In developmental biology

Developmental biology

Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...

, 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 pedomorphosis.
Peramorphosis can also be defined as the delaying of maturity while the development of the adult is extended.

There are several kinds of peramorphism which may appear independently or in combination:

• Acceleration
  Acceleration
  In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
  
  , 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 Protector
  Pak Protector
  Pak Breeders and Pak Protectors are two forms of fictional life in Larry Niven's Known Space universe. The Pak first appeared in "The Adults," which appeared in Galaxy in 1967; this story was expanded into the novel Protector by Larry Niven...
  
  s in Larry Niven
  Larry Niven
  Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...
  
  's Known Space
  Known Space
  Known Space is the fictional setting of some dozen science fiction novels and several collections of short stories written by author Larry Niven. It has also in part been used as a shared universe in the Man-Kzin Wars spin-off anthologies sub-series....
  
  universe.