Notes: 1  In 1997, MLB retired Jackie Robinson's number 42 meaning no other player in MLB could ever wear it. However, it was grandfathered to anyone who was currently wearing the number. 2  Mariano Rivera is the only Yankee to appear as an active player while wearing his retired number.
The Ordovician Period. The Ordovician Period lasted almost 45 million years, beginning 488.3 million years ago and ending 443.7 million years ago.* During this period, the area north of the tropics was almost entirely ocean, and most of the world's land was collected into the southern supercontinent Gondwana.
During the Ordovician, most of the world's land  southern Europe, Africa, South America, Antarctica, and Australia  was collected together in the super-continent Gondwana. Throughout the Ordovician, Gondwana moved towards the South Pole where it finally came to rest by the end of the period.rom the Lower to Middle Ordovician, the Earth experienced a milder climate  the weather was warm and the atmosphere contained a lot of moisture. However, when Gondwana finally settled on the South Pole during the Upper Ordovician, massive glaciers formed, causing shallow seas to drain and sea levels to drop.