Figure 3 - Total diversity of brachiopod species (number of species) through part of the Lower and Middle Ordovician in Baltoscandia.

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


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The results are based on bed-by-bed collections at eight localities22. Note the dramatic increase in biodiversity (black line) and high extinction (blue line) and origination (red line) levels following the regional Volkhov–Kunda boundary, that is, the same level where extraterrestrial chromite appears and Os isotopes change in Fig. 2. B. triang.-navis=Baltoniodustriangulatus-navis. The dashed lines show the boundaries between the regional states.