31. Other than bats and some two dozen indigenous rodent genera, there are no pre-human indigenous placental mammals . 32. In contrast, male placental mammals , including chromosomally stable male cats, have one X and one Y chromosome. 33. Dating to the Eocene epoch over 50 placental mammals ) also possessed an independently evolved toothcomb. 34. At Murgon evidence of a placental mammal , a Condylarth ( " Tingamarra porterorum ) ", was discovered. 35. The indisputable remains of Australian placental mammals started from the Miocene, when Australia moved closer to Indonesia. 36. Calico cats are almost always female because the placental mammals & mdash; normally have two X chromosomes. 37. There are modern genetic studies attempting to figure out the proper cladistics and taxonomy of placental mammals . 38. The platypus has an average placental mammals . 39. Unlike the random X-inactivation in placental mammals , inactivation in marsupials applies exclusively to the paternally derived X chromosome. 40. SRY is a sex-determining gene on the Y chromosome in the therians ( placental mammals and marsupials ).
