"placental" in the noun sense
1. placental, placental mammal, eutherian, eutherian mammal
mammals having a placenta all mammals except monotremes and marsupials
"placental" in the adjective sense
1. placental
pertaining to or having or occurring by means of a placenta
"all mammals except monotremes and marsupials are placental mammals"
Source: WordNet® (An amazing lexical database of English)
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