The Ordovician Extinction: Life & Causes
The Ordovician period is placed between 488.3±1.7 to 443.7±1.5 million years ago.1 It is preceded by the Cambrian period and is followed by the Silurian Period as seen in Figure 1.1 Initially, only these two periods existed, until 1979 when Charles Lapworth defined the Ordovician period as a period of its own based on fossil…