MEANING: Roof lizard
PERIOD: Late Jurassic
CONTINENT: North America
Stegosaurus is an armored ornithischian dinosaur from the Late Jurassic of what is now North America. It was a large heavily built quadruped, characterized by distinctive kite-shaped plates running down the length of its back. The tail had four large spikes extending from the tip, which are thought to have been used as defense against predators. The large plates may have been used for display, and possibly thermoregulation as well. Stegosaurus had small head relative to its body size, and most likely fed on bushes and shrubs. It could reach up to 7.5 m in length, and weighed around 5 t.
Stegosaurus is from the Jurassic. The Jurassic is a geologic period that spanned from the end of the Triassic, 201 million y ears ago, to the beginning of the Cretaceous, 145 million years ago. It is the middle period of the Mesozoic Era. The start of the Jurassic was marked by the major Triassic-Jurassic extinction event. The end, however, has no clear boundary with the Cretaceous. By the beginning of the Jurassic, Pangea had begun rifting into two landmasses: Laurasia and Gondwana, and the climate was warm with no ice caps. Life on land was dominated by dinosaurs, and the first birds appeared, evolving from a branch of theropods. The oceans were inhabited by marine reptiles, while pterosaurs were the dominant flying vertebrates.
Stegosaurus is a stegosaurian. Stegosauria is a group of herbivorous ornithischian dinosaurs that lived mainly during the Jurassic period, though there are some members known from the early Cretaceous. Stegosaurian fossils have been found mostly in the Northern Hemisphere.
Stegosaurians were armored dinosaurs; together with the ankylosaurs, they make up a larger group known as the thyreophorans. An early evolutionary innovation was the development of spikes as defensive weapons. Over time, these developed into much larger plates and spikes as the species within the group grew to larger size. These plates usually tend to run in two rows down the back, and end as spikes, known as thagomizers, at the tip of the tail.
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