Lacking a placenta; describing mammals that do not develop a placenta during pregnancy.
From 'a-' (without, not) plus 'placental' (from Latin 'placenta,' the afterbirth). Coined in the 19th century for mammalian classification based on reproductive anatomy.
Aplacental mammals include marsupials and monotremes—animals that evolved completely different pregnancy strategies, proving evolution found multiple solutions to one problem!
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