Stegosaurus

StegosaurusStegosaurus — Stegosaurus is a genus of stegosaurid armoured dinosaur from the Late Jurassic period (Kimmeridgian to Early Tithonian) in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, suggesting that they were present in Europe as well. Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs, along with Tyrannosaurus, Triceratops, and Apatosaurus. The name Stegosaurus means “roof-lizard” and is derived from the Greek stegos (“roof”) and sauros (“lizard”). At least three species have been identified in the upper Morrison Formation and are known from the remains of about 80 individuals. They lived some 155 to 145 million years ago, in an environment and time dominated by the giant sauropods Diplodocus, Camarasaurus, and Apatosaurus.

A large, heavily-built and herbivorous quadruped, Stegosaurus had a distinctive and unusual posture, with a heavily-arched back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Its array of plates and spikes have been the subject of much speculation. The spikes were most likely used for defense, while the plates have also been proposed as a defensive mechanism, as well as having display and thermoregulatory (heat control) functions.

Stegosaurus was the largest of all the stegosaurians (bigger than genera such as Kentrosaurus and Huayangosaurus) and, although roughly bus-sized, it nonetheless shared many anatomical features (including the tail spines and plates) with the other stegosaurian genera.

Stegosaurus was the largest stegosaur, reaching up to 12 meters (39 ft) in length and possibly weighing up to 5,000 kilograms (5.5 short tons). However, 7 to 9 metres was a more usual length. Soon after its discovery, Marsh considered Stegosaurus to have been bipedal, due to its short forelimbs. He had changed his mind however, by 1891, after considering the heavy build of the animal. Although Stegosaurus is undoubtedly now considered to have been quadrupedal, there has been some discussion over whether it could have reared up on its hind legs, using its tail to form a tripod with its hind limbs and browsing for higher foliage. This has been proposed by Bakker and opposed by Carpenter.

Stegosaurus did have very short forelimbs, in relation to its hind legs. Furthermore, within the hind limbs, the lower section (comprising the tibia and fibula) was short compared with the femur. This suggests that it couldn’t walk very fast, as the stride of the back legs at speed would have overtaken the front legs, giving a maximum speed of 6–7 kilometers per hour (4–5 mi/hr).

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