Core eudicots include the bulk of extant angiosperm species diversity (Magallón et al., 1999) and can be divided into two large clades (rosids, asterids) together with a small number of lineages of uncertain phylogenetic position (Figure 13.1). In this chapter we deal with those lineages of core eudicots that fall outside the species-rich rosids and asterids, but that potentially occupy an important position in the early evolution of the group.
Classification of core eudicots
A four-gene phylogenetic analysis places Gunnerales (Gunneraceae and Myrothamnaceae) as the sister group to all other core eudicots (Soltis et al., 2003). In the APGII classification (2003) the precise position of such lineages as Berberidopsidales, Saxifragales, Santalales and Caryophyllales–Dilleniaceae was not yet securely determined, but in the latest APG classification (APGIII, 2009) the positions of some of those taxa have been clarified. Berberidopsidales, Santalales and Caryophyllales are resolved as a grade of successive sister lineages to the asterid clade, while the Saxifragales are placed as sister to the rosid clade. In this chapter we describe the fossil record of these lineages of core eudicots that appear to have diverged before the diversification of both rosids and asterids. Some of these lineages, such as the Saxifragales, have a well-documented fossil history extending back to the Late Cretaceous.