This study comprehensively surveys diploid chromosome numbers across terrestrial mammal families using Wilson and Reeder’s classification. The data are organized around families, subfamilies, tribes, and genera to determine the extent of and identify trends and patterns in diploid number changes. A preliminary survey of nine established baramins revealed approximately 75% with significantly variable diploid numbers. An extensive compilation of chromosome numbers across 113 families that contain more than one species shows similar distribution with 75% variability using a strict definition of stability. There are many factors to examine such as speciose groups, high reproductive rates, and identifying parameters for defining stability. However, karyotype form diversity was found to be prevalent in spite of these considerations. Assuming that the rank of family approximates a baramin and using looser parameters to define constancy in diploid numbers, 62 families exhibit relative karyotype stability, 19 families with more extensive variation might be explained by multiple centric fusions and the remaining 48 families have unusual karyotype deviations.
