Stegosaurus

## *Stegosaurus ungulatus*

### Description

Herbivorous dinosaur with large bony plates along its curved shape back and four spikes on the end of the tail

## Physiology

### Attributes

17 large plates on its back; four, long, powerful thagomizer on its tail; very small brain; able to flush blood into plates; small head

### Height

4.32 m (14.16 ft; at the hips)5.23 m (17.15 ft; at tallest plate)

## Biography

### Discovery

1879

***Stegosaurus*** (name meaning "*Roofed Lizard*") is a genus of stegosaurid dinosaur that originated during the Late Jurassic period in what is now North America. The largest of all stegosaurs, standing around 5 meters tall, measuring 11 meters long, and weighing 7 tons, *Stegosaurus* is one of the world's most recognizable dinosaurs, famous for the large plates on its back and the lethal spikes on its tail.

## Facts

### Era & Discovery

*Stegosaurus* lived in western North America during the Late Jurassic period from 155 to 145 million years ago. It shared its environment with *Allosaurus*, *Ceratosaurus*, *Ornitholestes*, *Brachiosaurus*, *Diplodocus*, *Apatosaurus*, *Camarasaurus*, *Dryosaurus*, *Nanosaurus*, and *Anurognathus*.

*Stegosaurus* remains were first identified during the "*Bone Wars*" in 1879 by Othniel Charles Marsh at Dinosaur Ridge National Landmark. The first known skeletons were fragmentary and the bones were scattered, and it would be many years before the true appearance of these animals, including their posture and plate arrangement, became well understood. When O.C. Marsh described the first fossil of a *Stegosaurus*, he concluded that the plates would have lain flat on its back. After finding a specimen that had been covered with mud, which had held the plates in place, Marsh realized that they stood vertically, alternately on either side of the spine.

Since its discovery, *Stegosaurus* has become one of the most well-known and easily-identifiable dinosaurs in the world.

### Physical Attributes

The largest member of the Stegosaur family of dinosaurs, a race of herbivorous dinosaurs armed with plates and spikes, *Stegosaurus* stood 14 feet (4.3 m) tall at the hips (17 feet (5.2 m) at the tallest plate), measured 36 feet (11 m) in length, and weighed 7 tons. Paleontologists have claimed that no animal living today looks even remotely like *Stegosaurus*. Compared with the rest of its body, *Stegosaurus* had a small but long, cone-shaped head with relatively small eyes and a blunt beak for a mouth. The hind limbs of *Stegosaurus* were thick and were far larger than its front limbs. Some scientists believe that the back legs of *Stegosaurus* were designed for rearing up to reach the tops of trees. It also had an arch-shaped back. *Stegosaurus* is also known for its remarkably tiny brain, at only 80 grams (around the size of a plum), apparently sufficient for its needs.

#### Plates (Osteoderms)

Down the vertebrae of *Stegosaurus* rising vertically along its arched back were a distinctive double row of 17 to 22, large, kite-shaped, spinal plates (or osteoderms) which ran down its neck until near the end of its tail. Each plate had a root-like pattern. The function of the plates of *Stegosaurus* has been much debated, as scientists are not exactly sure what the plates were used for. They may have warned off predators, or allowed members of the same species to recognized each other.

Initially thought of as some form of defense mechanism, another suggestion researchers have also proposed is that the plates were used to help comtrol/regulate body temperature. Wind tunnel tests have suggested that the plates are well shaped to gather and dissipate heat. There are tiny grooves in the plate surfaces, possibly where blood vessels would have been. The amount of blood passing through these vessels would determine the amount of heat transfer.

#### Spikes (Thagomizers)

Near the tip of its tail were two pairs of long, sharp, lethal spikes (known as thagomizers) extending horizontally near the end of its tail. The spikes were slightly curved in shape. This made *Stegosaurus* different from its relative *Kentrosaurus*, who had paired spikes throughout the entire length of its tail and on its back. *Stegosaurus* tails were without question one of the greatest as well as most dangerous weapons ever evolved by a plant-eating animal. Such a weapon appears necessary considering *Stegosaurus* coexisted with large predatory theropod dinosaurs, such as the fearsome *Allosaurus*. With those spikes measuring three feet in length, roughly as long as a baseball bat, *Stegosaurus* could wield them with devastating effect. Some *Stegosaurus* skeletons had six to eight spikes instead, possibly as a birth defect or by genetic chance or a combination of both.

### Behavior & Traits

*Stegosaurus* was both a social and solitary dinosaur, getting together with other members of its kind during mating season, but also traveling with other members of its kind when needed. Trackways show that the animal likely traveled in multi-age herds for protection. However, *Stegosaurus* was considerably dangerous, despite being a herbivorous dinosaur.

## Trivia

* The sound effects of *Stegosaurus* are that of bull, camel, elephant, lion, walrus, and other dinosaur sounds.