Figure 1 - Global biodiversity change at family level through the early Palaeozoic era.
From the following article
Asteroid breakup linked to the Great Ordovician Biodiversification Event
Birger Schmitz, David A. T. Harper, Bernhard Peucker-Ehrenbrink, Svend Stouge, Carl Alwmark, Anders Cronholm, Stig M. Bergström, Mario Tassinari & Wang Xiaofeng
Nature Geoscience 1, 49 - 53 (2008) Published online: 16 December 2007
doi:10.1038/ngeo.2007.37
Although this diagram from Sepkoski (1995; ref. 15) gives a good representation of the overall biodiversity trend, the resolution is too crude for correlation with field data. Trem.=Tremadocian (Global) and Tremadoc (British), Ash.=Ashgill, Lland.=Llandovery, We.=Wenlock, Lud.=Ludlow, F.=Floian, Dap.=Dapingian, Sand.=Sandbian, H.=Hirnantian.