BY EVERETT C. OLSON¹

GEORGE GAYLORD SIMPSON'S passing in 1984 brought an era in vertebrate paleontology to an end. Along with Edward Drinker Cope, Henry Fairfield Osborn, and Alfred Sherwood Romer, Simpson ranks among the great paleontologists of our time. The intellects of several generations of students were shaped by either following or rejecting his elegant analyses and interpretations of evolution and the history of life.

Although the ''Simpson Era" had its roots in the 1920s and 1930s, it seemed to emerge fully formed and without precedent with the publication of Tempo and Mode in Evolution (delayed until 1944 by World War II), following belatedly on the heels of Quantitative Zoology (1939), which Simpson had written with Anne Roe. Both books left researchers in a variety of fields pondering and often revising, conceptual bases