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STEG-o-sore-us                 STEGOSAURUS                     [Roofed Lizard]
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     Stegosaurus lived during the Jurassic Period, 144 to 213 million years
ago.  Actually, stegosauria is the name for many different types of dinosaurs
that ate plants and had hard, bony plates on their backs.  The Stegosaurus
weighed about five tons and sometimes stood on its hind legs to eat the leaves
from the top of trees.
     The first Stegosaurus skeleton was found by Professor Marsh of Yale in
1878.  He also discovered that the Stegosaurus had a second "brain," called 
the sacral brain, located between the dinosaur's hip sockets.  The Stegosaurus 
did not use his second brain to think but rather to control its massive hind 
legs and great spiked tail.  Other large-tailed dinosaurs, like the 
Brontosaurus (Apatosaurus), also had a sacral brain, but the Stegosaurus
had the largest.
     The Stegosaurus had to defend itself against the giant meat-eaters of
the Late Jurassic Period like Allosaurus, Ceratosaurus and Euparkeria which
grew up to forty five feet long and weighed as much as four tons. With its
sacral brain the Stegosaurus could quickly whip its spike-studded tail at
attackers.  The long spikes were covered with horn and were very sharp.
     The Stegosaurus' tiny front legs and far-forward center of gravity let
the dinosaur rapidly turn about when under attack.  Dr. Robert T. Bakker
recently suggested that the Stegosaurus could raise and lower the triangular
plates on his back to counter attacks from above or from the sides.
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