placental has 3 distinct synonyms spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is aplacental.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
mammals having a placenta; all mammals except monotremes and marsupials
Synonyms, antonyms and the broader and narrower relations for placental come from Princeton University’s WordNet. Full sources and licences.
pertaining to or having or occurring by means of a placenta
“all mammals except monotremes and marsupials are placental mammals”