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