Stegosaurus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of armored

Thyreophora

The Thyreophora were a subgroup of the ornithischian dinosaurs...

 stegosaurid

Stegosauria

Known colloquially as stegosaurs, the Stegosauria are a group of herbivorous dinosaurs of the Jurassic and Early Cretaceous Periods, being found mostly in the Northern Hemisphere, predominantly in what is now North America and China....

 dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

. They lived during the Late Jurassic

Late Jurassic

The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

 period (Kimmeridgian

Kimmeridgian

In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....

 to early Tithonian

Tithonian

In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...

), some 155 to 150 million years ago in what is now western North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. In 2006, a specimen of Stegosaurus was announced from Portugal

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, showing that they were present in Europe as well. Due to its distinctive tail spikes

Thagomizer

Thagomizer is an informal name for the distinctive arrangement of four to ten spikes on the tails of stegosaurid dinosaurs. These spikes are believed to have been a defensive measure against predators.-Paleobiology:...

 and plates, Stegosaurus is one of the most recognizable dinosaurs. At least three species have been identified in the upper Morrison Formation

Morrison Formation

The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...

 and are known from the remains of about 80 individuals.

A large, heavily built, herbivorous

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

 quadruped

Quadruped

Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...

, Stegosaurus had a distinctive and unusual posture, with a heavily rounded back, short forelimbs, head held low to the ground and a stiffened tail held high in the air.