IV. Dinosaur Groups: The Basics

Of course, Dinosauria is itself diverse. It contains several smaller groups, each marked by the evolution of some new set of features. Each group retains the original ancestral features of dinosaurs, but has added something unique.

This most basic division of dinosaurs is into the two great groups: Saurischia and Ornithischia. Therefore, all dinosaurs are either saurischians or ornithischians. The two groups first appeared at the start of the Late Triassic Period, and both survived until the very end of the Late Cretaceous. They are known from all continents—nearly from pole to pole—and a broad range of environments.

To Learn more about the divisions of Dinosaurs into different groups, please visit our Tree of Life Interactive