In Table 26.1, formally defined families and genera assessed to be of familial status are listed under a consensus classification to order, class, and phylum. Informal taxa are used for many problematica, and this classification may change considerably with new discoveries and insights into phylogenetic relationships. Problematical taxa followed in parentheses by an asterisk were treated as equivalent in rank to orders and classes in the analyses of diversity patterns in Section 11.4.

Stratigraphic ranges listed in Table 26.1 represent “best guesses,” especially for the Lower Cambrian, and may change as global correlation becomes more accurate. The units employed represent an attempt to standardize stratigraphy to the Siberian sequence for the Lower Cambrian and to the North American cratonic sequence for the Upper Cambrian. Abbreviations for stratigraphic units are as follows: “V” = Vendian; “Cm” = Cambrian; “Edia” = Ediacaran (upper Vendian); “N-Da” = Nemakit-Daldyn (uppermost Vendian); “Tomm” = Tommotian; “Atda” = Atdabanian; “Boto” = Botomian; “1Mid” = lower Middle Cambrian (as defined in Sepkoski 1979); “mMid” = middle Middle Cambrian; “uMid” = upper Middle Cambrian; “Dres” = Dresbachian; “Fran” = Franconian; “Trep” = Trempealeauan; “1” = lower; “u” = upper. Other stratigraphic abbreviations are as defined in Sepkoski (1982).

Table 26.2 summarizes the time scale used in Section 11.4 in plotting diversity patterns for Vendian-Cambrian metazoans and metaphytes.