Mammals that lay eggs instead of giving birth to live young like marsupials. Urinary, defecatory, and reproductive systems all open into a single duct, the cloaca.
Female has two lateral vagina, which led to two seperate uteri and Males have two penises. They carry their young in pouches.
a placenta consisting of two parts, almost entirely detached, being united only at the point of attachment of the cord
a placenta consisting of the uteri joined at the cervic often found in large cats
a placenta consisting of 2 uterine horns + uterine body + cervic often found in artiodactlys
all 6 layers present, least intimate, non deciduous often seen in pigs, horses, lemurs, and whales
layers 1-3 are lost, deciduous, seen in insectivores, bats, "higher primates" and most rodents