A form of heterochrony in which, during the course of evolution, the rate of development is unchanged but the total development time is extended, permitting the addition of new stages to the end of the ancestral development sequence. The morphological outcome is an example of peramorphosis. Hence the development (ontogeny) of such organisms conforms to the theory of recapitulation of their phylogeny.
From: hypermorphosis in A Dictionary of Biology »
Subjects: Science and technology — Life Sciences