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Dino Index


9 meters

4 meters

4.5 metric



Ste – go – sore – us



The stegosaurus swung his tail, and SMASH! the little brachiosaur was struck down by the spikes in the stegosaurus’ tail. These dinosaurs have never been known for their intelligence and in fact they gave the whole dinosaur – equals – stupid image. Othniel Charles Marsh founda good skull and used it to make a cast of the dinosaur’s brain. It was about 80g. compared to a 4.5 metric tonne body, this seemd impossibly small, and from then on dinosaurs were all thought of as having small brains and being stupid. (They really gave dinosaurs a bad name!)

It was in a narrow canyon browsing on vegetation when the brachiosaur came by. The stegosaurus was not very smart, and decided running dinosaurs are dangerous, so it defended itself. In fact, the small sauropod (the brachiosaurus) was running from REAL danger: a pair of allosaurs coming up the valley.

They come around the corner shortly and find our protagonist the stegosaur right in the middle of their path. Go hunting for baby brachiosaurs, and find a full grown stegosaur. What do you do? Do what the pair of allosaurs did… give up and go home.

That is a better alternative than dealing with the sharp spikes on the end of the tail. And besides, the plates on his back were filling with blood and getting red. This made a scary sight.

The above blue text is a description of events in a popular dinosaur movie Walking With the Dinosaurs.

The stegosaurus was the largest of the stegosaurians. This stegosaurian had triangular plates along the back in two rows. The exact purpose of the plates isnot known with 100% certainty but there are a fewstrong theories.

  1. The plates are a way for Stegosaurus to control body temperature. In hot environments, blood is sent to these plates. The large surface area (they are big!) allows the clood to cool off quickly and easily. In hot environments, the blood vessels to these plates close to keep the valuable heat in the body.
  2. The plates serve for defense. They may fill with blood and take a reddish color, alerting predators to the danger that lies behind them: the great spiked tail that stegosuarus used for defense.
  3. The Plates were used for identification or of part of courtship – to attract a mate so they could make babies. This seems to be a lesser theory.

The plates were arranged in two rows, we are fairly certain, but whether they alternated from one side to the other down the back, or
were arranged in even pairs is not clear although the alternating pattern seems more likely.

What did they eat?

They were vegetarians. But they did not graze on low level grasses, since the grasses didn’t evolve until the late cretaceous, when the stegosaurs were already very extinct. They probably foraged on low growing plants, about one meter up, since that is the level of their heads while they walked. Perhaps their diet included mosses, ferns, horsetails, cycads, and conifers. But if they could raise themselves up on their hind legs, they could have eaten and browsed plants up to 6 meters.

Their teeth had small horizontal wear facets, that indicate they couldn’t really chew food properly. They swallowed gastroliths (stones that would stay in their digestive system and help them grind plants) since their teeth were not very good at breaking down food in their mouth.

Stegosaurus has been found in several locations in Western North America: Colorado, Wyoming, and Utah. In 2006, a confirmed finding of stegosaurus from Europe (Portugal) was made. At least three species have been found in the Morrison Formation. There is some evidence that they were herd animals. This comes from track that have been found by Matthew Mossbrucker of the Morrison Natural History Museum from Colorado. One set of tracks shows four or five baby stegosaurs. Another track has juvenile footprints with adult footprints (track) crossing over them.

While they are not that tall, there is a suggestion that they could raise themselves up on their hindlimbs (back legs, standing). this would make their effective height as much as 9 m tall! Of course, we don’t really know if they could do this but it would make a big difference to their height.

We are quite certain that even if they could stand, they would not be able to walk in that stance.

The tail spikes

Were they just for show, or real defense?

The tail was quite flexible – more flexible than many other dinosaurs, so the tail could swing fairly easily. And the front legs probably could move easily so the stegosaurus could swivel to get the tail closer to hit other dinosaurs (predators). Finally, lots of tail spikes show damage. That means they probably were used in defense to strike other dinosaurs.

In fact, one allosaurus fossil shows a hole in one of the tail bones that a stegosaurus spike could fit into perfectly. Perhaps the stegosaurus was really able to make a good defense with this large siked tail after all.

Stegosaurs became the state dinosaur in Colorado in 1982. They are well recognized and somewhat popular, appearing in comics,


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