Heterochrony
Heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape.
Note: distinction between somatic features and that of maturation of the gonads (ontwikkeling van voorplantingsorganen): sometimes it may be beneficial to mature and reproduce rapidly (minimum investment in somatic growth), e.g. aphids, but sometimes it may pay to elaborate somatic features that confer competitive superiority in raising offspring in the face of resource limitation, e.g. birds of prey.
paedomorphosis: evolution of a more 'juvenilized' morphology of the reproductive adult.
Example: axolotls do not undergo metamorphosis as many other salamanders.
Paedomorphosis can be caused by:
neoteny: reducing the growth rate of somatic characters (e.g. the oxalotl), or by
progenesis: cessation of growth at an earlier age (species are small and seem to have had an abbreviated development)
peramorphosis: delayed maturity that often results in reproduction at a larger size and with 'hyper adult' features. (E.g. large size of the human brain).