From Academic Kids


Conservation status: Fossil

Missing image

Fossil skeleton,

National Museum of Natural History

Scientific classification

?S. affinis
S. armatus (type)
?S. discurus
S. laticeps
?S. longispinus
?S. madagascariensis
?S. seeleyanus
?S. stenops

Stegosaurus was a large herbivorous dinosaur genus from the Upper Jurassic of North America. It is among the most easily identifiable dinosaurs, owing to the distinctive double row of kite-shaped plates along the back and the four long spikes on the tail. Its name is derived from the plates, and means "roofed" or "covered lizard" in Greek. It is one of the most popular dinosaurs in children's fiction.


Stegosaurus is the largest stegosaur, and reached up to 12 meters (40 feet) in length, and 5,000 kg (5.5 short tons) in mass, though most species never exceeded 7 meters (23 feet), and about 2,000 kg (2 short tons).

The largest plates, over the hips, were 60 centimeters (2 feet) wide and 60 centimeters tall. The arrangement of the plates has long been a subject of debate, but most scientists now agree that the plates form a pair of alternating rows down the back. The plates are highly modified osteoderms, or bony-cored scales, similar to those seen in crocodiles and many lizards.

The purpose of the plates is debated. Their large size suggests that they may have been used to increase the apparent height of the animal, to intimidate enemies or impress other members of the species, although both male and female members have plates, and they were fragile and ill-placed if for defensive purposes. A more recent theory is that they may have helped to control the temperature of the animal, much as elephants and jackrabbits do with their ears. The plates have blood vessels running through grooves. Wind flowing around the plates would have cooled the blood flowing through them. The temperature-control theory has recently been discounted, since the closest relative to the common plate-wielding species, Stegosaurus stenops, had low surface area spikes instead of plates, implying that cooling was not important enough to require specialized structural formations such as plates. A study published in 2005 points to a simpler purpose: identification. Researchers also believe this may be the purpose behind other unique formations found in various dinosaur species. [1] (

The tail appears simply to have acted as a weapon.

The skull of Stegosaurus was long and narrow, and its head was carried close to the ground, probably no higher than 1 meter (3 feet).


Stegosaurus was a member of the armored dinosaurs, or Thyreophora. Relatives include Ankylosaurus and Nodosaurus.


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