Dental and mandibular measurements on a sample of Gulo gulo of possible Sangamonian to Wisconsinan age from the Old Crow Basin in the Yukon average 2.7% smaller than comparable measurements of the extant form. The difference in the width of P4 is statistically significant. These results do not differ significantly from Harington's previous analysis of a similar sample from Old Crow, and comparable data from the two studies were pooled. Dimensions in the pooled fossil sample average 4.3% smaller; differences in the length and width of both P4 and M1, and the length of the P4–M1, tooth row are significant. Bivariate analysis indicates that P2 and P4 are significantly narrower in the fossil sample. Old Crow wolverines conform to the general trend of increasing size and broadening of certain teeth, especially P4, from the mid-Pleistocene appearance of Gulo in Europe and North America to the end of the Wisconsinan. Referral of the small mid-Pleistocene Gulo to a distinct chronospecies, G. schlosseri, is questioned based on fluctuations in the size of the teeth and the variation associated with other trends in dental morphology in wolverine populations during the Quaternary in Europe and North America.