than 80 of these magnificent beasts have been found; that’s why we know so much about them today.

In this genus guide, we’ll look at the extensive history of discoveries over the centuries. You’ll see the chief characteristics of the magnificent dinosaurs, their popularity in entertainment media, and some of the top questions.

Welcome to Late Jurassic Park, and enjoy the show!

Welcome to Late Jurassic Park, and enjoy the show!

Overview of the Stegosaurus genus

It’s hard to miss the sight of this terrific prehistoric creature. The Stegosaurus was truly one of a kind with its kite-shaped plates and spiked tail. Many dinosaur lovers enjoy seeing this genus at museums and shows for any tales of these ancient beasts.


These ornithischian herbivores were massive and bulky, walking on all fours as they hunted for food among the vegetation. With its armor, it was well-defended against massive predators, even the fearsome Allosaurus. So far, three species have been identified, but there’s hope that more will be found.


Since it only lived until the Early Cretaceous Period, chances are low that it would have met the ferocious Tyrannosaurus Rex from the Late Cretaceous. Instead, it would have had company among Brachiosaurus, Diplodocus, Apatosaurus, and Ceratosaurus.

Learn why dinosaurs went extinct while other animals survived!
Learn why dinosaurs went extinct while other animals survived!
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The extinction theory of dinosaurs has been a controversial topic since the time it was first introduced. Read more on this sensitive topic.

Stegosaurus classification

Kingdom: Animalia

Phylum: Chordata

Clade: Dinosauria

Order: Ornithischia

Clade: Thyreophora

Suborder: Stegosauria

Family: Stegosauridae

Subfamily: Stegosaurinae

Genus: Stegosaurus

Stegosaurus Fact Card

Stegosaurus Fact card


When was Stegosaurus discovered?

There were many discoveries of Stegosaurus over the centuries, with two dinosaur rushes playing pivotal roles. It’s best to break up the history into different parts, so it’s easier to digest the information mentally. The first Stego fossil was discovered in 1877, as you’ll see below.

Here’s a concise history of Stegosaurus discoveries.

Initial Bone Wars

The Bone Wars was a period in American history where paleontologists rushed to find as many fossils as possible in an effort to beat each other. The two main competitors were Othniel Charles Marsh and Edward Drinker Cope, who had different teams across dig sites. It mainly took place during the late 19th century. 

In the Marsh camp

It was Arthur Lakes who discovered the first Stegosaurus remains during the Bone Wars. His team discovered a dermal plate, caudal vertebrae, and other postcranial elements. The location was known as Lakes’ YPM Quarry 5, situated in Morrison, Colorado.

This holotype was labeled YPM 1850, named Stegosaurus armatus when Marsh studied the fossils in 1877. At first, he thought it was a marine animal, like a massive turtle. Later, he named it the roofed lizard as Marsh believed the plates relaxed flat on the back of the extinct dinosaur. Unfortunately, later discoveries unearthed that some of the bones belonged to other species.

Thanks to this confusion, the International Code of Zoological Nomenclature repositioned some of the remains under Stegosaurus stenops. It was also identified that other remains from this collection actually belonged to Diplodocus and Allosaurus. 

It was clear that Stegosaurus was off to a rough start.

Back over at the Cope camp

Cope had found some remains in Cope’s Quarry 3 in Garden Park, Colorado, in a place named Cope’s Nipple. While he named the dinosaur Hypsirhophus discurus, he referred to it as a Stegosaurian. This was in 1878. 

At about the same time, one of Cope’s collectors discovered more Stego remains at Como Bluff, which became the infamous skeleton mount at the American Museum of Natural History. The specimen was labeled AMNH 5752.

Lakes return

With the Bone Wars continuing, Arthur Lakes made plenty more Stegosaurus discoveries at Quarry 13 in 1879. He and William Reed specifically collected fossils of Stegosaurus ungulatus during this time, labeled YPM 1853. There were several plates, vertebrae parts, partial limbs, and more. It also had the roof-like plates that the genus was known for.

In 1887, Marsh named more bones which led to the discovery of two more species. He named them Stegosaurus duplex (YPM 1858) and Stegosaurus sulcatus (USNM V 4937). He thought he had discovered another species he called Stegosaurus affinis, but those specific remains have since vanished. Therefore, it was struck from official records.

The top Stegosaurus discovery

One of the most remarkable discoveries of Stegosaurus remains happened in 1885. The fossils were from a young adult where an almost complete skeleton was unearthed. Marshall P. Felch is credited for collecting the fossils for over a year, which were located in Colorado in Morrison Formation strata from his own quarry. 

Once the bones were labeled, Felch shipped them to Marsh in 1887, who promptly named the species Stegosaurus stenops due to the narrow face. Marsh then used the remains of Stegosaurus ungulatusI, filled in the missing pieces with fossils from S. stenops, and present the first complete reconstruction of the genus.

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First Skeleton Mounts

With several Stegosaur specimens now available, the different teams went about preparing them for mounting at prominent museums and locations. Here’s a quick history of the different mounts and further discoveries during this time.

Mounting of Stenops and UngulatusI

The S. ungulatus (YPM 1853) remains were the first to be mounted. It belonged to the Arthur Lakes discovery, followed by more bones found by Marsh as mentioned earlier. This Stegosaur mount ended up in the Peabody Museum of Natural History, established by Richard Swann Lull in 1910.

Regarding the Stegosaurus stenops skeleton that Marsh reconstructed with S. ungulatus parts (USNM 6531), it ended up in the National Museum of Natural History located in Washington DC. The display appeared in 1915, where you can still see it to this day.

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Arguments about plate arrangement

As you already know, the original thought about the plate’s on the Stegosaurus back was that they were flat like roof shingles, hence the genus name. However, with the mounting of these skeletons, it was decided that the plates ran in two rows along the back next to each other above the ribs.

In 1901, Frederick Lucas named a new species: Stegosaurus marshi. While he would later reclassify it to the Hoplitosaurus genus, it set him on the path of trying to decipher Stego’s appearance. His initial thought was along the line of the two parallel rows of plates along the back. However, his ideas would change soon after.

Lucas asked Charles R. Knight to prepare an artistic reconstruction, or lifelike restoration, of S. ungulatus. He came to the belief that the plates did indeed run in two rows, but alternating instead of alongside each other. When writing about this matter in 1910, Richard Swann Lull believed that the alternating pattern described was probably due to the bones shifting in the ground during fossilization.

Lull’s mount at the Peabody Museum of Natural History presented the plates in paired rows to represent his theory. Charles Gilmore disagreed with Lull, discussing in 1914 how other remains also showed alternating plates that had nothing to do with shifting fossils. Once Lucas’ and Gilmore’s interpretation of alternating plates was accepted, the Peabody skeleton was reconstructed in 1924.

To this day, scientists and paleontologists still debate the plate arrangement of Stegosaurus. Here are four plate arrangements that have been considered since the first discovery:

  • Lying flat on the back like roof shingles
  • Single row of plates
  • Paired double row
  • Alternating double row (the prominently accepted arrangement)

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The Next Dino Rush

While the first Bone Wars was largely over for Marsh and Cope, the mounting of dinosaurs awoke the second dinosaur fossil rush among prominent museums. The three major institutions that rallied to find more remains were the Carnegie Museum of Natural History, the American Museum of Natural History, and the Field Museum of Natural History.

The AMNH sent its first expedition to the west in 1897. The teams discovered several Stegosaurus fossils at Como Bluff at a location called Bone Cabin Quarry. In a rush to beat the competition, they mounted the incomplete skeleton in 1932 without sufficient descriptions. While the Field Museum of Natural History didn’t make any discoveries at this time, it does have these AMNH mounts on display.

The Carnegie Museum had a bit more luck. They went to Carbon County in Wyoming, searching in a place called Freezout Hills. Spending more than two decades uncovering remains until about 1920, they discovered several bones that helped them reconstruct one of the most complete Stegosaurus skeletons. Labeled CM 11341, This S. ungulatus structure was mounted in 1940.

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Revival of Discoveries

There’s a scientific period of time called The Dinosaur Renaissance. In summary, it consisted of a renewed interest in finding more remains that began in the late 1960s. Many important discoveries were made, including the suggestion that these ancient beasts were warm-blooded and not cold-blooded. 

The Kessler Site

Before the Dinosaur Renaissance kicked off, there was a significant discovery made in 1937 that would eventually spark renewed interest in the late 1960s. Let’s call this the prologue. Frank Kessler, a high school teacher, went on a nature hike in Garden Park, Colorado. Once he realized what he had found on his walk, he called the Denver Museum of Nature and Science.

With the news of a possible dinosaur discovery, the DMNS sent Robert Landberg to check it out. The paleontologist went to the specified area with his digging crew, where they were able to excavate 70% of a complete Stegosaurus skeleton. They also found remains of crocodiles and turtles, as a matter of interest.

The location was named The Kessler Site in honor of Frank. The DMNS mounted the skeleton in its museum in 1938 with the help of steelworker Phillip Reinheimer. It would remain there until 1989, which is when the DMNS curator decided to make some changes to the fossil section.

The Small Quarry

No, the name doesn’t reflect the size of the quarry. Instead, it’s named after Bryan Small. The DMNS sent a new team in 1989 to see if it could discover more Stegosaurus bones. Small was looking near the Kessler Site when he founds more remains. Hence, the location would be named after him.

The most important aspect of this discovery is that it clarified how the plates were positioned and the placement of spikes on the end of the tail. The plates were alternatively placed in two rows, confirming the most prominent idea of how the armored plates ran along the back.

Bollan Stegosaurus

Harold Bollan helped with the discovery of a Stegosaurus skeleton that was 40% complete in 1987. The site is near the Dinosaur Journey Museum, also located in Colorado. While it was named after Bollan, it wasn’t the only remains found during this time. Suddenly, discoveries were being made in other parts of the world.

In 2007, more Stegosaurus remains were found in the Upper Jurassic Lourinha Formation (Portugal). It was listed as Stegosaurus ungulatus and is still on display today. Remains found at Jensen-Jensen quarry were presented and described in 2014, which is located in Utah. Many more fossils would appear in other locations during this time.

Sophie the Stegosaurus

One of the most complete Stegosaurus skeletons is Sophie, which contains 85% of the entire structure. Bob Simon found the first remains in 2003, located at Shell, Wyoming, in a site called Red Canyon Quarry. While the site was on private land, the US federal authorities took over the region. Later, they would hand the remains to the Natural History Museum in London. It was mounted in 2014 and partially described in 2015.

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Which characteristics define Stegosaurus?

You’ve been on an exciting journey with us so far. Now that you know when all the discoveries were made, it’s time to show you what the studies have revealed. Here are the top characteristics of the Stegosaurus species.

The skull

One of the most striking features of Stegosaurus is how small the head was in comparison to the rest of the body. The hole that was present between the eyes and nose (antorbital fenestra) was also tiny. Due to the low position of the head, many paleontologists believe that it fed on low vegetation.

It’s possible the dinosaur had a small beaky mouth instead of front teeth for breaking food off the plants. Also, the layout of the jaw may have prevented any view of the side and back teeth from view. There’s a good chance that the skull and outline of the jaw and teeth were unique to most of the Stegosaurians.

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Skeletal structure

The main bone structure of Stegosaurus is divided into two: cervical (the neck) and dorsal (the back). Along this spine, there were 10 cervical and 17 dorsal vertebrae in general, based on the findings of Stegosaurus stenops. Some species have more, while others have less.

When you move past the first few dorsal vertebrae, the centrum is more elongated. In other words, they stretch out more. There are four sacral vertebrae, but one of the dorsals is somehow part of this structure. One unique feature is a small bump located along the back, which performs the function of forming the base of the tricep group of muscles.


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Brain size

There have been many discussions and presentations about the estimated size of Stegosaurus’ brain. Some say it was as small as a walnut, while others scoff at this idea. These others say it was probably as big as a dog’s brain.

However, the main idea that’s in common among all trains of thought is that the brain was incredibly small compared to the rest of the body. The small skull didn’t leave much room for a large brain. It’s also believed that Stegosaurus had the smallest brain among dinosaurs. 

Tail Spikes

In 1982, cartoonist Gary Larson referred to the tail spikes of Stegosaurs as Thagomizers. While it’s not an official scientific name, it soon became the unofficial canonical name for a tail end with four spikes arranged on it. 

While some early suggestions mention the spikes being purely decorative, some later evidence provided otherwise. An Allosaurus skeleton has puncture wounds from a Stegosaurus Thagomizer, revealing that they may have been defensive weapons. With one swat of the tail, these giant herbivores had a powerful way to protect themselves and their families.


One of the clearest ways to identify a Stegosaurus is by the plates. These kite-armor objects are what sets Stegosaurids apart from other dinosaurs, as it seems to be the only group with these formations. On any given species, you have between 17 and 22 of these plates. 

Interestingly enough, these bony scales weren’t attached to the bones. Instead, they rose from the skin of the Stegosaurus, similar to crocodiles. Another interesting assumption is that the arrangement of plates differed between species. However, there are still discussions around if they were paired or alternatively arranged.

Paleoecology: Which dinosaurs lived with Stegosaurs?

Of course, Stegosaurs weren’t the only dinosaurs around during the Late Jurassic into the Early Cretaceous Period. There were many others you’ll recognize, showing you the ecology of the times. It’s always fascinating to compare other families and genera during the same periods and in the same locations.

This list represents some of the dinosaurs that lived with Stegosaurus:

  • Allosaurus
  • Saurophaganax
  • Torvosaurus
  • Ceratosaurus
  • Marshosaurus
  • Stokesosaurus
  • Ornitholestes
  • Coelurus
  • Tanycolagreus
  • Brachiosaurus
  • Apatosaurus
  • Diplodocus
  • Camarasaurus
  • Barosaurus
  • Camptosaurus
  • Gargoyleosaurus
  • Dryosaurus
  • Othnielosaurus
  • Drinker

Games and Movies that feature Stegosaurus

Tyrannosaurus Rex wasn’t the only popular dinosaur in movies and games. Due to its unique design, plates, and shape, Stegosaurus was another dino that ended up in several entertainment media. 

Since the list is way too long, we’ve shortened it to a few of the best. Here are movies and games with Stegosaurus in it:

  • Almost every Jurassic Park or World game or movie
  • ARK: Survival Evolved
  • Stegosaurus Simulator
  • Talking Stegosaurus
  • Stegosaurus: Robot Dinosaur
  • Cell to Singularity
  • The Land before Time
  • When Dinosaurs Roamed
  • Fantasia
  • Walking with Dinosaurs

Seven major dinosaur groups

Did you know that the Stegosaurs have an official group on its own? Paleontologists have named seven major groups that all dinosaurs form part of in one way or another. Of those, Stegosaurus is one of the five ornithischian herbivores on the list, standing out from the others.

The seven major dinosaur groups:


Final Thoughts on the Stegosaurus

Very few people that know about dinosaurs are unfamiliar with Stegosaurus. Since the first discovery, scientists have been trying to study as much about this genus as possible. Fans around the world love the Stego, with it featured in many games, movies, and other merchandise. We’re proud to include it in our World of Dinosaurs library.


Top questions about Stegosaurus

You’re almost at the end of your journey here with us regarding the Stegosaurus genus. We just want to touch on the top 10 questions people always ask about this dinosaur. If you have any other queries, please let us know.

No. Tyrannosaurus lived in the Late Cretaceous period while Stegosaurus existed in the Late Jurassic into the Early Cretaceous. There’s little evidence that Stego ever met T-Rex, especially with so much time between them.

Since these two dinosaurs are so popular, it’s with little surprise that many movies, games, and other media often portray them together. They sometimes engage in battles to answer the question of who would win in a fight. In reality, there was more chance of an Allosaurus meeting the Stegosaurus instead of T-Rex.

One of the most unique features of the Stegosaurus was the kite-plate arrangement on its back, ending in a spiked tail. No other dinosaur group is known to have these formations, which is why they are portrayed in so many artistic impressions. There are still many discussions about these plate formations, too.

Of course, there are a few other aspects that stand out with this dinosaur. It had a small head compared to the rest of its body. Also, the brain was tiny, while the long body had several vertebrae that supported the skeleton.

Plenty of Stegosaurus remains have been found during the first and second Bone Wars. Also, there have been revivals recently to try and find more skeletons to get a better understanding of these magnificent creatures. To this day, paleontologists and fans alike are still obsessed with how it looked and lived.

There have been a few misunderstandings from the Stegosaur bones found, such as the plate arrangement and whether there was a second brain in the tail. This is why discovering more fossils for this genus is so important to understanding it better.

As the transition from the Late Jurassic into the Early Cretaceous occurred, the environment and climate changed a lot. It became hotter and more humid, which resulted in more specialized theropods forming. Therefore, the extinction of Stegosaurus is usually seen as a combination of climate change, advanced predators, and the decline of vegetation that the dinosaur enjoyed.

As the Early Cretaceous evolved, the temperatures went higher or lower than usual, depending on if they lived in the northern or southern hemisphere. Fauna responded to these changes by either dying out or adapting. Due to this decline in food and the rise of stronger carnivores, the Stegosaurus didn’t last to see the Middle or Late Cretaceous.

Stegosaurids lived in packs or herds, usually in small to large groups. They were protective of each other, but that didn’t mean they were violent. On the contrary, paleontologists regard them as peaceful herbivores, only becoming aggressive if there was any form of danger in the area.

If you can, imagine a herd of elephants traveling together and protecting the young as they search for food and water sources. Stegosaurus was pretty much the same, and would easily have watched humans without any hint or sign of aggression unless they had cause to believe there was a risk to its life.

Any of the large carnivores of the time would probably have won a fight against Stegosaurus, if they could get passed the herds and tail spikes. The plates would have also caused a hindrance, which means the theropods would have aimed for the belly or sides. If T-Rex was alive at the time, it would have easily defeated a Stego in battle.

Of course, it’s all theoretical. If enough Allosaurs surrounded a lone Stegosaurus, they would have had a fair chance of defeating the dinosaur. Since Stegosaurids traveled in groups, it would have been challenging to find one on its own.

Since there are so many interesting elements to the Stegosaurus, it’s challenging to pin down only three. The ones that kids love the most include the dinosaur weighing as much as the average car, that the name means roof-lizard, and that it has a small brain compared to the rest of its body.

There are other exciting facts about Stegosaurus. The plate arrangements and spiked tail are only two of them. When traveling in herds, these dinosaurs acted similar to the modern-day elephant. However, the plates protruding from the skin were more akin to modern crocodiles.

One of the oldest Stegosaurids ever found was discovered in Morocco in 2019. Also, Paranthodon is a genus of Stegosaurians that is believed to exist in the locations called South Africa today. It was one of the first Stegosaurs from Africa to be found. 

Plenty of other Stego fossils have been found in Africa since then, together with Triassic and Jurassic dinosaurs. Other dinos found on the continent include Coelophysis, Melanorosaurus, Dracovenator, Massospondylus, Heterodontosaurus, Euskelosaurus, Lesothosaurus, and Abrictosaurus.

Two of the top Stegosaurus predators during its time were the Allosaurus and Ceratosaurus. Theropod predators were becoming more evolved as the Early Cretaceous appeared, making Stegos more vulnerable to attacks. These two carnivores were on the top of the list for ones that ate Stegosaurids.

That didn’t mean it was helpless. As mentioned, the spikes and plates helped defend these marvelous creatures, the former being used the most to puncture the carnivores. If they remained in herds, they had a better chance of survival. However, as the food dwindled and they became weaker, the Stegosaurs became more susceptible to attacks.

Crocodiles are the closest living animals to Stegosaurus, and almost all dinosaurs. They’re related to some of the original Archosaurs. Still, the plates on the back of the herbivores are akin to the scales on crocodiles and alligators, which makes them even more closely related.

That’s only if you look at the biological aspects. When studying their behavior and size, they’re also much like the elephants of today. They traveled in herds in much the same way, feasting on low to medium vegetation. Also, they protected their young and families with the spikes on their bodies, even though they were located on different parts of the body.

Picture of Shaun M Jooste

Shaun M Jooste


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