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Illustration accompanying Rahm's (1937) description
Scientific classification edit
Kingdom: Animalia
Phylum: Tardigrada
Class: Mesotardigrada
Order: Thermozodia
Family: Thermozodiidae
Genus: Thermozodium
T. esakii
Binomial name
Thermozodium esakii
Rahm, 1937[1][2]
Mesotardigrada is located in Japan
Mesotardigrada (Japan)
The type locality and only locality of observation, near Nagasaki, Japan

Mesotardigrada is one of three classes of tardigrades,[3] consisting of a single species, Thermozodium esakii.[4][5][6][7][8][9][10] The animal reportedly has six claws of equal length at each foot. This species was described in 1937 by German zoologist Gilbert Rahm from a hot spring near Nagasaki, Japan. The inability of taxonomists to replicate Rahm's finding has cast doubt on the accuracy of the description, making T. esakii, and by extension the entire class Mesotardigrada, a taxon inquirendum.[11]

Taxonomic ambiguity[edit]

The type specimen Rahm used as the basis of his description has either been lost[12] or it was never preserved in the first place, which Grothman et al. (2017) suggest is consistent with the lax taxonomic standards of the 1930s.[11] Thus, re-examination of the original specimen is not possible. Complicating matters further, the type locality from which Rahm collected his specimen has been destroyed by an earthquake[which?] and subsequent searches for additional specimens matching the original description have been unsuccessful.[11]

Grothman et al. (2017) suggest that Rahm might have observed and misinterpreted a species in the class Heterotardigrada, possibly belonging to the genus Carphania or Oreella.[11]

See also[edit]

  • Salinella – another high rank taxon whose sole member has not been independently verified to exist


  1. ^ "Thermozodium esakii". Integrated Taxonomic Information System.
  2. ^ Nomenclator Zoologicus Record Detail. Retrieved on 17 October 2011.
  3. ^ Namebank Record Detail. (8 August 2003). Retrieved on 17 October 2011.
  4. ^ "ION: Index to Organism Names". Retrieved 10 November 2011.
  5. ^ Data Use Agreement – GBIF Portal. (22 February 2007). Retrieved on 17 October 2011.
  6. ^ 2010 Annual Checklist :: Species details. Catalogue of Life (28 November 2006). Retrieved on 17 October 2011.
  7. ^ 2010 Annual Checklist :: Literature references. Catalogue of Life. Retrieved on 17 October 2011.
  8. ^ "micro*scope – version 6.0 – March, 2006". Archived from the original on 28 September 2011. Retrieved 10 November 2011.
  9. ^ Thermozodium esakii – Encyclopedia of Life[permanent dead link]. EOL. Retrieved on 17 October 2011.
  10. ^ Namebank Record Detail. (8 August 2003). Retrieved on 17 October 2011.
  11. ^ a b c d Grothman, Gary T.; Johansson, Carl; Chilton, Glen; Kagoshima, Hiroshi; Tsujimoto, Megumu; Suzuki, Atsushi C. (February 2017). "Gilbert Rahm and the Status of Mesotardigrada Rahm, 1937". Zoological Science. 34 (1): 5–10. doi:10.2108/zs160109. ISSN 0289-0003. PMID 28148217.
  12. ^ Nelson, Diane R. (2002). "Current Status of the Tardigrada: Evolution and Ecology". Integrative and Comparative Biology. 42 (3): 652–659. doi:10.1093/icb/42.3.652. PMID 21708761.

External links[edit]