Neoteny, Paedomorphosis, and Paedogenesis

These definitions are derived primarily from: Gould, S. J. 1977. Ontogeny and Phylogeny. Similar definitions can also be found: Hildebrand, M. 1982. Analysis of Vertebrate Structure and Romer, A. S., and T. S. Parsons. 1986. The Vertebrate Body.

NEOTENY: Paedomorphosis (retention of formerly juvenile characters by descendents) produced by retardation of somatic development.

PAEDOMORPHOSIS: The retention of ancestral juvenile characters by ontogenetic stages of descendents.

PAEDOGENESIS: ...2) De Beer's term for paedomorphosis (retention of formerly juvenile characters by adult descendents) produced by precocious sexual maturation of an organism still in a morphologically juvenile stage. Gould prefers the term PROGENESIS for this phenomenon.

One way to classify these terms might be as follows:

I) Paedomorphosis = retention of juvenile characters by adults.

A) Neoteny = retention of juvenile characters by adults. 

B) Paedogenesis (progenesis) = reproduction by a juvenile.

Note: Historically, these terms have had other definitions