Temporal range: Middle Jurassic – Lower Cretaceous, 176–100 mya
|Fossil skeleton of a Stegosaurus,
National Museum of Natural History
The Stegosaurs were a group of dinosaurs in the suborder Thyreophora. They have small heads, peg-like teeth and vertical bony plates and spines on their back and tail. They flourished from the Upper Jurassic to the Lower Cretaceous.
The Stegosauria was originally named as an order within Reptilia (Saurischia) by O.C. Marsh in 1877. Now it is treated as an infraorder or suborder (or simply a clade) within Thyreophora, the armoured dinosaurs. It includes the families Huayangosauridae and Stegosauridae.
The Huayangosauridae were an early family of stegosaurs which lived during the Middle Jurassic. They were smaller than later stegosaurs and had shorter and higher skulls. Currently, the only confirmed genus included is the type genus Huayangosaurus of China. The poorly-known remains of Regnosaurus from England, however, indicate it too could be a member. Its lower jaw is very similar to the former.
The vast majority of stegosaurs being to the Stegosauridae, found in the later part of the Jurassic and the early Cretaceous. It includes the well-known Stegosaurus. The family is widespread, with members across the Northern Hemisphere and Africa.
- Family Huayangosauridae
- Family Stegosauridae
- Chialingosaurus – (Sichuan, China)
- Chungkingosaurus – (Chongqing, China)
- Dacentrurus – (England, France & Spain)
- Hesperosaurus – (Wyoming, USA)
- Miragaia – (Portugal) 
- Monkonosaurus – (Tibet, China)
- Paranthodon – (South Africa)
- Wuerhosaurus – (Xinjiang, Western China)
- Kentrosaurus – (Tanzania, Africa)
- Lexovisaurus  – (England & France)
- Stegosaurus – (Wyoming, USA)
- Tuojiangosaurus – (Sichuan, China)
- ?Craterosaurus – (Bedfordshire, England)
- Jiangjunosaurus – (Xinjiang, Western China)
- Marsh O.C. 1877. New order of extinct Reptilia (Stegosauria) from the Jurassic of the Rocky Mountains. American Journal of Science, 14(ser.3):513-514.
- Mateus, Octávio; Maidment, Susannah C.R.; and Christiansen, Nicolai A. (2009). "A new long-necked 'sauropod-mimic' stegosaur and the evolution of the plated dinosaurs" (pdf). Proceedings of the Royal Society B: Biological Sciences 276 (1663): 1815–21. doi:10.1098/rspb.2008.1909. PMC 2674496. PMID 19324778. http://rspb.royalsocietypublishing.org/content/early/2009/02/21/rspb.2008.1909.full.pdf+html.
- Maidment, Susannah C.R.; Norman, David B.; Barrett, Paul M.; and Upchurch, Paul (in press). "Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)". Journal of Systematic Palaeontology 6 (04): 367. doi:10.1017/S1477201908002459.