By | September 9, 2016

The woodlands of the Jurassic Period teemed with massive, four-legged plant-eaters called stegosaurs. Members of the stegosaur family often had defensive spikes on their tails and shoulders, and rows of bony plates ran along their backs. The purpose of the plates is a mystery, but they may have been used for display or temperature control.


Key features
■ Double row of plates or spikes along the neck, back, and tail
■ Narrow head
■ Beaklike tip of mouth
■ Hooflike toes
■ Walked on all fours

Stegosaurs lived from 176 million years ago (Middle Jurassic) to 100 million years ago (Early Cretaceous).


Each shoulder had a large spike. Pairs of smaller spikes lined the tail. The spikes probably helped ward off attackers.

Stegosaurus (STEG-oh-SORE-uss)


When: 150–145 million years ago (Late Jurassic)

Fossil location: USA, Portugal

Habitat: Woodland

Length: 30 ft (9 m)

Diet: Plants

Large, diamond-shaped plates ran along the back of this famous dinosaur. Although the plates would have made Stegosaurus look bigger and more fearsome, they were no good as armor. It’s more likely they evolved for use in social or courtship displays. Stegosaurus had a toothless beak made of a hornlike substance. At the back of its mouth were rows of teeth that it used to crush leaves, chewing them to a pulp with simple up-and-down movements.



Stegosaurus’s skeleton

This skeleton gives Stegosaurus an arched appearance, but in reality it probably held its head and tail erect, creating a more horizontal profile.

Huayangosaurus (HWAH-YANG-oh-SORE-uss)


When: 165 million years ago (Middle Jurassic)

Fossil location: China

Habitat: River valleys

Length: 13 ft (4 m)

Diet: Ferns, leaves, cycad fruit

One of the early stegosaurs, Huayangosaurus differed from later species in having a shorter, broader snout, with teeth at the front of its top jaw. All four legs were about the same length, whereas other stegosaurs have long hind legs and short front legs.

Tuojiangosaurus (TOO-YANG-oh-SORE-uss)


When: 160–150 million years ago (Late Jurassic)

Fossil location: China

Habitat: Forests

Length: 23 ft (7 m)

Diet: Plants

Scientists have found remarkably complete fossils of Tuojiangosaurus, a close relative of Stegosaurus that lived in China. The bony plates along its back and hips were tall and triangular, whereas those on its neck were much smaller. Like other stegosaurs, it had vicious spikes at the tip of the tail, allowing it to gore enemies or rivals with a violent lash of the tail.

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