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One of the most easily recognized dinosaurs of the Late Jurassic Period, the genus name Stegosaurus comes from Greek words meaning "roof lizard," referring to the belief by 19th-century paleontologists that its distinguishing plates lay flat along its back like shingles on a roof.


The flat triangular plates which give the Stegosaurus its name extended from its neck to its tail, which at the tip was armed with two to four pairs of pointed spikes up to 4 feet long. The plates were up to 3 feet tall (with the tallest being on the hips), several inches thick at the base where they attached to the body, and thin and narrow at the tips. Covered with skin that had many blood vessels in it, paleontologists believe that the plates helped the animal dissipate heat. It is also likely that the plates provided some protection against predators, and they may also have played a role in courtship rituals.

The front legs of Stegosaurus were only half as long as the heavy rear legs, but they were stout and well suited for carrying the weight of the front of the body. The feet were short and stubby, with four blunt toes on the front feet and three toes on the rear feet. The difference in size between the front legs and rear legs suggests that the ancestors of Stegosaurus walked on its hind legs.

The largest member of the armored dinosaur family, Stegosaurus was up to 30 feet long, 10 feet tall at the hips, and weighed up to 6,800 pounds. Its relatively tiny head "housed" a brain no larger than that of a modern dog.

Dentition and skull structure show that Stegosaurus was an herbivore, and its "stooped" posture suggests that it was limited to eating plants no more than 3 feet tall. Its diet probably included ferns, mosses, cycads, fruits, conifers, and horsetails.

The first Stegosaurus fossil was found in Colorado in 1876 by M. P. Felch, and was named by Othniel C. Marsh in 1877. The most complete Stegosaurus yet found (nicknamed Spike) was discovered near Canon City, Colorado, in 1992 by Bryan Small, Tim Seeber, and Kenneth Carpenter, and it was this find that proved that Stegosaurus's plates actually stood up along its back rather than lay flat. Fossils from about 80 individuals were discovered in the Morrison Formation, which is centered in Wyoming and Colorado but reaches into Montana, North Dakota, South Dakota, Nebraska, Kansas, the panhandles of Oklahoma and Texas, New Mexico, Arizona, Utah, and Idaho. Most of the fossils discovered to date have been adults, but a juvenile specimen was discovered in 1994 in Wyoming. Although no true Stegosaurus fossils have been found outside of western North America, close relatives have been found in Western Europe, southern India, China, and southern Africa.

. Stegosaurus is the state fossil of Colorado, in tribute to the number of dinosaur skeletons found in the state.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Reptilia
order Ornithischia
suborder Thyreophora
family Stegosauridae


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The Robinson Library >> Paleontology

This page was last updated on 09/28/2018.