Four distinct stages have been identified in the ontogeny of Diictodon feliceps based on variations in cortical thickness, organization of primary osteons, porosity, incidence of growth marks, and extent of endosteal reconstruction. In general, the cortex comprises fibrolamellar bone tissue suggesting rapid bone deposition and growth. In the initial two stages of growth, when up to 70% of adult size is attained, no growth marks interrupt the fibrolamellar tissue, indicating a sustained, fast growth. Growth marks appear late in ontogeny and indicate periods of slow or complete cessation of growth after which, fast growth resumed. Although growth was interrupted and much slower in the later stages, D. feliceps probably had an indeterminate growth strategy. Variations in cortical thickness, porosity, organization of primary osteons, and incidence of annuli and LAGs are observed between elements of the same individual, suggesting variable inter-elemental growth. The propodials had faster appositional growth than did the epipodials, with the humerus having grown much faster than the femur in the same individual. The high cortical thickness (RBT) and correspondingly low k values suggest that the limbs were selected for impact loading. The relatively high RBT and low k value of the humerus compared to other limb bones indicates that the forelimbs were more modified for postural support and digging.