Stegosaurus: Armored Jurassic Dinosaur

Stegosaurus is one of the most famous dinosaurs and surely one that has embedded itself in popular culture. This large, armored herbivore lived during the late Jurassic Period in the lush forests that had been created by the high sea levels, warm climate, and abundant rain. Fossils of stegosaurus have been found worldwide, with the most specimens located in North America.

Stegosaurus was the largest of the family of herbivorous dinosaurs that shared a name with it, the stegosaurs. It was around thirty-five feet long, nine feet tall, and weight about three and a half tons. It had a broad, fan-shaped body, short columnar legs to support its weight, and a tiny head. Its back legs were longer than its front legs, much like a plateosaur of the Triassic Period and its head was held lower than its tail. One of the most commonly-cited features about stegosaurus is the size of its brain. The famous comparison has been made between its brain and a walnut. Although stegosaurus wasn't exactly high intelligence, it didn't exactly need it given the array of natural defenses it possessed.

Stegosaurus had seventeen diamond-shaped bony plats running down the length of its back in two rows. These plates may have served a number of purposes. The first was to protect the back of the herbivore from predator attacks. The second was that they could have been used as a heat regulation device much like the sails of Permian pelycosaurs. The final possible function was display, either to confuse predators or to attract mates during courtship. The plates might have served all three of these functions, but scientists can only speculate with the fossils that are available to them.

In addition to these plates, stegosaurus had pairs of meter-long spikes on its tail. This could have made a devastating weapon if swung at a potential attacker. It might have even been enough of an effective deterrent to stop most predators from attacking stegosaurus in the first place. Thus, given its natural defenses, stegosaurus did not need to devote much of its brain to dealing with predators and could go about its business of eating. Also, the fact that stegosaurus was probably quite slow (judging by leg morphology) was one that would not have mattered much given these armored adaptations.

Stegosaurus had a toothless beak at the end of its skull which it used to snip vegetation off of low shrubs and ferns. There is some speculation that stegosaurus could have reared up on its back legs in order to reach choice leaves on trees, but this is open to debate. Inside its mouth were chisel-shaped teeth used to chop the vegetation into chunks before swallowing it. It might have made use of gastroliths to compensate for the fact that it could not chew its food like later ornithischian dinosaurs did.

Stegosaurus disappeared by the end of the Jurassic, probably due to the change in climate that accompanied the Cretaceous Period. The vast, lush forests it had depended on were shrinking as the weather became hotter and drier.