| implacental | <zoology> Without a placenta, as marsupials and monotremes. A mammal having no placenta. Source: Websters Dictionary (01 Mar 1998) |
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| implacentalia | <zoology> A primary division of the Mammalia, including the monotremes and marsupials, in which no placenta is formed. Origin: NL. See In- not, and Placental. Source: Websters Dictionary (01 Mar 1998) |