Movies - Stegosaurus

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Stegosaurus (pronounced ) meaning "roof-lizard", because of the plates on its back (Greek stego = plate/roof + sauros = lizard) was a genus of large herbivorous dinosaurs from the Upper Jurassic of North America. It is among the most easily identifiable dinosaurs, due to the distinctive double row of kite-shaped plates along the animal's back (the basis for its scientific name) and the long spikes on its tail (referred to as the thagomizer).

Characteristics

Stegosaurus was the largest stegosaur, reaching up to 12 meters (40 feet) in length and weighing up to 5,000 kg (5.5 short tons). However, most specimens never exceeded 7 meters (23 feet) and 2,000 kg (2 short tons).

The plates of Stegosaurus were highly modified osteoderms, or bony-cored scales, similar to those seen in crocodiles and many lizards today. The largest plates were found over the animal's hips and measured 60 centimeters (2 feet) wide and 60 centimeters tall. The arrangement of the plates has long been a subject of debate, but most paleontologists now agree that they formed a pair of alternating rows down the animal's back.

The purpose of the plates is also debated. Their large size suggests that they may have been used to increase the apparent height of the animal in order to intimidate enemies or to impress other members of the species. However, the plates were fragile and ill-placed for defensive purposes, and both male and female specimens had them. A more recent theory proposes that they may have helped to control the temperature of the animal, much as elephants and jackrabbits do with their ears. The plates had blood vessels running through grooves and wind flowing around the plates would have cooled the blood. The temperature-control theory has recently been discounted, since the closest relative to the common plate-wielding species, Stegosaurus stenops, had low surface area spikes instead of plates, implying that cooling was not important enough to require specialized structural formations such as plates. A study published in 2005 points to a simpler purpose: identification. Researchers also believe this may be the purpose behind other unique formations found in various dinosaur species. The tail appears to have acted as a weapon. Its tail included four to eight spikes (four in S. stenops, eight in S. armatus), each about 2 to 3 feet long, an arrangement known as a thagomizer. Discoveries of articulated stegosaur armor show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted.

The skull of Stegosaurus was long and narrow, and its head was carried close to the ground, probably no higher than 1 meter (3 feet). Stegosaurus had a small brain, about the size of a walnut.

Relationships

Stegosaurus was a member of the armored dinosaurs, or Thyreophora, a suborder which includes the ankylosaurs and other stegosaurs, such as the huayangosaurids, Wuerhosaurus, and Kentrosaurus.

Species

A number of Stegosaurus species have been identified, though many of these have been considered invalid or synonymous with existing species by most scientists .

Stegosaurus armatus ("armored roof lizard"): The first species to be found, currently known from two partial skeletons, two partial skulls, and at least 30 fragmentary individuals. This species had eight horizontal tail spikes and relatively small plates. At 9 meters (30 ft), it was the longest species of Stegosaurus.
Stegosaurus stenops ("narrow-faced roof lizard"): The most well-known species of Stegosaurus, it had large, broad plates and four tail spikes. S. stenops is known from at least 50 partial skeletons of both adults and juvelines, one complete skull, and four partial skulls. It was shorter than S. armatus, at 7 meters (23 ft) long. At least one paleontologist (Gilmore) does not consider this a species of Stegosaurus, instead placing it in the genus Diracodon. Others (such as Bakker) disagree.
Stegosaurus longispinus ("long-spined roof lizad"): Known from one partial skeleton. S. longispinus is notable for its set of four unusualy long tail spines. Some consider it a species of Kentrosaurus. Like S. stenops, it grew to 7 meters (23 ft) in length.

Dubious species:

?S. ungulatus ("hoofed roof lizard"): Known from a few vertebrae and armor plates; probably the same as S. armatus.
?S. sulcatus ("furrowed roof lizard"): Partial skeleton, probably the same as S. armatus.
?S. duplex ("two-level roof lizard"): Probably the same as S. armatus.
?S. seeleyanus: (originally Hypsirophus). Probably the same as S. armatus.
?S. (Diracodon) laticeps: Just as some consider S. stenops a species of Diracodon, others consider Diracodon itself to be a species of Stegosaurus. If this is the case, it is most likely synonymous with S. stenops.

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Movies - Stegosaurus

Characteristics

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Species

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