This document discusses the phylogeny and taxonomy of protozoans. It presents a cladogram showing the evolutionary relationships between protozoan phyla and other eukaryotes based on 18S ribosomal RNA sequences. The cladogram suggests that protozoan evolution occurred in five major radiations, with Mastigophora and Microspora representing early diverging lineages. The protozoa are classified into four supergroups: Excavata, Amoebozoa, Chromalveolata, and Rhizaria. Within Chromalveolata are the Alveolata, which include dinoflagellates, Apicomplexa, and Ciliophora. Precise evolutionary relationships