KT Event

K–T extinction, abbreviation of Cretaceous–Tertiary extinction, also called K–Pg extinction or Cretaceous–Paleogene extinction, a global extinction event responsible for eliminating approximately 80 percent of all species of animals at or very close to the boundary between the Cretaceous and Paleogene periods, about 66 million years ago. The K–T extinction was characterized by the elimination of many lines of animals that were important elements of the Mesozoic Era (251.9 million to 66 million years ago), including nearly all of the dinosaurs and many marine invertebrates. The event receives its name from the German word Kreide, meaning “chalk” (which references the chalky sediment of the Cretaceous Period), and the word Tertiary, which was traditionally used to describe the period of time spanning the Paleogene and Neogene periods. The K–T extinction ranks third in severity of the five major extinction episodes that punctuate the span of geologic time.