The word dinosaur (meaning “fearful lizard”) was first used by English paleontologist and comparative anatomist Richard Owen (1804–1892) to describe a group of large extinct reptiles. Today, they are considered an extremely diverse group of animals of the clade (a type of classification) Dinosauria that first appeared about 230 million years ago, dominated the land (no dinosaurs lived in water or in the air) for about 135 million years, and died out “suddenly” (in terms of geologic time) about sixty-five million years ago.