Box 3 in Assessing dinosaur growth patterns: a microscopic revolution

Box 3. Making dinosaur growth curves Longevity estimates are coupled with size data (from direct measures of length or mass estimates from bone circumferences) for dinosaurs to make age-versus-size growth curves. In Figure Ia, femur length was used for the sauropod Janeschia to produce a simple growth curve. This plot was used for determining the age of sexual maturity (hypothesized as occurring when the growth rates initially slowed) and somatic maturity (full adult size as indicated by the asymptote [23]). The curve can also be used to assess linear growth rates at various points in development. (Redrawn and reproduced with permission from [23].) Age-versus-mass growth curves, such as the one shown in Figure Ib for North American tyrannosaurs [12], are generally sigmoidal in shape, except in cases where older adult animals are not represented and the asymptote is absent. Timing to somatic maturity, mass standardized maximal growth rates and other life-history parameters can be assessed and used in both interspecific comparative and evolutionary contexts from this type of curve. (Redrawn and reproduced with permission from [12].)