Recommendation 6 (1) of the ICNP (2008 Revision) states the following: "Avoid names or epithets that are very long or difficult to pronounce". In spite of Recommendation 6 there are some long monomials and epithets. The longest and shortest names validly published under the ICNP are listed below, assorted by their taxonomic category. Epithets of species and subspecies are treated separately. In the case of species names the count of characters includes the space; in the case of subspecies names the count of characters includes the spaces and the subspecies indication. Other things being equal, taxonomists are advised to propose names and epithets whose length is as close as possible to the modes (the most frequent values) of the lengths listed below for each category.
See also the LPSN introductory page on forming names.
Longest: Thermodesulfovibrionia — Thermosediminibacteria (22 characters)
Shortest: Bacilli (7 characters)
Average: 13.74 characters
Median: 13.00 characters
Mode: 13 characters (lower), 13 characters (upper)
Longest: Gracilicutes (12 characters)
Shortest: Firmacutes — Firmicutes corrig. (10 characters)
Average: 10.67 characters
Median: 10.00 characters
Mode: 10 characters (lower), 10 characters (upper)
Longest: Bacteria (8 characters)
Shortest: Archaea (7 characters)
Average: 7.50 characters
Median: 7.50 characters
Mode: 7 characters (lower), 8 characters (upper)
Longest: Desulfonatronovibrionaceae (26 characters)
Shortest: Orbaceae (8 characters)
Average: 16.38 characters
Median: 16.00 characters
Mode: 17 characters (lower), 17 characters (upper)
Longest: Paratractidigestivibacter — Sphingosinithalassobacter (25 characters)
Shortest: Baia — Puia — Sala (4 characters)
Average: 12.69 characters
Median: 13.00 characters
Mode: 13 characters (lower), 13 characters (upper)
Longest: Methanobacteriati (17 characters)
Shortest: Bacillati (9 characters)
Average: 13.14 characters
Median: 14.00 characters
Mode: 14 characters (lower), 14 characters (upper)
Longest: Caldicellulosiruptorales — Thermodesulfobacteriales — Thermodesulfovibrionales — Thermosediminibacterales (24 characters)
Shortest: Orbales (7 characters)
Average: 15.27 characters
Median: 15.00 characters
Mode: 15 characters (lower), 15 characters (upper)
Longest: Thermodesulfobacteriota (23 characters)
Shortest: Bacillota (9 characters)
Average: 14.32 characters
Median: 14.00 characters
Mode: 16 characters (lower), 16 characters (upper)
Longest: Myxococcus llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogochensis (74 characters)
Shortest: Sala cibi (9 characters)
Average: 22.88 characters
Median: 23.00 characters
Mode: 23 characters (lower), 23 characters (upper)
Longest: Myxococcus llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogochensis (63 characters)
Shortest: Cellulomonas uda — Erythrobacter ani — Lactobacillus uli — Olsenella uli — Pseudoxanthomonas gei — Rhizobium gei — Sphingomonas gei (3 characters)
Average: 9.68 characters
Median: 9.00 characters
Mode: 9 characters (lower), 9 characters (upper)
Longest: Anoxyphotobacteriae (19 characters)
Shortest: Rubrobacteridae (15 characters)
Average: 16.57 characters
Median: 16.00 characters
Mode: 16 characters (lower), 16 characters (upper)
Longest: Gluconoacetobacter (18 characters)
Shortest: Acetobacter (11 characters)
Average: 14.50 characters
Median: 14.50 characters
Mode: 11 characters (lower), 18 characters (upper)
Longest: Propionibacteriineae corrig. — Streptosporangiineae corrig. (20 characters)
Shortest: Frankiineae corrig. (11 characters)
Average: 15.83 characters
Median: 16.00 characters
Mode: 16 characters (lower), 16 characters (upper)
Longest: Methylobacterium dichloromethanicum subsp. dichloromethanicum (61 characters)
Shortest: Winkia neuii subsp. neuii (25 characters)
Average: 40.49 characters
Median: 40.00 characters
Mode: 40 characters (lower), 40 characters (upper)
Longest: Geobacillus thermodenitrificans subsp. thermodenitrificans (19 characters)
Shortest: Bifidobacterium longum subsp. suis — Bradyrhizobium barranii subsp. apii — Campylobacter lari subsp. lari — Clavibacter xyli subsp. xyli — Lactobacillus yamanashiensis subsp. mali — Leifsonia xyli subsp. xyli — Lentilactobacillus rapi subsp. rapi — Limosilactobacillus reuteri subsp. suis — Nocardiopsis alba subsp. alba corrig. — Rosenbergiella nectarea subsp. apis — Streptococcus equi subsp. equi — Streptococcus infantarius subsp. coli (4 characters)
Average: 9.64 characters
Median: 9.00 characters
Mode: 8 characters (lower), 8 characters (upper)
Longest: Chromobacterieae (16 characters)
Shortest: Proteeae (8 characters)
Average: 12.17 characters
Median: 12.00 characters
Mode: 12 characters (lower), 12 characters (upper)