Stegosaurus lived in theUpper Jurassic period around 155 to 145 million years ago. It is one of the most easily recognized dinosaurs, with its distinctive double row of kite-shaped plates on its back, and the long spikes on its tail. The armor was necessary as it lived with such meat-eaters asAllosaurus andCeratosaurus.
Stegosaurus was originally named byOthniel Charles Marsh in 1877,[1] from fossils found nearMorrison,Colorado. These first bones became the firstspecies of Stegosaur named:Stegosaurus armatus.
Several differentStegosaurus species have been found.
Stegosaurus armatus: This was the first type ofStegosaurus to be found. Over thirty different skeletons have been discovered by scientists. This type had four tail spikes and small plates. At 9 meters (30 ft), it was the longest species ofStegosaurus.
Stegosaurus stenops: Named by Marsh in 1887,[2] it was discovered nearCañon City, Colorado, in 1886. This is the best known species ofStegosaurus, mainly because its fossils make at least one complete skeleton. It had large, broad plates and four tail spikes.S. stenops is known from at least 50 partial skeletons of both adults and juveniles, one complete skull and four partial skulls. It was shorter thanS. armatus, at 7 m (23 ft).
Stegosaurus longispinus: This type of Stegosaur is known from one incomplete skeleton.S. longispinus had a set of very long tail spines. LikeS. stenops, it grew to 7 m (23 ft) in length.
S. ungulatus: Named by Marsh in 1879 from remains recovered atComo Bluff,Wyoming,[3] it is only known from a few backbones and armor plates. It is probably the same asS. armatus.
S. sulcatus: This is another partial skeleton. It is probably the same asS. armatus.
S. duplex: This animal is probably the same asS. armatus. It was also named by Marsh in 1887,.[2] Its fossils were found in 1879 by Edward Ashley atComo Bluff,Wyoming.
?S. seeleyanus: Probably the same asS. armatus.
?S. (Diracodon) laticeps: Named by Marsh in 1881 from some jawbone fragments.[4]
Stegosaurus was the largeststegosaur, reaching up to 12 m (39.4 ft) in length and weighing up to 5,000 kg (5.5 short tons). However, 7 to 9 m was a more usual length.
Theskull ofStegosaurus was long and narrow. Because of its short front legs, its head was close to the ground, probably no higher than 1 m (3.3 ft). It ate low-growing plants because of this. It had no front teeth, but it did have a horn-covered beak. Stegosaurian chewing teeth were small and triangular and did little grinding as they lacked wear surfaces.[5]
Unlike most dinosaurs, it did not have a lacuna (hole) in its skull between the nose and eye.[6]
It has often been said that theStegosaurus brain was the size of awalnut. Actually, it had a brain several times the size of a walnut. The bundle of nerves near the base of the tail that controlled reflexes in the back of the body was larger than the brain and is sometimes said to be a "second brain". These issues are discussed inDinosaur brains and intelligence.
Stegosaurus had very short forelimbs in relation to its hind legs. The back legs each had three short toes, while the front legs had five toes. All four limbs were supported by pads behind the toes.[6]
↑2.02.1Marsh OC (1887). "Principal characters of American Jurassic dinosaurs, part IX. The skull and dermal armour ofStegosaurus".American Journal of Science.3 (34):413–417.
↑Fastovsky DE, Weishampel DB (2005). "Stegosauria:Hot Plates". In Fastovsky DE, Weishampel DB (ed.).The Evolution and Extinction of the Dinosaurs (2nd ed.). Cambridge University Press. pp. 107–130.ISBN0521811724.
↑6.06.1Lambert D (1993).The Ultimate Dinosaur Book. Dorling Kindersley, New York. pp. 110–129.ISBN156458304X.
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