Peramorphosis

In developmental biology, peramorphosis is a phylogenetic change in which individuals of a species mature past adulthood and take on hitherto unseen traits. It is the reverse of paedomorphosis. Peramorphosis can also be defined as the delaying of maturity while the development of the adult is extended.

There are several kinds of peramorphism, different dimensions of heterochrony, which may appear independently or in combination:

Acceleration, in which the rate of development is increased (compared to the ancestral condition).
Hypermorphosis, in which offset of development is delayed (compared to the ancestral condition).
Predisplacement, in which onset of development occurs earlier (compared to the ancestral condition).

Peramorphosis in fiction

The Pak Protectors in Larry Niven's Known Space universe.

References

Gould, Stephen Jay (1985). Ontogeny and Phylogeny. Cambridge: Belknap Press. ISBN 0-674-63941-3.

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