41. In placental mammals this process of gestation occurs inside the reproductive system of the mother of the embryo. 42. The exceptions to dichromatic vision in placental mammals are monochromats, and both sexes of howler monkeys are trichromats. 43. In extant placental mammals , the maximum dental formula is : Mammal teeth are usually symmetrical, but not always. 44. Further evidence is needed, however, to indicate whether that was important in their diverging from placental mammals , they added. 45. Afrotheria is now recognized as one of the three major groups within the Eutheria ( containing placental mammals ). 46. Marsupial and placental mammals do not lay eggs, but their unborn young do have the complex tissues that identify amniotes. 47. In healthy humans ( and placental mammals the male ejects urine through the penis, and the female through the vulva. 48. Mammals found to possess these genes include monotremes ( platypus ) and marsupials ( opossum ) but not placental mammals . 49. See list of placental mammals and list of monotremes and marsupials for more detailed information on mammal genera and species. 50. This find suggests that placental mammals did coexist with marsupials in Australia in the early Tertiary, although only marsupials persisted.
