They are indeed extinct, but spread over that time span. The "mass" in "mass extinction" come from the fact that a much greater # than usual are going extinct a

They are indeed extinct, but spread over that time span. The "mass" in "mass extinction" come from the fact that a much greater # than usual are going extinct at the same time. Which is the case today. You may eat one burger a day for a long time. Which adds to a lot of burgers. In fact, 99.99% of all burgers you ate. But if you ate 100 burgers in one single day, I'd say something is wrong with you. Similarly, in a mass extinction, we are killing a great number of species, in a short amount of time, by completely altering the habitat/ecology of entire regions of Earth. Darwinian extinction on the other hand is driven by being out-competed by other species exploring the problem space, and long-term geological change.