Known colloquially as stegosaurs, the Stegosauria are a group of herbivorous dinosaurs of the Jurassic and Early Cretaceous Periods, being found mostly in the Northern Hemisphere, predominantly in what is now North America and China.
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.
All stegosaurs have rows of special bones, called osteoderms
, which develop into plates and spines along the back and tail. Many also have intermediate ones, called 'splates'.
They had characteristic long, narrow heads and a horn-covered beak or rhamphotheca
, which covered the front of the upper jaw (premaxillary) and lower jaw (predentary) bones. Similar structures are seen in turtles
. Apart from Huayangosaurus
, stegosaurs subsequently lost nearby premaxillary teeth.
All are quadrupedal
, with hoof-like toes on all four limbs. All stegosaurians after Huayangosaurus
have forelimbs much shorter than their hindlimbs. Given that their speed would have been limited by their shortest limb and their size is likely to have precluded them from being bipedal
, this suggests that they were not able to run quickly.
was originally named as an order within Reptilia by O.C. Marsh
in 1877, although today it is generally treated as an infraorder or suborder (or simply a clade
) within Thyreophora
, the armored dinosaurs
. It includes the families Huayangosauridae
The Huayangosauridae were an early family of stegosaurs which lived during the early to middle Jurassic Period. In general, 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 Stegosaurian dinosaurs thus far recovered being to the Stegosauridae, which lived in the later part of the Jurassic and early Cretaceous. It includes the well-known Stegosaurus. The family is widespread, with members across the Northern Hemisphere and Africa.
Following is a list of stegosaurian genera by classification and location:
of the Denver Museum of Nature and Science
published a preliminary phyletic tree of stegosaurs, in the 2001 description of Hesperosaurus
. Here, the basal stegosaur Huayangosaurus
is used as the outgroup. The Stegosauridae
are then defined as all stegosaurs closer to Stegosaurus
than to Huayangosaurus
. The position of Chungkingosaurus
is uncertain due to lack of data.
`--S. ungulatus (=?S. armatus)
To date, several genera from China bearing names have not been formally described, including "Changdusaurus
" and "Yingshanosaurus
". Until formal descriptions are published, these genera are regarded as nomina nuda
- Fastovsky DE, Weishampel DB (2005). The Evolution and Extinction of the Dinosaurs (2nd Edition). Cambridge University Press. ISBN 0-521-81172-4.