Bing found the following results
Ordovician - Wikipedia
Ordovician Period | Major Events, Extinction, & Facts | Britannica
Ordovician Period Information and Facts | National Geographic
The Ordovician Period - University of California Museum of …
Ordovician Period summary | Britannica
Ordovician Period | Natural History Museum
Ordovician-Silurian extinction | Overview & Facts | Britannica
Ordovician - New World Encyclopedia
Prehistoric Life During the Ordovician Period - ThoughtCo
The Ordovician - University of California Museum of Paleontology