Temporal range: Middle Jurassic - Early Cretaceous
Known colloquially as stegosaurs, the Stegosauria is a group of herbivorous ornithischian dinosaurs that lived from the Middle Jurassic to the Early Cretaceous, being found in Asia (China), North America, Africa and Europe. Their geographical origins are unclear; the earliest stegosaurs have been found in China, although fragmentary material hails from southern England. The genus Stegosaurus, from which the group acquires its name, is by far the most famous stegosaurian. Stegosaurids appeared in the Middle Jurassic, around 165 mya ago and died out in the Early Cretaceous, about 125 mya ago.
All stegosaurs have rows of special bones, called osteoderms, which develop into plates and spines along the back and tail (forming the so-called "thagomizer"). Many also have intermediate spines, called 'splates'.
Stegosauria ├──Huayangosaurus └──Stegosauridae └──┬─?Chungkingosaurus └──┬──Chialingosaurus └──┬──┬──Wuerhosaurus │ └──┬──Dacentrurus │ └──Hesperosaurus └──┬──Tuojingaosaurus └──┬──┬──Kentrosaurus │ └──Lexovisaurus └──┬──Stegosaurus stenops └──S. ungulatus (=?S. armatus)
There are numerous stegosaur genera and species know. The oldest and most basal member of the Stegosauria for which good material is known, Huayangosaurus, comes from the Middle Jurassic of China (about 166 mya). Other younger stegosaur genera that are also known from China are Chungkigosaurus, Chialingosaurus, Tuojiangosaurus and Gigantspinosaurus. European stegosaurs from the same time as these Chinese specimens are Lexovisaurus and Loricatosaurus, although Lexovisaurus is considered by some as a nomen dubium.
In the Late Jurassic, the stegosaurs went through a big radiation: in Europe, Miragaia and Dacentrurus are known; in the United States, there are Stegosaurus (although a Stegosaurus stenops individual was also found in Portugal), Hesperorsaurus and Alcovasaurus (the holotype for this genus has been lost and many uncertainties have risen regarding the validity of this genus); in Africa Kentrosaurus is known from numerous specimens; and from China Jiangjunosaurus has been discovered.
In the Cretaceous, however, stegosaurs seem to have gone exctinct, Wuerhosaurus being the last of the stegosaurs known (it lived during the Early Cretaceous).