The Stegosaurus is a plant-eating dinosaur from the Jurassic period. It’s best known for the impressive bony plates on its back. We’ll tell you everything you need to know, with seven key features and a profile.
Stegosaurus is one of the most famous dinosaur genera out there. You’ll find it in movies like Jurassic Park, in documentaries, and in kids' shows.
Its size, the bony plates on its back, and the sharp spikes on its tail make it easy to recognize.
Cool Facts About Stegosaurus
Stegosaurus Skeleton
In this chapter, you’ll find important info on the discovery of the Stegosaurus and the meaning of its name. We’ll also mention some of the ancient reptile’s relatives that look very similar to it. After that, we have the most important features of the Stegosaurus for you.
Discovery and Locations
The discovery of the Stegosaurus began back in the 19th century. The paleontologist Othniel Charles Marsh described and named several Stegosaurus species. Some of them have since been declared invalid, as you’ll see in the chapter on the classification of the Stegosaurus genus and species.
To this day, fossils from about 80 individuals and at least three species of Stegosaurus have been found in the Morrison Formation (USA) alone. In 2006, there was also a European find in Portugal.
Stegosaurus stenops is the most well-researched species. There is one complete skeleton and over 50 partially preserved skeletons of adults and juveniles.
In antiquity and the Middle Ages, people couldn’t explain the huge dinosaur bone finds. They thought they were the bones of giants or dragons and thus invented some of the mythical creatures we still know from fairy tales and legends today.
Meaning of the Name
Stegosaurus means something like "roof lizard." Its name is made up of the ancient Greek word for roof ("stegos") and lizard ("sauros"). The name was chosen in 1877 by the dinosaur researcher Othniel Charles Marsh.
He mistakenly assumed that the dinosaur’s bony plates lay on its back like overlapping roof tiles. In reality, they stood upright on its back.
Even in the early 20th century, it was still believed that the tail spikes were distributed all over the prehistoric giant’s back. We now know that there were only two pairs on the tail of the Stegosaurus.
Relatives of the Stegosaurus
The Stegosaur Huayangosaurus
Stegosaurus has many relatives from the group of stegosaurs (Latin: "Stegosauria"). So far, 13 genera have been proposed. Others have not yet been clearly assigned. They had different plates and spikes on their backs and were of different sizes. They also lived at different times in some cases.
The Wuerhosaurus, for example, had rather flat bone plates on its back, lived in the Lower Cretaceous, and grew up to 8 meters long. Huayangosaurus lived in the Middle Jurassic, was 4.5 meters long, and had more narrowly tapering plates on its back, as well as a large spike on each shoulder blade.
Kentrosaurus lived in the Upper Jurassic and reached a length of about 5 meters. Its bone plates were plate-like in the head and front back area, and from the middle of the back to the tail, they were shaped like sharp spikes.
7 Features of the Stegosaurus
In this chapter, you’ll learn all about the most important features of the Stegosaurus. This includes the classification of its genus and species, its habitat and diet, when it lived, and how old it got.
We’ve also put together body characteristics like its posture, size, weight, and speed for you. Afterward, you’ll find all the important key data summarized in a profile.
Classification of the Genus and Species
Classification of the Stegosaurus
The dinosaur genus Stegosaurus belongs to the order of bird-hipped dinosaurs (Ornithischia). It is counted among both the so-called Thyreophora (shield bearers) and the Eurypoda (broad feet). The Ankylosaurus also belongs to these two groups.
Stegosaurs are characterized by the fact that they walk on four legs (quadrupedal) and are plant-eaters (herbivores). They also have a double row of bone plates or spikes on their backs and at the end of their tails. Stegosaurus is the most popular representative and namesake of the stegosaurs.
Three species of Stegosaurus itself have been recognized, found in the Morrison Formation in western North America. This rock formation is known as the best source for dinosaur fossils in the USA. The species are Stegosaurus armatus, Stegosaurus stenops, and Stegosaurus ungulatus.
S. stenops ("narrow-faced roof lizard") was about 7 meters long and over 3 meters high. S. armatus ("armored roof lizard") probably reached a length of 9 meters and a height of 4 meters. S. ungulatus ("hoofed roof lizard") was similarly large.
Despite over 30 partial finds, Stegosaurus armatus was declared invalid as a type species because there are not enough complete bone finds.
S. sulcatus, seeleyanus, and affinis are considered possible synonyms for S. armatus, although research is not certain here either.
S. duplex is considered a junior synonym of S. ungulatus. Additionally, there were four other species that have since been assigned to other species.
When Stegosaurus Lived
The dinosaurs lived on our planet during the so-called Mesozoic Era. This era can be divided into three periods: First came the Triassic, then the Jurassic, and then the Cretaceous.
The Stegosaurus lived towards the end of the Jurassic period, specifically during the Late Jurassic from 157.3 to 147.7 million years ago. The time frames during this period are called the Kimmeridgian (about 152 to 157 million years ago) and the Tithonian (about 145 to 152 million years ago).
Habitat
Most Stegosaurus fossils were found in the Morrison Formation (USA)
Researchers assume that stegosaurs lived in rather dry regions, as hardly any of their footprints have been found. The only ones that could possibly be from Stegosaurus are in North America, but they have not yet been definitively assigned.
The climate during the time of the dinosaurs was described as a warm climate. It was consistently warm and more humid than today. About 2.6 million years ago, the Ice Age began on our Earth, and the poles froze. So, our current climate and seasons are not directly comparable to those of prehistoric times.
As a massive herbivore that survived for 10.4 million years, Stegosaurus must have had enough low-lying plants available. Its habitat probably included ferns, mosses, palms, and some conifers.
The Earth changes the tilt of its axis and its orbit over time. This, among other things, influences the change of day and night on Earth.
Therefore, a day 160 million years ago during the Jurassic period had only 23 hours. But a year also had 385 days. So, the time it took for the Earth to orbit the sun didn’t change.
Body Structure and Posture of the Stegosaurus
Tail spikes of a Stegosaurus
Stegosaurus had a strongly arched back, a relatively small and elongated skull, and a horny beak. Its front legs were shorter than its hind legs.
It had five short toes on each of its front feet and three on its hind feet. The inner two toes of the front feet were blunt like a hoof. Its body structure caused it to hold its head quite close to the ground and its tail rather high in the air.
The main feature of the Stegosaurus is its total of 17 to 22 bone plates on its back, which run in two rows. It also has two pairs of pointed spikes on its tail.
Its tail was probably very flexible, and it used it for defense. The bone plates were used to regulate body temperature or for communication with its own kind.
Compared to its body weight of up to 4.5 tons, the massive herbivore had a very small brain of only 80 grams. This observation led to the assumption that dinosaurs were not particularly intelligent. However, this is now largely rejected by researchers.
For a time, there was the idea that Stegosaurus had a second brain, as a cavity was found in the area of the tail base. It was thought that it could control its tail with it. Later, this was also discovered in sauropods and modern birds. Today it is assumed that this is an energy store that supplies the nervous system.
Weight, Size, and Speed
Stegosaurus ungulatus could be about 9 meters long, 4 meters high, and weigh 4.5 tons. Its weight is therefore roughly equivalent to the average weight of a full-grown elephant.
Stegosaurus stenops, which is the best researched and recognized today, was about 7 meters long and just over 3 meters high. Its weight was therefore probably somewhat less than that of S. ungulatus.
In Wyoming, the fossils of a juvenile were also found. Its length is 4.6 meters, and it is estimated to weigh 2.3 tons. The maximum speed of a Stegosaurus was about 6 to 7 kilometers per hour due to its cumbersome body build. This makes it one of the slower dinosaurs.
Sauropods (long-necks) walked at a speed of 2 to 4 kilometers per hour. A Triceratops was estimated to reach 32 kilometers per hour at a gallop, and a Velociraptor probably even up to 60 kilometers per hour at a sprint.
Lifestyle and Diet
Lifestyle and diet of the herbivore
Stegosaurus was a slow herbivore and thus belonged to the prey of some theropods (mostly bipedal carnivores). However, with its sharp spikes on its tail, it could defend itself quite well.
This is now also proven by an Allosaurus find, whose pelvic area was pierced from below by a Stegosaurus. The puncture wound caused a severe infection and also damaged the bone.
A full-grown Allosaurus could be between 11 to 13 meters long, 3 to 5 meters high, and weigh about 1.5 tons. So, it was a formidable opponent. Not much is known about the social behavior of the Stegosaurus. It was probably a herd animal, and its diet looked something like this:
- Ferns and cycads
- Mosses
- Fruits
- Low-growing conifers
It plucked these with its horny beak and probably crushed them with its flat, serrated teeth. Expansive chewing movements were not possible with its jaw.
To digest, Stegosaurus probably swallowed stomach stones (gastroliths), which ground up the plants in its stomach. Many dinosaur species did this back then. This behavior can still be found today in birds, crocodiles, and seals.
Life Expectancy
The exact life expectancy of dinosaurs has not yet been calculated. However, scientists assume that 'smaller' specimens did not live older than 40 years.
Herbivores the size of a Stegosaurus or Triceratops are sometimes compared to rhinos, which could live up to 50 years. However, there is no proof for this estimate.
Larger sauropods (four-legged long-necks) are estimated to have an age of between 50 and 120 years. It is unlikely, however, that the dinosaurs reached their actual life expectancy, as they lived under harsh environmental conditions.
Profile: The Stegosaurus
Profile: The Stegosaurus
In the following profile, you’ll find all the important features of the Stegosaurus summarized once again. This includes, for example, physical characteristics by which you can recognize it. But we’ve also noted its weight, size, and speed for you.
Additionally, you’ll find the classification of the species as well as the time and places where the dinosaur lived. Afterward, you’ll learn about the portrayal of the Stegosaurus in the media and the reason for its extinction.
- Genus Name: Stegosaurus ("Roof Lizard")
- Known Species: S. stenops, S. ungulatus (now invalid: S. armatus, not yet officially recognized: S. sulcatus)
- Family: Stegosauridae
- Group: Stegosaurs (Stegosauria)
- Order: Bird-hipped dinosaurs (Ornithischia)
- Period: Jurassic (Late Jurassic, 157.3–147.7 million years ago)
- Habitat: North America (Morrison Formation), Europe (Portugal)
- Diet: Herbivore
- Physical Features: Quadruped, short front legs, small elongated head, horny beak, between 17 and 22 bone plates in two rows on the back, two pairs of tail spikes
- Length: 9 meters
- Height: 4 meters
- Weight: 4.5 tons
- Speed: max. 6–7 km/h
Stegosaurus in the Media
Along with the Triceratops and the Brachiosaurus, Stegosaurus is one of the most famous herbivorous dinosaurs of our time. The most famous carnivores are Tyrannosaurus Rex, Spinosaurus, and Velociraptor.
The Stegosaurus gained its fame through its unique appearance and its size. It is often depicted fighting bipedal carnivores. It also appears again and again in various feature films and documentaries.
One example is the film series "The Land Before Time" (starting in 1988). There, it appears as a "spike-tail" named Spike. It can also be found in Walt Disney’s "Fantasia" (1940), "King Kong" (1933), as well as in Jurassic Park: The Lost World (1997) and Jurassic World (2015).
Another example is the video game "ARK: Survival Evolved" (2017), in which you can tame a Stegosaurus to ride on it.
Extinction of the Dinosaur
Extinction of the Stegosaurus
Stegosaurus went extinct 147.7 million years ago in the Late Jurassic. It walked our Earth for about 10.4 million years. The Jurassic was characterized by sea-level fluctuations and difficult living conditions.
It is likely that the changes in the environment and the further evolution of dinosaur species led to the extinction of the powerful herbivore. The mass extinction of the dinosaurs 66 million years ago was probably caused by a meteorite impact, various volcanic eruptions, and climate changes.
Dinosaurs ruled the Earth for about 169 million years. The first humans only appeared in the Stone Age about 2.6 million years ago. The early human Neanderthal lived only about 400,000 years ago. Our direct ancestor, Homo sapiens (modern human), was first documented 300,000 years ago.
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