Interpretation of the fossil record of conodonts hinges on whether conodont elements were retained through the life of the animal or were periodically shed and replaced. Many quantitative analyses of conodont paleoecology and statistical techniques in conodont taxonomy, for example, rely on an assumed correspondence between numbers of elements and numbers of animals, but the possibility that conodonts shed their elements may undermine this assumption. As with many aspects of conodont paleobiology, hypotheses of shedding versus retention of elements have been difficult to test. Here, we describe recurrent patterns of damage resulting from element function in vivo which indicate that internal discontinuities within an element represent periods of use followed by further growth. The cyclical alternation of phases of growth and function provides compelling evidence that elements were retained through the life of the animal.