| Koalas are unusual among marsupials in that they briefly form a placenta during the gestation of their embryos. |
| If a third ovule is present, it is obliquely directed and its placenta is lateral. |
| The embryo forms an allantoic placenta, as is true of at least some peramelids and koalas but not other marsupials. |
| Do you think the platypus has a placenta, as a human mother would have when she is pregnant? |
| A placenta or afterbirth is attached to the wall of the uterus and is the source of food and oxygen for the puppy inside the matron. |
| He pointed out that whales share a number of traits with land mammals, such as milk and a placenta. |
