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having no placenta.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
Without a placenta; denoting the monotremes (which lay eggs and have no placenta) and the marsupials (which have a transitory simple yolk-sac placenta).
Farlex Partner Medical Dictionary © Farlex 2012
Having no placenta, as marsupials and monotremes.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.