This paper presents the first analytical examination of the evidence of growth and aging in pycnodonts. Preliminarily, the author discusses the difficulties of evaluating auxological phenomena in animals that do not have current descendants and in which the anatomical traits typical of juveniles persist in adults (neoteny), as an evolutionary strategy. The author collected biometric data on juvenile and corresponding adult subjects of only 15 pycnodont species. Despite this scarcity of species, the author demonstrates that there does not seem to exist a single pattern of somatic growth. However, at least two characters (one skeletal and one dental) seem common to all the examined species: (i) the relative dimensions of the orbit decrease in a constant, sometimes conspicuous manner with respect to the total body dimensions, and (ii) the width of the interdental diastemas is noticeably reduced during growth. At least two phenomena seem to be present also in aging: (i) bone hypotrophy (detectable only through radiological means) and (ii) the depletion of ameloblastic activity leading to the cessation of polyphyodontia. However, the inability to replace worn teeth may have played a role in causing natural death in aged pycnodonts by interfering with their ability to feed themselves.