| 300 | First Egg-Laying Reptiles(300 mya) | The first egg-laying reptiles appeared around 300 million years ago. These reptiles were not dinosaurs, but did share some characteristics with them. |
| 248 | Permian Extinction(248 mya) | At the end of the Permian era, there was a significant mass extinction event, killing off many species on earth, particularly those on land. |
| 248 | Beginning of the Triassic(248 mya) | 248 million years ago, the Triassic began, immediately after the Permian extinction. There were, at the beginning of this era, relatively few surviving species. |
| 228 | First Dinosaurs(228 mya) | The first dinosaurs appeared around this time. These included prosauropods, or early plant-eaters, as well as early two-legged carnivorous dinosaurs. |
| 205 | Beginning of the Jurassic(205 mya) | The Jurassic era began 205 million years ago. The Jurassic is often considered the age of the dinosaurs. |
| 150 | Birds Took Flight(150 mya) | By 105 million years ago, some dinosaurs had evolved into birds, possibly beginning with the feathered archaeopteryx. |
| 145 | Beginning of the Cretaceous(145 mya) | The Cretaceous period began 145 million years ago. Many of the dinosaurs most familiar to us today evolved during this period. |
| 140 | First Apatosaurus, Allosaurus, Stegosaurus(140 mya) | The first apatosaurus, allosaurus and stegosaurus appeared around 140 million years ago. The stegosaurus was armored, while the allosaurus was a two-legged carnivore, much like his later and larger cousin, the tyrannosaurus rex. |
| 70 | First Triceratops, Tyrannosaurus Rex(70 mya) | The triceratops, with massive armor plates around its head and three horns, as well as the massive tyrannosaurus rex appeared around 70 million years ago. These giants had a relatively short reign on earth, as their time was soon to come to an end. |
| 65 | Extinction of Dinosaurs(65 mya) | Sixty-five million years ago, a massive asteroid struck earth causing rapid and severe climate change, fires, and hard to survive atmospheric conditions. This led to the extinction of the dinosaurs, with the exceptions of those that had evolved into birds. |
| 1824 | William Buckland Described Megalosaurus | For many years, dinosaur bones were attributed to giants, dragons or other mythical beings. It was only in 1824 that these creatures were recognized as massive reptiles. Buckland first named and described one of these, the megalosaurus, in 1824. |
| 1841 | Sir Richard Owen Created the Word Dinosaur | With several identified giant extinct "lizards," Sir Richard Owen coined a term for these creatures, calling them by the name we still use today, dinosaur. |
| 1854 | Benjamin Waterhouse Hawkins Produced Life-Size Models | In 1854, Benjamin Waterhouse Hawkins produced the first life-size models of a dinosaur. These were, by modern standards, quite poor reconstructions. |
| 1877 | Bone Wars(1877-1892) | With paleontology in fashion, explorers sought to find more and bigger dinosaur specimens in the American West, leading to a sometimes violent competition and conflict known as the Bone Wars. |
| 1969 | Geographical Expansion of Paleontology(After 1969) | In the second half of the 20th century, and the first part of the 21st, new explorations in different regions have provided a new understanding of dinosaur evolution with key finds in South America, Africa and China. |
