What is a Stegosaurus?

Stegosaurus is a genus of plated dinosaurs (Stegosauria) from the Late Jurassic Period, roughly 159 million to 144 million years ago. Recognizable for their spiked tails and a series of large, triangular bony plates along their backs, they could grow up to 9 meters (30 feet) long. Paleontologists once thought the plates were for protection, but now believe they alternated along the backbone and may have been used for thermoregulation, either releasing body heat or collecting it like solar panels. Two pairs of bony spikes on the tail's end were likely used for defense or display. Stegosaurus is closely related to ankylosaurs, sharing dermal armor and a simple curved row of small teeth. Stegosaurus lost the flank armor of its early relatives.

What did a Stegosaurus look like?

The Stegosaurus was a plated dinosaur from the Late Jurassic Period, around 159 million to 144 million years ago. It is recognizable for its spiked tail and large, triangular, bony plates along its back. Stegosaurus grew to about 6.5 meters (21 feet), but some reached 9 meters (30 feet). Its forelimbs were much shorter than its hind limbs, giving its back an arched appearance. The feet were short and broad. Two pairs of pointed bony spikes were present on the end of the tail, which were likely defensive weapons. The plates along the back may have been a temperature-regulating system.

When and where did Stegosaurus live?

Stegosaurus lived during the Late Jurassic Period, approximately 159 million to 144 million years ago. Their fossils have been discovered in various locations, including North America, Africa, Europe, and Asia. Notably, the Stegosaurus genus, which includes the species S. sulcatus , S. ungulatus , and S. stenops , was excavated from the Morrison Formation in Utah, U.S.

What did Stegosaurus eat and how did it get its food?

Stegosaurus was a herbivorous dinosaur that lived during the Late Jurassic Period. It ate plants, but its weak dentition indicates that it likely fed on plants that did not require much preparation by the teeth. Because of its low build, paleontologists believe Stegosaurus likely fed on low shrubbery. Stegosaurus had a small, long, low, and narrow skull, with little space for sizable jaw muscles. The weak dentition consisted of small, laterally compressed, leaf-shaped teeth arranged in short, straight rows. It is possible that bacteria in its digestive tract helped break down the cellulose-rich Jurassic plant tissues. Although none have been discovered in Stegosaurus specimens, gastroliths, or stomach stones, may have aided its digestion.

Why did Stegosaurus have plates and spikes on its body?

The Stegosaurus , a plated dinosaur from the Late Jurassic Period, is known for its distinctive plates and spiked tail. The arrangement and purpose of the plates have been subjects of various hypotheses. While it was initially believed that the plates served as protection for the backbone and spinal cord, new discoveries indicate that the plates alternated along the spine. The presence of numerous blood vessels in the plates supports the theory that they functioned for thermoregulation , either releasing body heat or collecting it from the sun. Two pairs of bony spikes on the tail are thought to have served as defensive weapons or possibly for display. The exact function of these features remains uncertain, but display and species recognition are likely possibilities.

How do scientists study and learn about Stegosaurus today?

Scientists study Stegosaurus by analyzing fossil remains found worldwide, including in North America, Africa, Europe, and Asia. These studies involve reexamining existing specimens and considering new discoveries to understand the dinosaur's characteristics. Paleontologists investigate the arrangement and purpose of the Stegosaurus's plates, initially believed to be protective. The discovery of blood vessels in the plates led to the hypothesis that they served for thermoregulation, either releasing heat or collecting it like solar panels. Researchers also study the Stegosaurus's tail spikes, presumed to be defensive weapons.

Stegosaurus

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Images

Lifelike outdoor statue of a Stegosaurus dinosaur with large, upright plates along its back, set among trees and greenery at Dinopark in Belgorod, Russia.

Illustration of a Stegosaurus, a large herbivorous dinosaur from the late Jurassic period, shown with two rows of tall bony plates along its back. Human figures and a dog are included for scale, highlighting the dinosaur's size, which could reach 30 feet (9 meters) in length.

Fossil skeleton of a Stegosaurus, named Apex, displayed upright in a gallery at Sotheby's New York, with a wall sign reading Apex the Stegosaurus behind it.

Illustration showing the body shapes of five extinct reptiles: the long-necked Elasmosaurus, the streamlined marine Kronosaurus, the small Placodus, the large long-tailed Apatosaurus, and the spiked Stegosaurus.

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Related Topics:: Late Jurassic Epoch

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Stegosaurus

dinosaur genus

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What is a Stegosaurus?
Stegosaurus is a genus of plated dinosaurs (Stegosauria) from the Late Jurassic Period, roughly 159 million to 144 million years ago. Recognizable for their spiked tails and a series of large, triangular bony plates along their backs, they could grow up to 9 meters (30 feet) long.

Paleontologists once thought the plates were for protection, but now believe they alternated along the backbone and may have been used for thermoregulation, either releasing body heat or collecting it like solar panels. Two pairs of bony spikes on the tail's end were likely used for defense or display.

Stegosaurus is closely related to ankylosaurs, sharing dermal armor and a simple curved row of small teeth. Stegosaurus lost the flank armor of its early relatives.
2 Britannica Sources
1. Stegosaurus
2. dinosaur: Stegosauria
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What did a Stegosaurus look like?
The Stegosaurus was a plated dinosaur from the Late Jurassic Period, around 159 million to 144 million years ago. It is recognizable for its spiked tail and large, triangular, bony plates along its back.

Stegosaurus grew to about 6.5 meters (21 feet), but some reached 9 meters (30 feet). Its forelimbs were much shorter than its hind limbs, giving its back an arched appearance. The feet were short and broad. Two pairs of pointed bony spikes were present on the end of the tail, which were likely defensive weapons. The plates along the back may have been a temperature-regulating system.
2 Britannica Sources
1. stegosaur
2. Stegosaurus
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
When and where did Stegosaurus live?
Stegosaurus lived during the Late Jurassic Period, approximately 159 million to 144 million years ago. Their fossils have been discovered in various locations, including North America, Africa, Europe, and Asia. Notably, the Stegosaurus genus, which includes the species S. sulcatus, S. ungulatus, and S. stenops, was excavated from the Morrison Formation in Utah, U.S.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What did Stegosaurus eat and how did it get its food?
Stegosaurus was a herbivorous dinosaur that lived during the Late Jurassic Period. It ate plants, but its weak dentition indicates that it likely fed on plants that did not require much preparation by the teeth.

Because of its low build, paleontologists believe Stegosaurus likely fed on low shrubbery. Stegosaurus had a small, long, low, and narrow skull, with little space for sizable jaw muscles. The weak dentition consisted of small, laterally compressed, leaf-shaped teeth arranged in short, straight rows. It is possible that bacteria in its digestive tract helped break down the cellulose-rich Jurassic plant tissues. Although none have been discovered in Stegosaurus specimens, gastroliths, or stomach stones, may have aided its digestion.
2 Britannica Sources
1. Stegosaurus
2. dinosaur: The plant eaters
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why did Stegosaurus have plates and spikes on its body?
The Stegosaurus, a plated dinosaur from the Late Jurassic Period, is known for its distinctive plates and spiked tail.

The arrangement and purpose of the plates have been subjects of various hypotheses. While it was initially believed that the plates served as protection for the backbone and spinal cord, new discoveries indicate that the plates alternated along the spine. The presence of numerous blood vessels in the plates supports the theory that they functioned for thermoregulation, either releasing body heat or collecting it from the sun.

Two pairs of bony spikes on the tail are thought to have served as defensive weapons or possibly for display. The exact function of these features remains uncertain, but display and species recognition are likely possibilities.
1 Britannica Source
1. Stegosaurus
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do scientists study and learn about Stegosaurus today?
Scientists study Stegosaurus by analyzing fossil remains found worldwide, including in North America, Africa, Europe, and Asia. These studies involve reexamining existing specimens and considering new discoveries to understand the dinosaur's characteristics.

Paleontologists investigate the arrangement and purpose of the Stegosaurus's plates, initially believed to be protective. The discovery of blood vessels in the plates led to the hypothesis that they served for thermoregulation, either releasing heat or collecting it like solar panels. Researchers also study the Stegosaurus's tail spikes, presumed to be defensive weapons.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Stegosaurus, (genus Stegosaurus), genus various plated dinosaurs (Stegosauria) of the Late Jurassic Period (159 million to 144 million years ago) recognizable by its spiked tail and series of large triangular bony plates along the back. Stegosaurus usually grew to a length of about 6.5 metres (21 feet), but some reached 9 metres (30 feet). The skull and brain were very small for such a large animal. The forelimbs were much shorter than the hind limbs, which gave the back a characteristically arched appearance. The feet were short and broad. The genus is made up of three species—S. sulcatus, S. ungulatus, and S. stenops—all of which were excavated from the Morrison Formation, Utah, U.S.

Various hypotheses have attempted to explain the arrangement and use of the plates. Paleontologists had long thought that Stegosaurus had two parallel rows of plates, either staggered or paired, and that these afforded protection to the animal’s backbone and spinal cord. However, new discoveries and reexamination of existing Stegosaurus specimens since the 1970s suggest that the plates alternated along the backbone, as no two plates from the same animal have exactly the same shape or size. Because the plates contained many blood vessels, the alternating placement appears consistent with a hypothesis of thermoregulation. This hypothesis proposes that the plates acted as radiators, releasing body heat to a cooler ambient environment; conversely, the plates could also have collected heat by being faced toward the sun like living solar panels.

Two pairs of pointed bony spikes were present on the end of the tail. These are presumed to have served as defensive weapons, but they may have been ornamental. The spinal cord in the region of the sacrum was enlarged and was actually larger than the brain, a fact that gave rise to the misconception that Stegosaurus possessed two brains. It is more likely, however, that much of the sacral cavity was used for storing glycogen, as is the case in many present-day animals.

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Stegosaurus and its relatives are closely related to the ankylosaurs, with which they share not only dermal armour but several other features, including a simple curved row of small teeth. Both groups evolved from a lineage of smaller armoured dinosaurs such as Scutellosaurus and Scelidosaurus of the Early Jurassic Period (206 million to 180 million years ago). Stegosaurs lost the armour from the flanks of the body that these early relatives had. Plating among different stegosaurs varied: some forms apparently had parallel rather than alternating plates, and some, such as Kentrurosaurus, had plates along the front half of the back and spikes along the back half and tail. These variations cast doubt on the hypothesis of a strong thermoregulatory function for the plates of Stegosaurus, because such structures were not optimized in all stegosaurs for collecting or releasing heat. Furthermore, it is puzzling why other stegosaurs and other dinosaurs lacked elaborate thermoregulatory structures. Display and species recognition remain likely functions for the plates, although such hypotheses are difficult to investigate.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by John P. Rafferty.

Stegosaurus

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