Lyell's Proposal of the Term "Pleistocene"
AbstractIn order to simplify his terminology of Tertiary subdivisions, and probably at the urging of his friend, Charles Darwin, Charles Lyell introduced the Pleistocene "period" (Wilson, 1972, p. 484-485). The term was substituted for "Newer Pliocene" as the name of the most recent of the Tertiary divisions, based on the ratio of extant to extinct species of fossil mollusks. According to Lyell's original criteria, the presence of ninety percent or more extant species from any formation anywhere in the world indicated deposition during the Newer Pliocene (Lyell, 1833, p. 58-59). (Lyell's concept of percentages recently has undergone a very interesting revival at the hands of evolutionary paleobiologists; see Stanley, 1979, p. 113-118.). Because attributes of assemblages of fossil mollusks were the first keys to the identification of latest Tertiary formations, we reproduce in Figure 1 Lyell's illustration of the species regarded as typical Pliocene forms.