"kenogenesis" in the noun sense
1. cenogenesis, kenogenesis, caenogenesis, cainogenesis, kainogenesis
introduction during embryonic development of characters or structure not present in the earlier evolutionary history of the strain or species (such as the addition of the placenta in mammalian evolution)
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License