Stegosauria

Stegosauria Temporal range: Middle Jurassic to Early Cretaceous 169–100Ma PreЄ Є O S D C P T J K Pg N Possible Toarcian, Aalenian and Late Maastrichtian records in the form of fossil tracks and referred fossils.
Stegosaurus armatus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
clade:	Dinosauria
Order:	†Ornithischia
Suborder:	†Stegosauria Marsh, 1877
Superfamily:	†Stegosauroidea Marsh, 1880
Subgroups
†Craterosaurus? †Gigantspinosaurus †Amargastegos †Jiangjunosaurus †Huayangosauridae †Stegosauridae

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. Stegosaurs appeared in the Middle Jurassic, around 165 mya ago and died out in the Early Cretaceous, about 125 mya ago.

Paleobiology

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
           └──┬──Tuojiangosaurus
              └──┬──┬──Kentrosaurus            
                 │  └──Lexovisaurus
                 └──┬──Stegosaurus stenops
                    └──S. ungulatus (=?S. armatus)

Species

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 S. 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.

By the Mid Cretaceous, however, stegosaurs seem to have gone extinct, Wuerhosaurus being the last of the stegosaurs known, dying out in the Early Cretaceous.