 Maddison (1997) represents a more recent launching point for a new appreciation of the role that the internal structure of lineages can play in phylogenetic inference. Briefly, the continued advancement of molecular and computational techniques provided the opportunity to produce ever-finely resolved phylogenies of the systems of interest. What quickly became apparent was a confirmation of what is only implicit in Hennig (1966): that the hierarchical structure of taxa may result in discordant phylogenies at different levels (or even within levels) of the biological hierarchy. As an example, Maddison describes how the phylogenies of individual genes or nucleotides may display different phylogenetic topographies from the organisms or populations in which we sampled those genes. This is not a result of error or homoplasy, but of genuine phylogenetic discordance between gene level lineages and the higher-level lineages in which they reside.