ABSTRACT
Animals represent just one of an estimated 70+ lineages of eukaryotes (Patterson 1999), and the bulk of the remaining lineages are microbial. During the past decade, perspectives of the organization of eukaryotic diversity have undergone a major shift to a system that recognizes fi ve or six high-level groupings (Adl et al. 2005, Tekle et al. 2009). While deep nodes on the eukaryotic tree of life remain elusive (reviewed in Parfrey et al. 2006), the position of animals emerging from within microbial lineages has been robustly resolved by several lines of evidence (King 2004). Animals are placed within the supergroup Opisthokonta, along with fungi and numerous microbial relatives (Adl et al. 2005, Steenkamp et al. 2006).
