Ornithopods are a suborder of ornithischian dinosaurs that had a beak, a two-legged walk or a two-legged and four-legged walk, and no body armor. These plant-eating dinosaurs lived from the late Triassic period until the Cretaceous period.

Ornithopods had no hole in the outer, lower jaw. Ornithopods included:

• Heterodontosaurids - small, early dinosaurs with three kinds of teeth
• Hypsilophodontids - small, fast-running dinosaurs with self-sharpening teeth and a small beak
• Dryosaurids - small, fast-running dinosaurs with a long, stiff tail
• Thescelosaurids - late, fast-running dinosaurs
• Camptosaurids - beaked dinosaurs with hoof-like claws
• Iguanodontids - beaked dinosaurs with hoof-like claws and a spike on each thumb
• Hadrosaurids - large duck-billed dinosaurs with no head crest
• Lambeosaurids - large duck-billed dinosaurs with a head crest

Anatotitan:

Anatotitan was a large, duck-billed dinosaur about 33 feet (10 m) long and 8 feet (2.5 m) tall at the hips; it weighed roughly 5 tons (7300 kg) - about as big as a bus. It was very similar to Edmontosaurus, but it was more lightly built and had longer legs. Anatotitan had short arms, a long, pointy tail, three hoofed toes, mitten-like hands, a flat, sloping head with a wide, toothless beak, cheek pouches, and hundreds of closely-packed cheek teeth (for grinding plant material).Anatotitan was a biped (it walked on two legs) but it could also walk on four legs, perhaps to graze low-lying plants. Anatotitan was probably a relatively slow-moving dinosaur with few defenses, but may have had keen senses (eyesight, hearing, and smell) to help it avoid predators.Anatotitan lived in the late Cretaceous period, about 70-65 million years ago, toward the end of the Mesozoic Era.T. rex and Dromaeosaurus were among its contemporaries, and they may have preyed upon Anatotitan.Anatotitan may have lived in herds, like many other hadrosaurs.Anatotitan was an herbivore, a plant eater. It probably ate conifer needles, twigs, seeds, and other plant material with its tough beak. It had no teeth in its beak, but had hundreds of cheek teeth used for grinding up the tough plant material that it ate. Anatotitan had three rows of replaceable teeth for a total of 720 teeth - it a tooth broke off, another replaced it.

Parasaurolophus:

Parasaurolophus was a long-crested, duck-billed dinosaur. Its extremely long, backwards-leaning, hollow, bony crest was as bigger than the rest of its skull and may have been used to produce a low-frequency, foghorn-like sound, enhance its sense of smell, and/or used in courtship displays. The Parasaurolophus' nostrils (at the end of its snout) went up through the crest and back down it, forming four tubes. The crest was up to 6 feet (1.8 m) long. Its snout was narrow and shorter than other hadrosaur snouts. There may have been sex differences in the length of the crest; males may have had longer crests. Parasaurolophus also had a notch in its back, right where the crest would touch the back when its head leaned backwards.

Parasaurolophus grew to be about 40 ft (12 m) long and 8 feet (2.8 m) tall at the hips. It weighed about 2 tons. It had pebbly-textured skin, a spoon-shaped beak, and a pointy tail. It may have had webbed fingers, giving it a mitten-like hand, but some paleontologists argue that the web-like fossilized hands are an artifact of the fossilization process. Its sight and hearing were keen, but it had no natural defenses. It had a toothless, horny beak and numerous cheek teeth.

Parasaurolophus may have been a herding animal; it may have migrated from shorelines to higher ground to reproduce. There is no evidence that Parasaurolophus spent much time in the water. It used to be thought that its crest was used as a snorkel-like device, indicating that the animal spent much time in the water, but since the crest has no nostril at the top, this theory has been dismissed. Also, fossilized stomach contents have been found, consisting mostly of land plants. Again, this indicates that Parasaurolophus spent most of its time on land.Parasaurolophus lived during the late Cretaceous period, about 76-65 Million years ago, toward the end of the Mesozoic, the Age of Reptiles. Among the contemporaries of Parasaurolophus in the late-Cretaceous (in North America) were Albertosaurus, Nanotyrannus, Lambeosaurus (another hadrosaur), Euoplocephalus, Kritosaurus, and Pachyrhinosaurus.Parasaurolophus was an herbivore, eating pine needles, leaves, and twigs. Fossilized stomach contents have been found, consisting mostly of land plants.

Dryosaurus:

Dryosaurus was about 10 feet (3 m) long, 5 feet (1.7 m) tall at the hips, and weighed about 170-200 pounds (77-90 kg). It had large eyes, long, thin legs with three toes, much shorter arms with five long fingers, a horny beak, a toothless upper front jaw, and self-sharpening cheek teeth. It may have stored food in its cheeks. It had a long neck and a stiff tail used for balance.Dryosaurus was an herbivorous ornithischian dinosaur, belonging to the Suborder Ornithopoda, and Family Hypsilophodontidae. Dryosaurus lived in lush forest during the late Jurassic period to the late Jurassic Period, about 156 to 145 million years ago. Its contemporaries were Apatosaurus, Diplodocus, Brachiosaurus, Coelurus, Allosaurus, Stegosaurus, and Ceratosaurus.Dryosaurus laid eggs and may have cared for their young for at least a little while. This is evidenced by eggs found carefully placed in other Hypsilophodontid nests. It may have traveled in herds. This horny beaked dinosaur was an herbivore (it ate only plants) that lived in lush forest habitats. Dryosaurus may have stored food in its cheeks.

Hypsilophodon:

Hypsilophodon measured about 6.5 feet long (2 m) and 2 feet (0.6 m) tall, weighing about 150 pounds (68 kg). Hypsilophodon had a beak made of horn, cheek pouches and 28-30 self-sharpening cheek teeth in a small skull 4 3/4 inches (12 cm) long, by 2 inches (5 cm) wide. Hypsilophodon may have had 2 rows of bony plates running down its back.

Slender legs and a stiffened tail gave it speed and agility. It had large eyes, strong jaws, five-fingered hands and four-toed feet (one toe on each foot had a hind claw). Hypsilophodon was a very fast bi-pedal (two-legged) runner; its back legs were long. It had a stiffened tail that helped it balance when running. Hypsilophodon lived in the early Cretaceous Period, about 125-120 million years ago. This horny beaked dinosaur was an herbivore (it ate only plants). It had 28-30 chisel-like teeth.

Ouranosaurus:

Ouranosaurus was a sail-backed, plant-eating, iguanodontid dinosaur from the early Cretaceous period. It was about 24 feet (7 m) long and may have weighed about 4 tons.Ouranosaurus' sail was formed by long-spined vertebrae in the backbone. The spines stuck out from its back and tail; the spines were covered with skin. The sail was probably used for temperature regulation in the hot, African environment. It would help the animal cool down in the heat of day, by dispersing extra heat when the sail was turned away from the sun. It would also help Ouranosaurus collect heat early in the morning when the sail faced the sun. The sail may also have been used for mating displays, interspecies rivalry, or to make it look larger when confronting predators. Ouranosaurus had few defenses.Ouranosaurus' skull was longer than other iguanodontid skulls. It had a bit of a crest on its snout, two bony bumps. Ouranosaurus had a flat, wide, toothless beak, and many cheek teeth for grinding plant material. The neck was short and flexible. There were five short fingers on each hand. The second and third fingers had hoof-like nails that Ouranosaurus probably used when it went on all four limbs to graze low-lying plants. Each thumb had a small conical spike like Iguanodon.Ouranosaurus lived in the early Cretaceous period, about 115-110 million years ago. Spinosaurus, a large, sail-backed meat-eater, was one of its contemporaries in the hot, Cretaceous environment of North Africa.Ouranosaurus was an ornithopod, whose intelligence was midway among the dinosaurs. Ouranosaurus was an herbivore, a plant eater. It probably ate leaves, fruit, seeds, and other plant material with its tough beak. It had no teeth in its beak, but had many cheek teeth that it used for grinding up tough plant material.

Camptosaurus:

Camptosaurus (meaning "bent lizard") was a plant-eater from the late Jurassic period (about 156 to 145 million years ago) that looked a lot like Iguanodon. It was a heavy ornithischian dinosaur that was about 16-23 feet (5-7 m) long and 3-4 feet (1 m) high at the hips, weighing roughly 2,200 pounds (1000 kg). It had a long snout, hundreds of teeth and a horny beak. Its legs were longer than its arms; it had four-toed feet and five-fingered arms, all with hooves. It could walk on two or four legs; it probably went on all four to graze for low-lying plants. Camptosaurus lived in the late Jurassic period, about 156-145 million years ago.Camptosaurus may an its arms; it had four-toed feet and five-fingered arms, all with hooves. It could walk on two or four legs; it probably went on all four to graze for low-lying plants. Camptosaurus lived in the late Jurassic period, about 156-145 million years ago.Camptosaurus may have lived in herds.Camptosaurus was an herbivore, a plant eater. It probably nipped cycads and other prehistoric plants with its tough, toothed beak. It had no teeth in the front of its mouth, but had strong teeth in the side of its jaw (cheek teeth) to grind the plant material.

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