Figure 1. A mid-twentieth century phylogenetic tree for the Protozoa sensu lato, with indication of other major eukaryotic lineages as well, proposed essentially before evolutionarily helpful data were available from ultrastructural and molecular biological research studies but compatible with taxonomic schemes of the time (modified from Corliss, (1960), 1998a).

Figure 2. Modern evolutionary/phylogenetic ‘trees’ for the biotic world, with emphasis on the eukaryotes and on the protistan assemblages (including major protozoan groups: note asterisks) therein, based primarily on molecular (rRNA sequencing) data. (a) Modified from Schlegel's (1998) alteration of a figure originally in Leipe and Hausmann 1993); (b) modified from Schlegel's (1998) alteration of a figure originally in Sogin (1991); and (c) modified from a figure in Sogin and Hinkle (1997). Note the clusters of groups; but such arrangements do not (yet) match any particular proposed taxonomic scheme and even seem to differ quite substantially among themselves.