The K/T extinction is probably the most famous but it wasn’t the largest mass extinction event in Earth’s history. In terms of the number of species that disappeared, that distinction belongs to the Permian/Triassic extinction event. That happened right here at about 250 million years ago. This extinction event is more mysterious than the K/T and it is a little bit less well-preserved because it is so much older. Unlike the K/T, impact is one hypothesis but it is not the leading one. However, it is the one that we’re going to study in this lesson.