noun
or coe·no·genesis also cae·no·genesis |sēnə, |senə+
Etymology: German zänogenesis, from zän- cen- (II) + Latin genesis birth — more at genesis
: introduction during development of adaptive characters or structures that are absent from the earlier phylogeny of a strain (as addition of the placenta to the common vertebrate pattern in mammalian evolution) — opposed to palingenesis