Stegosauria

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Stegosaurians
Temporal range: Middle Jurassic - Early Cretaceous, 176–100Ma
Fossil skeleton of a Stegosaurus,
National Museum of Natural History
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Eurypoda
Suborder: Stegosauria
Marsh, 1877
Superfamily: Stegosauroidea
Marsh, 1880
Type species
Stegosaurus stenops
Marsh, 1877
Subgroups

Craterosaurus?
Gigantspinosaurus
Jiangjunosaurus
Huayangosauridae
Stegosauridae

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.

Paleobiology[edit]

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'.[dubious ]

Skull[edit]

They had characteristic long, narrow heads and a horn-covered beak or rhamphotheca,[1] which covered the front of the upper jaw (premaxillary) and lower jaw (predentary) bones. Similar structures are seen in turtles and birds. Apart from Huayangosaurus, stegosaurs subsequently lost nearby premaxillary teeth.[2]

Posture[edit]

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.

The front feet of stegosaurs are commonly depicted in art and in museum displays with fingers splayed out and slanted downward. However, in this position most bones in the hand would be disarticulated. In reality, the hand bones of stegosaurs were arranged into vertical columns, with the main fingers forming a tube-like structure. This is similar to the hands of sauropod dinosaurs, and is also supported by evidence from stegosaur footprints and fossils found in a lifelike pose.[3]

Trace fossils[edit]

Stegosaur tracks were first recognized in 1996 from a hindprint-only trackway discovered at the Clevland-Lloyd quarry, which is located near Price, Utah.[4] Two years later, a new ichnogenus called Stegopodus was erected for another set of stegosaur tracks which were found near Arches National Park, also in Utah.[4] Unlike the first, this trackway preserved traces of the forefeet. Fossil remains indicate that stegosaurs have five digits on the forefeet and three weight-bearing digits on the hind feet.[4] From this scientists were able to predict the appearance of stegosaur tracks in 1990, six years in advance of the first actual discovery of Morrison stegosaur tracks.[4] More trackways have been found since the erection of Stegopodus. None, however, have preserved traces of the front feet and stegosaur traces remain rare.[4]

Evolutionary history[edit]

Like the spikes and shields of ankylosaurs the bony plates and spines of stegosaurs evolved from the low-keeled osteoderms characteristic of basal thyreophorans.[5] One such described genus, Scelidosaurus is proposed to be morphologically close to the common ancestor of the clade uniting stegosaurs and ankylosaurs, Eurypoda.[6]

Classification[edit]

History[edit]

Stegosauria was originally named as an order within Reptilia by O.C. Marsh in 1877,[7] 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 and Stegosauridae.

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 belong 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, Africa and possibly South America.[8]

The following timeline shows the date of descriptions for valid stegosaur genera beginning in 1824, when the first non-avian dinosaur was formally described.

21st century in paleontology 20th century in paleontology 19th century in paleontology 2090s in paleontology 2080s in paleontology 2070s in paleontology 2060s in paleontology 2050s in paleontology 2040s in paleontology 2030s in paleontology 2020s in paleontology 2010s in paleontology 2000s in paleontology 1990s in paleontology 1980s in paleontology 1970s in paleontology 1960s in paleontology 1950s in paleontology 1940s in paleontology 1930s in paleontology 1920s in paleontology 1910s in paleontology 1900s in paleontology 1890s in paleontology 1880s in paleontology 1870s in paleontology 1860s in paleontology 1850s in paleontology 1840s in paleontology 1830s in paleontology 1820s in paleontology Huayangosaurus Regnosaurus Chialingosaurus Chungkingosaurus Dacentrurus Hesperosaurus Miragaia (dinosaur) Paranthodon Wuerhosaurus Kentrosaurus Lexovisaurus Stegosaurus Tuojiangosaurus Craterosaurus Jiangjunosaurus Gigantspinosaurus 21st century in paleontology 20th century in paleontology 19th century in paleontology 2090s in paleontology 2080s in paleontology 2070s in paleontology 2060s in paleontology 2050s in paleontology 2040s in paleontology 2030s in paleontology 2020s in paleontology 2010s in paleontology 2000s in paleontology 1990s in paleontology 1980s in paleontology 1970s in paleontology 1960s in paleontology 1950s in paleontology 1940s in paleontology 1930s in paleontology 1920s in paleontology 1910s in paleontology 1900s in paleontology 1890s in paleontology 1880s in paleontology 1870s in paleontology 1860s in paleontology 1850s in paleontology 1840s in paleontology 1830s in paleontology 1820s in paleontology

Taxonomy[edit]

A fossil melee involving a stegosaurian (Tuojiangosaurus) and a mid-sized theropod (Monolophosaurus), Field Museum in Chicago

Following is a list of stegosaurian genera by classification and location:


Phylogeny[edit]

Kenneth Carpenter of the Denver Museum of Nature and Science published a preliminary phyletic tree[11] 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.

Undescribed species[edit]

To date, several genera from China bearing names have been proposed but not formally described, including "Changdusaurus" and "Yingshanosaurus".[12] Until formal descriptions are published, these genera are regarded as nomina nuda.

References[edit]

  1. ^ Galton, Peter; Paul Upchurch (2004). "16: Stegosauria". In David B. Weishampel, Peter Dodson , Halszka Osmólska. Dinosauria (2nd ed.). Berkeley: University of California Press. p. 361. 
  2. ^ Sereno, P & Z-M Dong (1992). The skull of the basal stegosaur Huayangosaurus taibaii and a cladistic diagnosis of Stegosauria. Journal of Vertebrate Paleontology 51: 318-343
  3. ^ Senter, P. (2010). "Evidence for a sauropod-like metacarpal configuration in stegosaurian dinosaurs." Acta Palaeontologica Polonica, in press.
  4. ^ a b c d e "Walk and Don't Look Back: The Footprints; Stegosaurs" in Foster, J. (2007). Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pg. 238
  5. ^ Norman, David (2001). "Scelidosaurus, the earliest complete dinosaur" in The Armored Dinosaurs, pp 3-24. Bloomington: Indiana University Press. ISBN 0-253-33964-2.
  6. ^ Galton, Peter (1997). "21: Stegosaurs". In James O. Farlow, M. K. Brett-Surman. The Complete Dinosaur. Bloomington: Indiana University Press. ISBN 9780253213136. 
  7. ^ 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.
  8. ^ Pereda-Suberbiola, Xabier; Galton, Peter M.; Mallison, Heinrich; Novas, Fernando (2013). "A plated dinosaur (Ornithischia, Stegosauria) from the Early Cretaceous of Argentina, South America: an evaluation". Alcheringa: An Australasian Journal of Palaeontology 37 (1): 65–78. doi:10.1080/03115518.2012.702531. 
  9. ^ 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. 
  10. ^ Maidment, Susannah C.R.; Norman, David B.; Barrett, Paul M.; and Upchurch, Paul (2008). "Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)". Journal of Systematic Palaeontology 6 (4): 367. doi:10.1017/S1477201908002459. 
  11. ^ Carpenter, K., Miles, C.A., and Cloward, K. (2001). "New Primitive Stegosaur from the Morrison Formation, Wyoming", in Carpenter, Kenneth(ed) The Armored Dinosaurs. Indiana University Press. ISBN 0-253-33964-2, 55–75.
  12. ^ Maidment, Susannah C.R.; Guangbiao Wei (2006). "A review of the Late Jurassic stegosaurs (Dinosauria, Stegosauria) from the People's Republic of China". Geological Magazine 143 (5): 621–634. doi:10.1017/S0016756806002500. 
  • Fastovsky DE, Weishampel DB (2005). "Stegosauria:Hot Plates". In Fastovsky DE, Weishampel DB. The Evolution and Extinction of the Dinosaurs (2nd Edition). Cambridge University Press. pp. 107–130. ISBN 0-521-81172-4. 

External links[edit]