61:0.1 The era of [[mammals]] extends from the times of the [[origin]] of [http://en.wikipedia.org/wiki/Placenta placental] mammals to the end of the [http://en.wikipedia.org/wiki/Ice_Age ice age], covering a little less than fifty million years. | 61:0.1 The era of [[mammals]] extends from the times of the [[origin]] of [http://en.wikipedia.org/wiki/Placenta placental] mammals to the end of the [http://en.wikipedia.org/wiki/Ice_Age ice age], covering a little less than fifty million years. |