Taxonomy is a scientific system that classifies things, especially organisms, into related groups. Complex and precise, classification narrows a thing from its place in a broad category down through ever-more-exacting descriptions. It separates the characteristics of, say, squirrels from opossums and daisies from turnips.
Taxonomy isn’t static, it routinely undergoes challenges and upheavals as new technological capabilities, such as DNA analysis, keep taxonomists reclassifying and rearranging species. Not only that, but new species are discovered all the time, adding to a system that’s already enormous in size — currently about 1.8 million species.
Shown at the top of this page is the basic hierarchical classification of the Red Fox. What isn’t shown are the many intermediate levels that lead to a description that fits a Red Fox, and only a Red Fox. A more complete classification is shown below.
Notice the hierarchy begins with the broadest category, Domain, which includes virtually every living thing in the world. At each subsequent level, which is technically called a taxon (plural: taxa), the description is more specific. The final two taxa, genus and species, become this fox’s scientific name. So, only the Red Fox, Vulpes vulpes, meets every single description from top to bottom. The Kit Fox, Vulpes macrotis, the Arctic Fox, Vulpes lagopus, and others do not exactly fit the Vulpes vulpes description. And vice versa.
Domain: Eukaryote (cells with membrane-bound nucleus – humans, plants, etc.)
Kingdom: Animalia (animals: multi-cellular, must eat for energy)
Eumetazoa: metazoans (having germ layers, neurons, embryonic gestation)
Bilateria: bilaterally symmetrical animals
Deuterostomia: deuterostomes (distinguishing sequence of embryonic development)
Phylum: Chordata (notochord, dorsal hollow nerve cord, pharyngeal slits)
Craniata: craniates (vertebral column and bony vertebrae)
Subphylum: Vertebrata (vertebrates: vertebrae during embryonic period)
Superclass: Gnathostomata (jawed vertebrates)
Euteleostomi: bony vertebrates
Class: Sarcopterygii (lobe-finned fishes and terrestrial vertebrates)
Tetrapoda: tetrapods (tetrapods: four legs)
Amniota: amniotes: embryo develops within a protective membrane)
Synapsida: synapsids: bony arch behind each eye)
Class: Mammalia (mammary glands, hair, diaphragm)
Subclass: Theria (Therian mammals: give birth to live young)
Infraclass: Eutheria (placental mammals)
Order: Carnivora (carnivores: eat meat)
Suborder: Caniformia (caniform carnivores: long jaw, nonretractile claws)
Family: Canidae (coyotes, dogs, foxes, jackals, wolves)
Genus: Vulpes (smaller size, flatter skull, pelt markings and colors)
Species: V. vulpes (Red Fox: pelt color, markings)
Scientific name: Vulpes vulpes (Linnaeus, 1758)
Scientific classification was first designed by Carl Linnaeus (1707-1778), a Swedish botanist and physician who loved nature. Called the Father of Taxonomy, during his lifetime he classified several thousand species.
Scientists use “binominal nomenclature” to name life on our planet. This simply means they use two words for a name — the genus and species. Think of the genus as equivalent to a human’s last name, with the species being the first name. Using the example above, there are many foxes with the “last name” of Vulpes, but only one with the “first name” of vulpes. An exception to the two-name rule occurs when referring to a subspecies. Then three names are allowed, such as Homo sapiens sapiens.
You’ve no doubt noticed that the scientific names are always in Latin, hard to decipher and hard to pronounce, unless you speak Latin (even then, scientists differ on pronunciation). This custom serves a purpose, however, as it avoids confusion between speakers of different languages. For example, in Spanish a “Red Fox” is Zorro rojo; in German it’s roter Fuchs; and in Greek it’s κόκκινη αλεπού. But, every scientist in the world knows which animal this is through its Latin name, Vulpes vulpes.
There are formal international agreements setting forth tons of rules for naming species. One of the rules concerns the “discoverer.” You may have noticed above that Linnaeus’ name follows the scientific name of the Red Fox. This tells us he’s the first person to describe this species. Sometimes it’s found that two individuals have given different names to the same species. In that case, only the first describer is recognized.
Just for fun, here’s another classification, this time using humans, because we can easily relate to the physical descriptions that separate us from other animals at each level.
The rules for nomenclature set out through the International Code of Zoological Nomenclature and others are numerous and involve more than we will cover here. But to give you a final example of how exacting classification can be, here’s the taxonomy¹ for the Striped Skunk, complete with all appropriate citations.