Field dinos 2

Tyrannosaurus Rex (left) and Apatosaurus (right) skeletons at the American Museum of Natural History in New York City.

Dinosaurs are an extremely successful group of archosaurian reptiles that first appeared about 240 million years ago, and exist today, in the form of birds. There were many different kinds of dinosaurs. Some were herbivores, some were carnivores, and some were omnivores, like we humans are today.

They are divided into two groups, based on the structure of their hips: the Ornithischians (meaning "Bird-Hipped") and Saurischians (meaning "Lizard-Hipped"). However, do you know what the really big surprise is? Despite what you're probably thinking right now, even though birds are dinosaurs, they are not bird-hipped dinosaurs! Instead, they are actually lizard-hipped dinosaurs.

The similarities in hip structure between ornithischians and modern birds is a classic example of Convergent Evolution, a phenomenon when two or more animals that are not closely related evolve very similar features, in order to adapt to very similar environments. Triceratops and rhinos are another example of Convergent Evolution.