Implacentalia
noun plural
Im·plac·en·ta·lia
(ˈ)im-ˌplas-ᵊn-ˈtā-lē-ə 
in former classifications
: the monotremes and marsupials regarded as a systematic unit characterized by the absence or rudimentary development of a placenta
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“Implacentalia.” Merriam-Webster.com Medical Dictionary, Merriam-Webster, https://www.merriam-webster.com/medical/Implacentalia. Accessed 3 Nov. 2025.
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