Thyreophora

Stegosauria

Huayangosaurus: Found in China during the Middle Jurassic, these animals had small plates in skin, with spike-like armor and equal length front and rear legs; they were approximately 13 feet (4 meters) long, with short snouts; they are considered the most primitive of the stegosaurs.

Stegosaurus: A Late Jurassic dinosaur weighing approximately one to two tons; it had an array of bony plates along the length of the back and tail spikes; the hind legs were long, and the forelegs were short and massive; the head was small and elongated, and the brain size was extremely small for an animal of this size. More than 80 specimens have been uncovered in the United States’ Morrison formation.

Kentrosaurus: This dinosaur (the name means “pointed lizard”) had spines on its tail, hip, shoulder, and back; its bony plates, similar to those on Stegosaurus, were also present on the neck and anterior part of the back. It measured close to 13 feet (4 meters) long and may have been more flexible than its close relative, the Stegosaurus.

Ankylosauria

Sarcolestes: This dinosaur (“flesh robber”) developed in the Middle Jurassic period, and is thought to be one of the earliest ankylosaurs. It had a large piece of armor-plating on its outer surface and when found in the late 1800s, was first thought to be a flesh-eating dinosaur—thus its name.

Dracopelta: The Dracopelta (“armored dragon”) was a small, Late Jurassic period ankylosaur from Portugal. There are few fossil remains, thus its size is only estimated to be around 6 feet (2 meters) in length.

Neornithischia

Ornithopoda

Camptosaurus: Called “bent lizard,” this beaked dinosaur was a medium-sized, bipedal herbivore that lived in the Late Jurassic to Early Cretaceous periods. It reached lengths up to 26 feet (7.9 meters) and was 6.7 feet (2 meters) tall at the hip. It is also thought to be the ancestor to many of the highly successful, plant-eating dinosaurs in the Cretaceous period.

Heterodontosaurus: This dinosaur was only about 3 feet (1 meter) in length. It had canine-like teeth and relatively long arms, with large hands; its teeth were designed for cutting.

Marginocephalia

Ceratops: This dinosaur (meaning “horn face”) was a ceratopsian that lived in the Late Cretaceous period. Fossils of this creature are found in the United States in Montana, as well as in Alberta, Canada. It is famous for the horn that sticks out from the middle of its “forehead” and above the nose.