11. Although " Maelestes " was a eutherian, it was not a placental mammal . 12. Male placental mammals have nonfunctional nipples, so do male marsupials have them, as well? 13. Unlike placental mammals , male marsupials have a scrotum that is anterior to the penis. 14. The milk contains a higher amount of iron than the milk of placental mammals . 15. Placental mammals evolved a discrete motor cortex about 100 mya.16. In marsupial and placental mammals , copulation occurs through the vagina. 17. Differences exist between the cleavage in placental mammals and the cleavage in other animals. 18. Placental mammals were also found in North America and South America at this time.19. Modern monotremes have a low body temperature compared to marsupials and placental mammals , around. 20. There marsupials evolved to fill the gaps left by the absence of placental mammals .
