There are three classes of changes to developmentally accomplish paedo- or peramorphosis: (1) progenesis or hypermorphosis, where maturation with respect to the trait is reached early in the former and continues late in the latter; (2) neoteny or acceleration, where development occurs more slowly in the former and more rapidly in the latter; and (3) pre-displacement or postdisplacement, where development begins later in the former and earlier in the latter.
Source: wiktionary