Paedomorphosis

Paedomorphosis has occurred when reproduction is seen in what was ancestrally a juvenile morphological stage. This can be the result of neoteny or progenesis.

Two important evolutionary effects of paedomorphism:

• It may stop recapitulation that occurs during the development of the organism.

• It may be important in the origin of higher taxa. The first component of the argument is empirical. For many large groups of animals, the adults appear to resemble an early developmental stage of a possible ancestor.

This Mexican axolotl opposite is a famous example of paedomorphosis, retaining in adulthood the feathery external gills which are normally lost in the development of amphibian organisms.