It isn't hard to imagine the world full of dinosaurs, even though these extinct animals haven't walked the earth for millions of years. Learn all about dinosaurs, including early dinosaur discoveries, dinosaur fossils, and dinosaur extinction.

The Joint Polish-Mongolian Paleontological Expeditions of the 1960s produced many new kinds of dinosaurs, many of which were small theropods. One of these theropods was a Elmisaurus. Learn more about Elmisaurus.

In 1980 is altangerel Perle named Erlikosaurus andrewsi after the demon Erlik from Mongolian mythology and paleontologist Roy Chapman Andrews. It was closely related to Segnosaurus. Learn more about the Erlikosaurus.

Euoplocephalus lived at the same time and in the same areas as Edmontonia. Euoplocephalus roamed the forests cropping low plants with its broad beak. It probably ate any type of plant it came across. Learn about Euoplocephalus, Late Cretaceous dinosaurs and dinosaurs of all eras.

Gallimimus ("chicken mimic") was the largest of the ornithomimids (the "ostrich dinosaurs") known. It has been found only in the Late Cretaceous Nemegt Formation of Mongolia. Learn more about the Gallimimus and other Late Cretaceous dinosaurs.

Garudimimus brevipes was one of many dinosaurs found by the Joint Soviet-Mongolian Paleontological Expeditions of the 1970s. It was named for the Garuda bird of Hindu mythology; its name means "short-footed Garuda mimic."

The flat-headed Goyocephale was one of the most unusual pachycephalosaurs. It was found by the Joint Polish-Mongolian Paleontological Expeditions to the Gobi Desert is and was named and described in 1982. Learn more about the Goyocephale.

Hadrosaurus ("thick reptile") was the first hadrosaur skeleton to be discovered. It was named and described in 1858 by Joseph Leidy, the father of American paleontology.

Named after the flying mythical Greek creatures called Harpies that snatched victims with their hands, Harpymimus ("snatcher mimic") is the most primitive ornithomimid known. Learn more about the Harpymimus and other Late Cretaceous dinosaurs.

As its name ("even head") suggests, Homalocephale had a flat head unlike most pachycephalosaurs. It is known from limited but very good material. The single skull of Homalocephale is missing the front of the snout but is otherwise complete. Learn more about the Homocephale.

The head of Hypacrosaurus looked much like Corythosaurus. The snout was somewhat ducklike is although the nostrils were in slightly different places. Learn more about the Hypacrosaurus and other Late Cretaceous dinosaurs.

Kritosaurus was a large, flat-headed duckbilled dinosaur. It had a ridge of bone between the eyes and the snout that gave it a distinguished "Roman nose" appearance.

Lambeosaurus lived at the end of the Late Cretaceous. It was a hollow-crested hadrosaurid that lived at the same time and in the same places as Corythosaurus and Parasaurolophus. Learn more about the Lambeosaurus and other Late Cretaceous dinosaurs.

Leptoceratops, the first known protoceratopsid, was found along the Red Deer River of Alberta, Canada, in 1910. This partial skull and skeleton was named Leptoceratops gracilis.

Since it was named in 1979 by John Horner and Robert Makela, Maiasaura has become one of the most famous dinosaurs. It has provided information about how it cared for its young and the early development of dinosaurs. Learn more about the Maiasaura.

Known from only a single skull and jaw from Montana and three teeth from South Dakota, Nanotyrannus was first thought to be an Albertosaurus. But it was recently redescribed because it was different in many ways from Albertosaurus.

Discovered by the Joint Polish-Mongolian Paleontological Expedition in 1965, the sauropod Opisthocoelicaudia is known from a skeleton with nearly all the bones of the body except the neck and head. Learn more about the Opisthocoelicaudia.

The Ornithomimus has been found mainly in the Late Cretaceous Judith River and Horseshoe Canyon Formations of Alberta, but less-complete specimens have been found in the western United States as well. Learn more about the Ornithomimus.

Orodromeus is a recently discovered dinosaur and one of the most spectacular. Orodromeus (the name means 'mountain runner') was only about 6 1/2 feet long as an adult. Learn more about the Orodromeus and other Late Cretaceous dinosaurs.

The first specimen of Oviraptor was discovered by the American Museum of Natural History expedition to Asia in 1923. It was found in the Gobi Desert of Mongolia.

The largest pachycephalosaur was Pachycephalosaurus. First found in rocks of Late Cretaceous age in Montana, Pachycephalosaurus was named and described by Barnum Brown and Eric Schlaikjer. Learn more about the Pachycephalosaurus.

Pachyrhinosaurus was probably the most unusual and distinctive ceratopsid. It did not have brow or nasal horns; instead it had a thick, bumpy, spongy pad of bone along the upper surface of its flattened face. Learn more about the Pachyrhinosaurus.

Panoplosaurus is known only from two partial skeletons, one of which preserves some of the armor the way it was in life. This skeleton shows that Panoplosaurus was unusual among nodosaurids because it did not have spikes on the sides of its neck.

Parasaurolophus was an interesting-looking dinosaur. While it looked normal from the neck down, it looked almost as if it had a trombone on its head. And in a way, it did.

Not many fossils of Parksosaurus have been found. It is known only from a single skeleton and poorly preserved skull from the southern part of Alberta. Learn about Parksosaurus, Late Cretaceous dinosaurs and dinosaurs of all eras.

Known only from the Late Cretaceous of northwestern New Mexico, Pentaceratops had one large horn on its snout is a pair of large horns above its eyes is and a pair of much smaller false horns in the cheek region. Its name means "five-horned face." The horns were actually bone.