pedomorphism

n.
Retention of juvenile characteristics in the adult, occurring in mammals.

pedomorphic ped'o·mor'phic (-fĭk) adj.

or pe·do·mor·phism (pē'də-môr'fĭz'əm)
n.

1. Retention of juvenile characteristics in the adult, occurring in mammals.
2. Description of adult behavior in terms appropriate to child behavior.

pae'do·mor'phic (-fĭk) adj.

retention in the adult of infantile or juvenile characters