Stegosauridae

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Stegosauridae
Temporal range: Middle Jurassic - Early Cretaceous, 170–100Ma
Stegosaurus BW.jpg
Life restoration of Stegosaurus stenops
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Stegosauria
Superfamily: Stegosauroidea
Family: Stegosauridae
Marsh, 1880
Type species
Stegosaurus stenops
Marsh, 1877

Stegosauridae is a family of thyreophoran dinosaurs comprising all stegosaurs more closely related to Stegosaurus than to Huayangosaurus.[1] Their fossil range's extent into the late Early Cretaceous exceeds that of other stegosaurs, such as huayangosaurids, which had died out by the end of the Late Jurassic. They are characterized by rows of osteoderms along the top of their neck, trunk and tail which graded with varying abruptness from the anterior plates to the thagomizers at a point posterior to the dorsal vertebrae.[2] These may have had a number of functions: display and/or thermoregulation for the broad flat osteoderms, defense for the spikes.[3][4][5]

Paleobiology[edit]

Comparison among three well-known stegosaurids

General anatomy[edit]

Stegosaurids were usually large and powerful dinosaurs. Their front legs were shorter than their rear making them slow-moving dinosaurs. When Othniel Charles Marsh first found Stegosaurus, he portrayed the genus with very short front legs and neck. But new evidence shows that they had relatively long body parts.[6] Several species show sexual dimorphism in the sacrum with the putative female having an extra pair of sacral ribs. There are also two sizes of parascapular spines in Lexovisaurus which can be ascribed to such variation.[3][7]

Bite[edit]

In 2010 Míriam Reichel, using the 3D-modelling software ZBrush, created two digital models of Stegosaurus teeth differing in the presence or not of serrations. She proved that Stegosaurus had rhamphotheca.[dubious ] She also found that stegosaurs were capable of shearing small branches, and suggested that the same data could be applied to other stegosaurids.[8]

Evolution[edit]

In contrast with early stegosaurs, like Huayangosaurus, stegosaurid skulls are shallower and the difference between the long hindlimb and short forelimb larger.[2] The osteoderms of stegosaurids can attain a large size either as the broad plates of Stegosaurus or the long spikes of Kentrosaurus.[6]

Classification[edit]

Taxonomy[edit]

Stegosauridae is usually divided into two main subfamilies: Dacentrurinae and Stegosaurinae.[9] Stegosaurinae are usually characterized by large sizes. The earliest stegosaur is thought to be Lexovisaurus[10] from the Bathonian of England. There was found a massive femur of the juvenile Lexovisaurus.

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

Suborder Thyreophora

Infraorder Stegosauria

Basal Stegosaurids[edit]

Like basal stegosaurs, stegosaurids of such a persuasion, like Lexovisaurus, Kentrosaurus or Tuojiangosaurus, are characterized by the comparatively large osteoderms running along their backs and reduced lateral osteoderms. Contrasting with the abrupt transition from plate to spike in stegosaurines, primitive stegosaurids have their plates grade into spines in a zone with osteoderms showing an intermediate shape.[2][14]

Dacentrurinae[edit]

Proposed by Mateus et al. (2009) to include Dacentrurus and all stegosaurs closer in relation to it than to Stegosaurus. Currently, only one other member of Dacentrurinae is known: Miragaia.[13][15] They usually have long back spines and necks.

Stegosaurinae[edit]

First recognized by Nopcsa in 1915, it comprises according to the definition of Sereno (1998) the eponymous Stegosaurus and all stegosaurs more closely related with it than to Dacentrurus. Besides the type, it includes Hesperosaurus and Wuerhosaurus.[1]

Phylogeny[edit]

A cladogram by paleontologist Kenneth Carpenter.[16]

Stegosauridae

?Chungkingosaurus




Chialingosaurus





Wuerhosaurus




Dacentrurus



Hesperosaurus






Tuojiangosaurus





Kentrosaurus



Lexovisaurus[17]





Stegosaurus stenops



S. ungulatus (=?S. armatus)








Carpenter's proposal states that Wuerhosaurus and Hesperosaurus are more closely related to Tuojiangosaurus and Dacentrurus than to Stegosaurus. However, Thomas Holtz[dubious ] has proposed that Hypsirophus, Stegosaurus, Hesperosaurus and Wuerhosaurus form a subfamily-Stegosaurinae:[9]

Stegosauridae
Dacentrurinae

Dacentrurus



Miragaia



Stegosaurinae


Wuerhosaurus



Hesperosaurus





Stegosaurus



Hypsirophus





Timeline of genera[edit]

Cretaceous Jurassic Triassic Late Cretaceous Early Cretaceous Late Jurassic Middle Jurassic Early Jurassic Late Triassic Middle Triassic Early Triassic Wuerhosaurus Craterosaurus Paranthodon Stegosaurus Monkonosaurus Miragaia (dinosaur) Tuojiangosaurus Hesperosaurus Kentrosaurus Chungkingosaurus Chialingosaurus Dacentrurus Lexovisaurus Cretaceous Jurassic Triassic Late Cretaceous Early Cretaceous Late Jurassic Middle Jurassic Early Jurassic Late Triassic Middle Triassic Early Triassic

References[edit]

  1. ^ a b Galton, Peter; Paul Upchurch (2004). "16: Stegosauria". In David B. Weishampel, Peter Dodson , Halszka Osmólska. Dinosauria (2nd ed.). Berkeley: University of California Press. p. 358. 
  2. ^ a b c Sereno, Paul C. (1999-06-25). "The Evolution of Dinosaurs". Science 284 (5423): 2137–2147. doi:10.1126/science.284.5423.2137. PMID 10381873. 
  3. ^ a b Galton, Peter; Paul Upchurch (2004). "16: Stegosauria". In David B. Weishampel, Peter Dodson , Halszka Osmólska. Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 361–362. 
  4. ^ Hayashi, Shoji; Kenneth Carpenter; Mahito Watabe; Lorrie A. Mcwhinney (2011). "Ontogenetic Histology of Stegosaurus Plates and Spikes". Palaeontology (The Palaeontological Association) 55 (1): 145–161. doi:10.1111/j.1475-4983.2011.01122.x. 
  5. ^ "Stegosaur plates used for identification". National Geographic website. National Geographic News. 25 May 2005. Retrieved 2006-10-26. 
  6. ^ a b Galton, Peter (1997). "21: Stegosaurs". In James O. Farlow, M. K. Brett-Surman. The Complete Dinosaur. Bloomington: Indiana University Press. ISBN 9780253213136. 
  7. ^ Barden, Holly E.; Maidment, Susannah C. R. (May 2011). "Evidence for sexual dimorphism in the stegosaurian dinosaur Kentrosaurus aethiopicus from the Upper Jurassic of Tanzania". Journal of Vertebrate Paleontology 31 (3): 641–651. doi:10.1080/02724634.2011.557112. 
  8. ^ Reichel, Miriam (2010). "A model for the bite mechanics in the herbivorous dinosaur Stegosaurus (Ornithischia, Stegosauridae)". Swiss Journal of Geosciences 103 (2): 235–240. doi:10.1007/s00015-010-0025-1. 
  9. ^ a b c Thomas R. Holtz, Jr. (2007). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages. Random House. 
  10. ^ Peter M. Galton and H. Philip Powell. "Stegosaurian Dinosaurs from the Bathonian(Middle Jurassic) of England, the earliest record of the family Stegosauridae". 
  11. ^ Maidment, Susannah C.R.; Norman, David B.; Barrett, Paul M.; Upchurch, Paul (2008). "Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)". Journal of Systematic Palaeontology 6 (4): 367. doi:10.1017/S1477201908002459. 
  12. ^ M.L. Casanovas Cladellas. Dacentrurus armatus (Stegosauria, Dinosauria) del Cretácico inferior de los Serranos (Valencia, España). 
  13. ^ a b Mateus, Octávio; Maidment, Susannah C.R.; 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. 
  14. ^ Sereno, Paul C.; Zhimin, Dong (1992). "The skull of the basal stegosaur Huayangosaurus taibaii and a cladistic diagnosis of stegosauria". Journal of Vertebrate Paleontology 12 (3): 318–343. doi:10.1080/02724634.1992.10011463. 
  15. ^ J.I.Ruiz-Omeñaca. "New stegosaurian (Ornithischia, Thyreophora) remains from Jurassic-Cretaceous transition beds of Valencia province (Southwestern Iberian Range, Spain)". 
  16. ^ 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.
  17. ^ Galton, Peter M. (September 1985). "British plated dinosaurs (Ornithischia, Stegosauridae)". Journal of Vertebrate Paleontology 5 (3): 211–254. doi:10.1080/02724634.1985.10011859.