A Guide to the Dinosaurs of Colorado

The Basics of Taxonomy

Therefore, starting with Linneaus, biologist have over time added additional, larger and higher level group names, called taxons (plural: taxa), from Family up to Kingdom, arranged in a hierarchical order, until a standardized 7-level hierarchy was established, as follows:

To further facilitate grouping similar or closely related groups, these taxa may be further divided with up to three named intermediate-level taxa, as required. For example:

The taxa Superkingdom and Infraspecies are generally not used, leaving a maximum of 26 possible taxonomic categories, although all are rarely required for any given species (or subspecies).

The original purpose of taxonomy was the recognition, categorization, and identification of organisms. Therefore, species were grouped into higher level taxa based primarily by apparent resemblance or by the possession of shared traits. With the widespread acceptance of the theory of evolution, more of an attempt was made to group species in accordance with their evolutionary history. This endeavor is what lead to the creation of the sub-taxon groups, in order that taxonomists could more accurately depict evolutionary relationships between species or other taxa. As our understanding of evolution increased, and our tools for determining evolutionary history and genetic relationships became more sophisticated, the task of ordering species into only 26 or 28 taxons became impossible. That is when cladistics was invented.