Abstract: The late Professor Minchen Chow started his career in vertebrate paleontology with a team of scholars working to clarify the biostratigraphy and paleogeography of Paleocene–Eocene change in mammalian faunas. This is the time of first appearance of artiodactyls, perissodactyls, and primates (APP taxa) in the fossil record. Recognition of the Paleocene as an epoch separate from the Eocene started to be accepted in 1911 following discovery of a new Clarkforkian latest–Paleocene mammalian fauna at Polecat Bench in western North America. Later the Paleocene–Eocene boundary was shown to include an interval with dwarfed mammalian lineages. A Paleocene–Eocene carbon isotope excursion (CIE) was discovered coincident with both mammalian dwarfing and the first appearance of APP taxa. This enabled global generalization of the CIE, which is linked in turn to the Paleocene–Eocene thermal maximum (PETM). The PETM was a global greenhouse warming event with transient effects on the earth’s climate and biota, but also profound lasting effects on the biota. Much of what we know about mammals in relation to the CIE and PETM we have learned through high-resolution study of the exceptional stratigraphic record flanking Polecat Bench, where Professor Chow worked early in his career and where his ashes now lie.