Dinosaur History

Dinosaur history ended 65 million years ago.

Dinosaurs lived between 220 and 65 million years ago.

Although the age of dinosaurs is the Mesosoic Era, (which is divided into three periods - Triassic, Jurassic and Cretaceous), dinosaurs actually first evolved towards the end of Triassic. Dinosaurs evolved from the ancient archosaurs, so the first dinosaurs were like archosaurs.
Two Allosaurus Predators Plan their Attack on a Young Omeisaurus
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From there they evolved into two groups - saurischia, and (later) ornithischia. The difference between the two were their hip bones - saurischias were "lizard-hipped", and ornithischias were "bird-hipped".

A Nanotyrannus Crushes the Last Flower in a Prehistoric Landscape
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evolved into two groups: Sauropodomorpha and Theropoda.

were carnivorous dinosaurs, they were quick runners and moved on two feet. Their front feet were small, a bit like these of kangaroos. Theropods developed futher to Herrerasaurs, Coelophysosaurs, neocreatosaurs (which later developed to abelisaurs), and Tetanurae - a group that further developed to coelurosaurs, carnosaurs, spinosaurs, allosaurs, Compsognathidae, Therizinosaurs, Troodontidae, Ornithomimosaurs, oviraptorosaurs, alvarezsaurs, deinonychosaurs, and Tyrannosaurs. They were all meat eaters except Therizinosaurs, which returned to eating plants.

Illustration of a Herd of Tanystropheus Reptiles
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Sauropodomorpha were long-necked plant eaters with lizard-like feet. They further evolved into two different groups: Prosauropods (massospondylidae, plateosauridae, melanorosauridae and ancisauridae); and sauropods - the largest animals that have ever excisted. They were massive long-necked elephantine plant-eaters which, due to their weight, walked on four legs. They included cetiosaurs, dicraeosaurs, Euheloptidae, Diplodocidae, Vulcanodontidae, and Macronaria (which later developed into titanosaurs).

A Albertaceratops Wanders a Cretaceous Forest
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Ornithischia, the second large group that dinosaurs evolved to, were bird-hipped plant eaters. They evolved into five groups: Ornithopoda, Fabrosauridae, Heterodontosauridae, Thyreophora and Marginocephalia. Ornithopoda were bird-footed plant eaters that evolved to Hypsilophontidae, and Iguanodontidae which further evolved to hadrosaurs, lambeosaurs, and hadrosaurs (Edmontosaurini, Maiasaurini, Saurolophini, and hadrosaurini). Thyreophora were armoured dinosaurs, which evolved to spectacular stegosaurs (with plated back), and Ankylosauria, which further evolved into Nodosauridae and Ankylosauridae (Polaxanthidae and Ankylosaurinae). Marginocephalia were also armoured, but with horns on their heads instead of spikes or plated on their backs. They evolved into two groups: Patchycephalosaurs (boneheads) and Ceratopsia (hornheads), which further evolved into neoceratopsia, ceratopsidae, centrosaurinae, ceratopsinae and chasmosaurini. That's the main lines in dinosaur history.

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