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Ohmdenosaurus it was a long-necked, plant-eating dinosaur from the early Jurassic period, about 191 million years before

Oligosaurus is a little, plant-eating dinosaur from the late Cretaceous era.

Omeisaurus was a very long-necked plant-eating dinosaur from the late Jurassic era, about156-145 million years back.

Omnivores it is an animals that eat both animals and plants.

Opisthocoelicaudia it means "hollow-backed tail (vertebrae)" was a sauropod dinosaur that lived during the late Cretaceous era

Orcomimus it was meat-eating, bipedal dinosaur, an advanced theropod that lived throughout the late Cretaceous period, approximately 84-65 million years ago.

Order The dinosaurs are divided into two orders: saurischia und ornithischia.

Oreodonts were the most ordinary hoofed herbivorous (plant-eating) mammals in North America during the Oligocene (from about 35-5 million years back).

Ornatotholus it was plant-eating, thick-skulled bipedal dinosaur that lived throughout the late Cretaceous period, approximately 84-71 million years ago.

Ornithischia an organize of the dinosaurs.

Ornithocheirus it was a large pterodactyloid pterosaur, a flying reptile that lived during the Cretaceous era.

Ornithodira is the clad which includes dinosaurs (as well as their early ancestors the lagosuchians) and pterosaurs. They contain s-shaped necks.

Ornithopods are a suborder of ornithischian dinosaurs that have no hole in the surface, lower jaw and a long pubis that extends beyond ahead than the ilium

Orthoceras were ancient types of nautiloids that looked like squid with a stretched, straight (or slightly curved), conical, chambered, and wrinkled shell.

Ostrich a large flightless bird accomplished of running at high speeds

Othnielia was a ornithopod dinosaur from the late Jurassic era, about 156 to 145 million years back.

Ouranosaurus it was a sail-backed, plant-eating, Ornithischian dinosaur.

Overburden it is the rock that lies on top of a fossil.

Oviraptor was a theropod dinosaur among a parrot-like head, toothless beak, long fingers, and long legs.