242 itj figure 2.1. Geological time scale for the Mesozoic. Source: modified after Palmer and Geissman (1999).

Where possible, we use European marine ages (figure 2.1), or subdivisions thereof; absolute ages follow the geologic time scale of Palmer and Geissman (1999). However, the chronostratigraphic framework is poor for many occurrences; in some cases the epoch is not well established and in a few even the period is questionable. In North America, a sequence of land-mammal "ages" has achieved wide usage for faunas of Campanian and Maastrichtian age, despite some problems with definition (Russell, 1975; see especially reviews by Lillegraven and McKenna, 1986; and Cifelli et al., 2004). Land-vertebrate or land-mammal "ages" have been proposed for earlier assemblages in North America (L. S. Russell, 1964,1975; Lucas, 1993) and for Asia (Jerzykiewicz and Russell, 1991; Lucas, 1996; Lucas and Estep, 1998) and South America (Bonaparte et al., 1987). These "ages" are not widely used, and as they are of limited utility in the current context, we do not employ them, although we refer to them as appropriate. Transliteration of stratigraphic and place names for Russia, Middle Asia, and Mongolia follows Benton (2000a).

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