Boundary A B C D E F G H I J Series System Erathem Eonothem Hadaean/Archaean 1 0 0 - 0% - Hadaean/Archaean Eoarchean/Paleoarchean 2 0 0 - 0% - Paleoarcean/Mesoarchean 3 8 0 - 0% - Mesoarchean/Neoarchean 4 0 0 - 0% - Neoarchean/Paleoproterozoic 5 2 0 - 0% - Archaean/Proterozoic Siderian/Rhyacian 6 0 0 - 0% - Rhyacian/Orosirian 7 0 0 - 0% - Orosirian/Statherian 8 37 0 - 0% - Statherian/Calymmian 9 84 7 - 8% - Paleo-/Mesoproterozoic Calymmian/Ectasian 10 82 10 43% 12% 46% Ectasian/Stenian 11 24 0 -100% 0% -100% Stenian/Tonian 12 20 0 - 0% - Meso-/Neoproterozoic Tonian/Cryogenian 13 161 0 - 0% - B Cryogenian/Ediacaran 14 36 0 - 0% - Ediacaran/Cambrian 15 203 1 - 0.5% - Ediacaran/Cambrian Fortunian/Cambrian stage 2 16 134 35 3400% 26% 5202% Cambrian stage 2/Cambrian stage 3 17 0 0 -100% 0% -100% Terreneuvian/series 2 Cambrian stage 3/Cambrian stage 4 18 71 0 - 0% - Cambrian stage 4/Cambrian stage 5 19 0 0 - 0% - series 2/series 3 Cambrian state 5/Drumian 20 34 0 - 0% - Drumian/Guzhangian 21 207 23 - 11% - Guzhangian/Paibian 22 460 0 -100% 0% -100% series 3/Furongian Paibian/Jiangshanian 23 24 0 - 0% - Jiangshanian/Cambrian stage 10 24 0 0 - 0% - Cambrian stage 10/Tremadocian 25 0 0 - 0% - Cambrian/Ordovician Tremadocian/Floian 26 973 31 - 3% - P Floian/Dapingian 27 506 48 55% 235% 9% 198% 728% E Lo/M Ordovician Dapingian/Darriwilian 28 394 104 117% 26% 178% Darriwilian/Sandbian 29 801 50 -52% 6% -76% B M/U Ordovician Sandbian/Katian 30 584 60 20% 114% 10% 65% Katian/Hirnantian 31 1962 107 78% 5% -47% -58% 2 Hirnantian/Rhuddanian 32 486 21 -80% 4% -21% 2 P Ordovician/Silurian Rhuddanian/Aeronian 33 250 57 171% 352% 23% 428% Aeronian/Telychian 34 433 95 67% 22% -4% -42% Telychian/Sheinwoodian 35 560 74 -22% 13% -40% Llandovery/Wenlock Sheinwoodian/Homerian 36 422 88 19% 21% 58% 87% WISE and RICHARDSON Biostratigraphic continuity and earth history 2023 ICC 613 Table 1. The Boundary column lists the global stratigraphic boundaries utilized by the PBDB, arranged from the oldest at the top to the youngest at the bottom, identified with the names of the underlying and overlying stratigraphic units, separated by a forward slash. Note that the numbered ‘Cambrian stage’ units have not yet been given formal stage names (thus they are denoted by a lower case ‘stage’ and a number 1 through 10). Column A numbers the stratigraphic boundaries from the oldest to the youngest for easy reference in the text. Column B is the total number of different species reported in the PBDB in the global stratigraphic unit below the boundary. Column C is the Number of Local Stage-Straddling Species (NLSSS) for that boundary (the number of different species from PBDB data that are found in the global stratigraphic unit below and above the boundary at locations within 2 degrees longitude and latitude of one another). Column D is the percent change in NLSSS from the previous boundary. Column E is the total percent change in NLSSS in those cases where the NLSSS has increased or decreased over multiple successive boundaries. Column F is the %NLSSS (the percent of species below the boundary that straddle the boundary—i.e., column C divided by column B). Column G is the percentage change in %NLSSS from the previous boundary. Column H is the total percent change in %NLSSS in those cases where the %NLSSS has increased or decreased over multiple successive boundaries. Column I is the rank of a mass extinction’s intensity that occurred at or near the boundary. This rank is based on the average of several genus-level extinction studies, beginning with the most substantial extinction as a 1. Column J is North American megasequence data (B denoting the approximate beginning of the megasequence, P denoting the approximate peak, and E denoting the approximate termination of the megasequence). The last column contains the higher global stratigraphic units that bound at the same level, with the unit below the boundary mentioned first and the unit above the boundary mentioned second.
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