What did Georges Cuvier discover?

Georges Cuvier is best known for establishing extinction as a fact rather than a theory. He is also famous for originating the phyla as a classification system for plant and animal organisms.

Prior to Cuvier's work on extinction, scientists disagreed on whether fossils are the remains of still extant organisms or are from species types that no longer exist. Cuvier catalogued the divergent features of different types of elephants to show the variation between the Asian and African members of the species. He then demonstrated that both elephant species differed from discovered fossils to determine that the woolly mammoth had once existed as a separate and distinct organism.