Taxonomic names: Format them right!

Flower for taxonomy postTaxonomy (the study of classification), provides scientific writers with a system for organizing and naming living things. Each organism belongs to a series of ranked taxonomic categories, such as class, order, family, etc. (see overview here by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye).

The basic systematic ranks or taxa (singular is “taxon”), in descending order, are:

  1. Domain
  2. Kingdom
  3. Phylum (animals and bacteria) or Division (plants and fungi)
  4. Class
  5. Order
  6. Family
  7. Genus
  8. Species

A number of formatting rules govern the way taxonomic descriptors are written:

  1. Names of taxa at the level of genus and below should be written in italics. This includes genus, species, subspecies, variety, and forma.
  • Poa species are widespread in North America.
  • Most tuberculosis is caused by Mycobacterium tuberculosis.
  • The sulfate-reducing bacteria Desulfovibrio desulfuricans aesturii is found in estuarine sediments.


  1. Names of taxa at the level of family or above should be in roman type (there are exceptions for bacteria and viruses).
  • Most Salmonellae encountered in EID will be serotypes.
  • The plant kingdom includes Bryophyta (bryophytes) and Tracheophyta (tracheophytes).
  • The family Malvaceae includes both temperate and tropical plant species.
  • Sharks belong to the class Chondrichthyes.
  • Prokaryotes are classified into the domains Archaea and Bacteria.


  1. Use an initial capital letter for the names of all taxa down through genus.
  • They sampled Musca domestica (Diptera: Muscidae).
  • Humans, Homo sapiens, belong to phylum Chordata, class Mammalia, and family Hominidae.
  • The complete genome of Shigella boydii (Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacteriales; Enterobacteriaceae; Shigella) is available in databases.


  1. When the term for the taxon precedes the name in text, write the term in lowercase.
  • the kingdom Plantae
  • the phylum Protozoa
  • the family Terebratulidae
  • the genus Salmonella


  1. The term “species” may be abbreviated as sp. if singular and as spp. if plural. Other abbreviations include subsp. for subspecies, var. for variety, and pv. for pathovar. These abbreviations are not italicized.
  • Bacillus thuringiensis subspisraelensis
  • Eucomis autumnalis subspautumnalis
  • Xanthomonas arboricola pv. fragariae
  • Helianthus annuus var. annuus
  • The nesting of crows and ravens (Corvus spp.) was monitored.


  1. Names of genera do not have plural forms.
  • Corvus, NOT Corvuses or Corvi
  • Carya, NOT Caryas


  1. In addition, the binomial name is always singular, unless followed by “spp.” or other term indicating the plural.
  • Escherichia coli was cultured…
  • Escherichia coli strains were cultured…
  • Poa pratensis was sampled…
  • Poa were sampled…


  1. If two or more species in the same genus are presented, the genus does not need to be spelled out after the first use.
  • The following Pinaceae species were sampled: Pinus strobus, taeda, and P. rigida.


Correct formatting is key when describing taxonomy!


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