The phylum is the second highest ranking of animals in standard scientific taxonomy, and is equivalent to 'Division" for Plants and Bacteria. The original Linnaean taxonomy did not define nor have phyla (plural), and the term was ntroduced by Ernst Haeckel. A Phylum is the taxonomic category between Kingdom and Class, a major ranking of organisms, defined according to the most basic body-parts shared by that group. e.g. Chordata (animals with a notochord - vertebrates and others), Arthropoda (animals with a jointed exoskeleton) Mollusca (animals with a rasping radula and shell-secreting mantle), Angiospermae (flowering plants), and so on. Some traditional Phyla like the Protozoa are no longer valid (polyphyletic). According to Bengstrom (1986), a "typical" phylum is a group of organisms of uncertain (or problematic) taxonomic affinities.