One of the most famous dinosaurs due to the spectacular array of bony plates which ran the whole length of its back and tail, Stegosaurus was alive in North America in the late Jurassic Period, 160-145 million years ago. Its name means "Covered Lizard". It weighed approximately 7 tonnes fully grown, and reached lengths of around 12 metres. Even though it was herbivorous, like many plant-eating dinosaurs (see Triceratops) it had nasty ways of warding off predators, including four metre-long spikes on the end of a short and very muscular tail.
The function of the bony plates has been endlessly debated, with some paleontologists feeling that they may have served as a mating display, and others proposing that Stegosaurus lowered them to cover its flanks when attacked, or even that they were a means of controlling the animal's body temperature by offering more of a surface for the sun to heat. Current opinion is that they served dual functions as a display: both for attracting mates and for warding off large carnivores by making the animal seem bigger.
The first stegosaur fossil was discovered in 1877 by the unfortunately named M.P. Felch. Recent CGI film appearances include Jurassic Park II: The Lost World.
Sources/Links:
Walking With Dinosaurs (BBC): http://www.bbc.co.uk/dinosaurs/fact_files/scrub/stegosaurus.shtml
Smithsonian Natural Museum: http://www.nmnh.si.edu/paleo/dino/stegnew.htm
www.stegosaurus.org - "Home of the Coolest Dinosaur ! The official Stegosaurus website. Ask any dinosaur !"
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