Sizes [ln (L × W) in millimeters] of lower premolars and molars of North American Dissacus species from the Torrejonian, middle Paleocene, through Wasatchian, early Eocene, strata. The range of variation expected in each sample is 0.40 units on a natural-log (ln) scale (mean ± two standard deviations, where s = 0.10; e.g., Gingerich, 1989, p. 25; Gingerich, 2019). Abbreviations: Cf = Clarkforkian; m = meter level in the Cabin Fork master section; PB = Polecat Bench; Ti = Tiffanian; To = Torrejonian; Wa = Wasatchian.