[Below is an application to the ICZN submitted 1 December 2025. Comments on this are welcome here. Once this case is published in the ICZN Bulletin comments can be submitted there.]
Proposed conservation of prevailing usage by designation of Mormyrus caschive Linnaeus, 1758 (Osteichthyes, Osteoglossomorpha, MORMYRIDAE) as type species of Mormyrus Linnaeus, 1758
John P. Sullivan1,2*, Christopher Scharpf3
1National Library of Medicine, National Institutes of Health, Bethesda, MD 20894 USA
2Cornell University Museum of Vertebrates, 159 Sapsucker Woods Road, Ithaca, NY 14850 USA (e-mail: jpsullivan@cornell.edu)
3The ETYFish Project, 4102 Westview Road, Baltimore, MD 21218 USA
Abstract. The purpose of this application, under Articles 75.1, 78.1 and 81.1 of the ICZN Code, is to conserve the generic name Mormyrus Linnaeus, 1758 in its prevailing usage by designation of Mormyrus caschive Linnaeus, 1758 as type species. In so doing, we ask the ICZN to use its plenary power to approve two actions: (1) suppress Article 11.6.2 in order to make Mormyrus caschive Linnaeus, 1758, originally proposed in synonymy, an available name consistent with prevailing usage; and (2) set aside the type-species designation for genus Mormyrus Linnaeus, 1758 established in Opinion 77 (1922) and Directions 56 & 57 (1956), which recognize Mormyrus cyprinoides Linnaeus, 1758 instead of Mormyrus caschive Linnaeus, 1758, as the type species. This determination was based on an error in Jordan (1917), later retracted and corrected in a publication not considered by the ICZN (Jordan, 1919). Adherence to Opinion 77 and Directions 56 & 57 would necessitate at least 75 new binominal combinations and destabilize what has been universal nomenclatural practice for more than a century.
Keywords. Nomenclature; taxonomy; Actinopterygii; Osteoglossiformes; MORMYRIDAE; Mormyrus; Mormyrus caschive; Mormyrops anguilloides; Marcusenius; Marcusenius cyprinoides; mormyrids; snoutfish; weakly electric fishes; Africa.
1. Hasselquist (1757, p. 398) described Mormyrus caschive in Iter Palaestinum, a pre-Linnaean rejected work (ICZN Opinion 57) that was posthumously assembled and published by Linnaeus, Hasselquist’s mentor, the year before publication of the tenth edition of Systema Naturae. Hasselquist’s detailed description of Mormyrus caschive corresponds perfectly with the species known today among mormyrid biologists by this name. Particularly noteworthy is the mention of a cylindrical snout acutely sloped downward from the head: “rostrum admodum declive ante verticem capitis acutiusculum, cylindricum” and a fin-ray count of D.80 P.10 V.6 A.19 C.24. These characteristics in combination describe only one of the four recognized Nilotic Mormyrus species (Boulenger, 1907, p. 66; Reizer, 1964, p. 35). Hasselquist described no other mormyrid species in this work.
2. In Systema Naturae Ed. 10. (1758, p. 327) Linnaeus introduced the genus Mormyrus with two included species, both from the Nile, cyprinoides and anguilloides. Under anguilloides, in synonymy, Linnaeus lists “Mormyrus Caschive” of his late student, Hasselquist, citing p. 398 of Hasselquist’s Iter. While type specimens survive of M. cyprinoides and M. anguilloides, no specimen exists for the Mormyrus caschive of Linnaeus (Fernholm & Wheeler 1983, S. Kullander, pers. comm., 2015). Linnaeus’ fin-ray counts for Mormyrus caschive are identical to those reported in Iter with the exception of the dorsal-fin ray count for which Linnaeus reports 20 rays instead of 80. Géry (1968, p. 75) attributed the dorsal-fin ray discrepancy to a typographical omission of the Roman numeral “C” from “XXC.” Valenciennes (1846), who had specimens of Mormyrus caschive at his disposal, considered Linnaeus’ reported dorsal-ray count “une erreur typographique” and expressed puzzlement at how he could have synonymized two species with such different characteristics (Valenciennes in Cuvier and Valenciennes, 1846, p. 237). Linnaeus’ decision to treat Mormyrus caschive as a synonym of the morphologically dissimilar Mormyrus anguilloides suggests to us he lacked a specimen to examine.
3. Whatever the explanation, Linnaeus’ placement of Mormyrus caschive as junior synonym of M. anguilloides in Systema Naturae renders the name unavailable per Article 11.6 of the Code (ICZN, 1999), which stipulates that “A name which when first published in an available work was treated as a junior synonym of a name then used as valid is not thereby made available.” Eschmeyer’s Catalog of Fishes (ECoF), the standard reference for ichthyological nomenclature, preserves Mormyrus caschive, citing Article 11.6.1 (Fricke et al., 2025): “However, if such a name published as a junior synonym had been treated before 1961 as an available name and either adopted as the name of a taxon or treated as a senior homonym, it is made available thereby but dates from its first publication as a synonym.” According to ECoF, M. caschive can be “validated back” to Linnaeus by Walbaum’s inclusion of M. caschive in his Petri Artedi sueci genera piscium (1792, p. 632). Unfortunately, Article 11.6.2 further stipulates that “A name published before 1758 but after 1757 cited as a synonym of a name used as valid cannot be made available under Article 11.6.” Hence, Mormyrus caschive, cited as a synonym of M. anguilloides in 1758, is unavailable. Despite this, ichthyologists have consistently regarded Mormyrus caschive Linnaeus 1758 as a valid name throughout the 20th and 21st centuries (see Appendix).
4. In a footnote to a paper primarily concerning the cichlid genus Hemichromis, Gill (1862, p. 139) designated Mormyrus caschive Hasselquist, 1757 as the type species of Mormyrus. This formulation was followed by others (Jordan 1919, p. 167; Reizer, 1964, p. 5) in crediting the species to Hasselquist; however, as noted above, names in Hasselquist (1757) are unavailable. Furthermore, recognizing Mormyrus caschive Linnaeus, 1758 as the type species of Mormyrus Linnaeus, 1758 contradicts ICZN Opinion 77 (1922) and Directions 56 & 57 (1956), which designate Mormyrus cyprinoides Linnaeus, 1758 as the type species. (Note: We contend that Mormyrus cyprinoides is the type species of Marcusenius, an issue explored in a paper to be published elsewhere.) As stated in Direction 56, this determination relied on Jordan’s designation in Part I of Genera of Fishes (1917, p. 17). Jordan, however, retracted this designation in Part II (1919a, p. 167) in a section entitled “Additions and Corrections to Part I,” stating that Mormyrus caschive Hasselquist “as restricted by Gill” is the type of Mormyrus Linnaeus, “not M. cyprinoides L. as stated in part 1, page 15; this species is the type of Marcusenius Gill.” Unfortunately, the Commission did not account for Jordan’s retraction when issuing Directions 56 & 57.
5. If Opinion 77 and Directions 56 & 57 were to be followed, the valid generic name of all species that mormyrid taxonomists currently place in Marcusenius Gill, 1862 (typified by M. cyprinoides) would move to Mormyrus, treating Marcusenius as a junior synonym. Consequently, species currently recognized in Mormyrus would require a new generic epithet; the oldest available replacement is Scrophicephalus Swainson, 1838 (p. 309) with the type species Mormyrus longipinnis Rüppell, 1832. Such changes would necessitate at least 75 new binomial combinations (Table 1), causing considerable confusion not only for taxonomists but also for neurobiologists, ethologists, and ecologists who have studied the weakly electric properties of these genera for decades. To our knowledge, the only works to follow Opinion 77 and Directions 56 & 57 are the printed edition of Eschmeyer’s Genera of Fishes (Eschmeyer, 1990) and its online successor, the Catalog of Fishes (ECoF). However, the online ECoF is inconsistent: while it cites Mormyrus cyprinoides as the type species of Mormyrus, it simultaneously classifies the species itself within Marcusenius. Similarly, it cites Mormyrus anguilloides Linnaeus, 1758 as the type species of Marcusenius, despite classifying that species within Mormyrops. Aside from these contradictory database entries, we are unaware of any publication that treats Mormyrus cyprinoides as the type species of Mormyrus, or that treats Mormyrus caschive as an unavailable name. Conversely, we identified 60 publications across various disciplines that use the combination Mormyrus caschive post Opinion 77 (Appendix) and five taxonomic works that explicitly recognize Mormyrus caschive as the type species of genus Mormyrus (Reizer, 1964, p. 35; Géry, 1968, p. 75; Taverne, 1972, p.163; Roberts & Stewart, 1976, p. 268; Gosse, 1984, vol. 1, p. 99)
6. While mormyrid taxonomists universally treat Mormyrus caschive Linnaeus, 1758 as the type species of Mormyrus, no type specimen has been found in the Swedish Museum of Natural History (Fernholm & Wheeler, 1983; S. Kullander, pers. comm. 2015). Given the importance of stability for the type species of the nominal genus for the family MORMYRIDAE, the designation of a neotype is warranted to objectively define the taxon. We intend to propose such a designation in a separate publication once the availability of the name Mormyrus caschive Linnaeus, 1758 is confirmed by the Commission.
7. The International Commission on Zoological Nomenclature is accordingly asked:
(1) to use its plenary power:
- (a) to suppress Article 11.6.2 for the purposes of this Case to rule that the specific name caschive Linnaeus, 1758, proposed in the binomen Mormyrus caschive Linnaeus, 1758, is not to be treated as unavailable by reason of having been published as a junior synonym;
- (b) to set aside all previous fixations of type species for the nominal genus Mormyrus Linnaeus, 1758 and to designate Mormyrus caschive Linnaeus, 1758 as the type species;
(2) to place on the Official List of Generic Names in Zoology the name Mormyrus Linnaeus, 1758 (gender: masculine), type species Mormyrus caschive Linnaeus, 1758, as designated in (1)(b) above;
(3) to place on the Official List of Specific Names in Zoology the name caschive Linnaeus, 1758, as published in the binomen Mormyrus caschive and as ruled in (1)(a) above (specific name of the type species of Mormyrus Linnaeus, 1758);
(4) to place on the Official Index of Rejected and Invalid Specific Names in Zoology the name caschive Hasselquist, 1757, as published in the binomen Mormyrus caschive (published in a work rejected for nomenclatural purposes).
Acknowledgments
We are grateful to the late William Eschmeyer, Kai Heller, Maurice Kottelat and attendees of the 6th meeting of the Pan African Fish and Fisheries Association in Mangochi, Malawi, 24–28 September 2018 for fruitful discussions on nomenclatural problems in MORMYRIDAE.
References
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Table 1. Nomenclatural changes affecting currently valid mormyrid taxa if ICZN Opinion 77 and Directions 56 & 57 were to be followed.
Prevailing usage among mormyrid taxonomists New combinations required by ICZN Opinion 77 and Directions 56 & 57
Marcusenius abadii (Boulenger 1901) Mormyrus abadii (Boulenger 1901)
Marcusenius altisambesi Kramer, Skelton, van der Bank & Wink 2007 Mormyrus altisambesi (Kramer, Skelton, van der Bank & Wink 2007)
Marcusenius angolensis (Boulenger 1905) Mormyrus angolensis (Boulenger 1905)
Marcusenius annamariae (Parenzan 1939) Mormyrus annamariae (Parenzan 1939)
Marcusenius bentleyi (Boulenger 1897) Mormyrus bentleyi Boulenger 1897
Marcusenius brucii (Boulenger 1910) Mormyrus brucii (Boulenger 1910)
Marcusenius caudisquamatus Maake, Gon & Swartz 2014 Mormyrus caudisquamatus (Maake, Gon & Swartz 2014)
Marcusenius cuangoanus (Poll 1967) Mormyrus cuangoanus (Poll 1967)
Marcusenius cyprinoides (Linnaeus 1758) Mormyrus cyprinoides Linnaeus 1758
Marcusenius deboensis (Daget 1954) Mormyrus deboensis (Daget 1954)
Marcusenius desertus Kramer, van der Bank & Wink 2016 Mormyrus desertus (Kramer, van der Bank & Wink 2016)
Marcusenius devosi Kramer, Skelton, van der Bank & Wink 2007 Mormyrus devosi (Kramer, Skelton, van der Bank & Wink 2007)
Marcusenius dundoensis (Poll 1967) Mormyrus dundoensis (Poll 1967)
Marcusenius elegans Fricke & Kramer 2022 Mormyrus elegans (Fricke & Kramer 2022)
Marcusenius friteli (Pellegrin 1904) Mormyrus friteli (Pellegrin 1904)
Marcusenius furcidens (Pellegrin 1920) Mormyrus furcidens (Pellegrin 1920)
Marcusenius fuscus (Pellegrin 1901) Mormyrus fuscus (Pellegrin 1901)
Marcusenius ghesquierei (Poll 1945) Mormyrus ghesquierei (Poll 1945)
Marcusenius greshoffii (Schilthuis 1891) Mormyrus greshoffii Schilthuis 1891
Marcusenius intermedius Pellegrin 1924 Mormyrus intermedius (Pellegrin 1924)
Marcusenius kainjii Lewis 1974 Mormyrus kainjii (Lewis 1974)
Marcusenius kaninginii Kisekelwa, Boden, Snoeks & Vreven 2016 Mormyrus kaninginii (Kisekelwa, Boden, Snoeks & Vreven 2016)
Marcusenius krameri Maake, Gon & Swartz 2014 Mormyrus krameri (Maake, Gon & Swartz 2014)
Marcusenius kutuensis (Boulenger 1899) Mormyrus kutuensis (Boulenger 1899)
Marcusenius lambouri (Pellegrin 1904) Mormyrus lambouri (Pellegrin 1904)
Marcusenius leopoldianus (Boulenger 1899) Mormyrus leopoldianus (Boulenger 1899)
Marcusenius livingstonii (Boulenger 1899) Mormyrus livingstonii (Boulenger 1899)
Marcusenius lucombesi Maake, Gon & Swartz 2014 Mormyrus lucombesi (Maake, Gon & Swartz 2014)
Marcusenius macrolepidotus (Peters 1852) Mormyrus macrolepidotus Peters 1852
Marcusenius macrophthalmus (Pellegrin 1924) Mormyrus macrophthalmus (Pellegrin 1924)
Marcusenius mento (Boulenger 1890) Mormyrus mento Boulenger 1890
Marcusenius meronai Bigorne & Paugy 1990 Mormyrus meronai (Bigorne & Paugy 1990)
Marcusenius monteiri (Günther 1873) Mormyrus monteiri Günther 1873
Marcusenius moorii (Günther 1867) Mormyrus moorii Günther 1867
Marcusenius multisquamatus Kramer & Wink 2013 Mormyrus multisquamatus (Kramer & Wink 2013)
Marcusenius ntemensis (Pellegrin 1927) Mormyrus ntemensis (Pellegrin 1927)
Marcusenius pongolensis (Fowler 1934) Mormyrus pongolensis (Fowler 1934)
Marcusenius sanagaensis Boden, Teugels & Hopkins 1997 Mormyrus sanagaensis (Boden, Teugels & Hopkins 1997)
Marcusenius schilthuisiae (Boulenger 1899) Mormyrus schilthuisiae (Boulenger 1899)
Marcusenius senegalensis (Steindachner 1870) Mormyrus senegalensis Steindachner 1870
Marcusenius senegalensis gracilis (Pellegrin 1922) Mormyrus senegalensis gracilis (Pellegrin 1922)
Marcusenius senegalensis pfaffi (Fowler 1958) Mormyrus senegalensis pfaffi (Fowler 1958)
Marcusenius stanleyanus (Boulenger 1897) Mormyrus stanleyanus Boulenger 1897
Marcusenius thomasi (Boulenger 1916) Mormyrus thomasi (Boulenger 1916)
Marcusenius ussheri (Günther 1867) Mormyrus ussheri Günther 1867
Marcusenius verheyenorum Mambo Baba, Kisekelwa, et al. 2020 Mormyrus verheyenorum (Mambo Baba, Kisekelwa, et al. 2020)
Marcusenius victoriae (Worthington 1929) Mormyrus victoriae (Worthington 1929)
Marcusenius wamuinii Decru, Sullivan & Vreven 2019 Mormyrus wamuinii (Decru, Sullivan & Vreven 2019)
Mormyrus bernhardi Pellegrin 1926 Scrophicephalus bernhardi (Pellegrin 1926)
Mormyrus caballus Boulenger 1898 Scrophicephalus caballus (Boulenger 1898)
Mormyrus caballus asinus Boulenger 1915 Scrophicephalus caballus asinus (Boulenger 1915)
Mormyrus caballus bumbanus Boulenger 1909 Scrophicephalus caballus bumbanus (Boulenger 1909)
Mormyrus caballus lualabae Reizer 1964 Scrophicephalus caballus lualabae (Reizer 1964)
Mormyrus casalis Vinciguerra 1922 Scrophicephalus casalis (Vinciguerra 1922)
Mormyrus caschive Linnaeus 1758 Scrophicephalus caschive (Linnaeus 1758)
Mormyrus cyaneus Roberts & Stewart 1976 Scrophicephalus cyaneus (Roberts & Stewart 1976)
Mormyrus felixi Pellegrin 1939 Scrophicephalus felixi (Pellegrin 1939)
Mormyrus goheeni Fowler 1919 Scrophicephalus goheeni (Fowler 1919)
Mormyrus hasselquistii Valenciennes 1847 Scrophicephalus hasselquistii (Valenciennes 1847)
Mormyrus hasselquistii guentheri Boulenger 1899 Scrophicephalus hasselquistii guentheri (Boulenger 1899)
Mormyrus hildebrandti Peters 1882 Scrophicephalus hildebrandti (Peters 1882)
Mormyrus iriodes Roberts & Stewart 1976 Scrophicephalus iriodes (Roberts & Stewart 1976)
Mormyrus kannume Fabricius 1775 Scrophicephalus kannume (Fabricius 1775)
Mormyrus lacerda Castelnau 1861 Scrophicephalus lacerda (Castelnau 1861)
Mormyrus longirostris Peters 1852 Scrophicephalus longirostris (Peters 1852)
Mormyrus macrocephalus Worthington 1929 Scrophicephalus macrocephalus (Worthington 1929)
Mormyrus macrophthalmus Günther 1866 Scrophicephalus macrophthalmus (Günther 1866)
Mormyrus niloticus (Bloch & Schneider 1801) Scrophicephalus niloticus (Bloch & Schneider 1801)
Mormyrus ovis Boulenger 1898 Scrophicephalus ovis (Boulenger 1898)
Mormyrus proboscirostris Boulenger 1888 Scrophicephalus proboscirostris (Boulenger 1888)
Mormyrus rume Valenciennes 1847 Scrophicephalus rume (Valenciennes 1847)
Mormyrus subundulatus Roberts 1989 Scrophicephalus subundulatus (Roberts 1989)
Mormyrus tapirus Pappenheim 1905 Scrophicephalus tapirus (Pappenheim 1905)
Mormyrus tenuirostris Peters 1882 Scrophicephalus tenuirostris (Peters 1882)
Mormyrus thomasi Pellegrin 1938 Scrophicephalus thomasi (Pellegrin 1938)
Appendix 1. List of 60 publications published since 1918 recognizing Mormyrus caschive as a valid taxon. Relevant page(s) indicated in brackets.
1. Abu Gideiri YB (1967) Fishes of the Blue Nile, between Khartoum and Roseires. Revue de Zoologie et Botanique Africaine, 76 (3–4): 345–348. [p. 348]
2. Adam A (1975) Observations on the commercial fish in Lake Nubia. Sudan Notes and Records 56: 261–268. [p. 265]
3. Akoth D, Natugonza V, Efitre J, Muyodi FJ, Musinguzi L (2023) The non-Haplochromis fish fauna in Uganda: an update on the distribution and a review of data gaps. Environmental Monitoring and Assessment 195 (412): 1–24. [p. 411] https://link.springer.com/article/10.1007/s10661-023-11014-1
4. Bailey RG (1994) Guide to the fishes of the River Nile in the Republic of the Sudan. Journal of Natural History, 28, pp. 937-970. [p. 942] https://doi.org/10.1080/00222939400770501
5. Baron VD, Golubtsov AS, Orlov AA (2017) Phase locking and phase avoidance behavior in eleven Nilotic mormyrid species (MORMYRIDAE, Mormyriformes) in response to external electrical stimuli. Journal of Ichthyology 57: 617–624. [p. 349] https://link.springer.com/article/10.1134/S0032945217040014
6. Bertin L (1940) Catalogue des types de Poissons du Muséum national d'Histoire naturelle. 2e partie. Dipneustes, Chondrostéens, Holostéens, Isospondyles. Bulletin du Muséum national d'histoire naturelle. (Série 2) v. 12 (no. 6): 244-322. [p. 268] https://www.biodiversitylibrary.org/part/329817
7. Bishaï RM (1967) Part I. Osteology of Mormyrus cashive (L.). The Skull. Part II. Vertebral column, Girdles and Fins. Anatomischer Anzeiger, 120: 375–397. [p. 375]
8. Blache J (1964) Les poissons du bassin du Tchad et du bassin adjacent du Mayo Kebbi étude systématique et biologique. Mémoire publié sous le Haut Patronage de Monsieur le Chef de l’État Président du Conseil de la République du Tchad, ORSTOM, Paris. 483 pp. [p. 35] https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes...
9. Boessneck J (1982) Studien an subfossilen Tierknochen aus Ägypten. München: Deutscher Kunstverlag. 172 pp. 15 pl. [p. 14] https://www.ugarit-verlag.com/products/studien-an-subfossilen-tierknoche...
10. Borodi CM, Akoll P, Masette M, Mulinda S (2022) Effect of smoking technologies on nutritional quality and polycyclic aromatic hydrocarbon levels in smoked Mormyrus caschive and Oreochromis niloticus of Terekeka, South Sudan African Journal of Food Science 16 (1): 1–9. [p. 2] https://doi.org/10.5897/AJFS2021.2155
11. Bwaku Wandera S, Balirwa JS (2010) Fish species diversity and relative abundance in Lake Albert—Uganda. Aquatic Ecosystem Health & Management, 13 (3): 284–293. [p. 286] https://doi.org/10.1080/14634988.2010.507120
12. Daget J, Durand JR (1981) Poissons [pp. 687–771, 96 fig., 24 pl.] In: Durand J.R. & Lévêque C. (eds), Flore et faune aquatiques de l'Afrique Sahelo-Soudanienne. Tome II. Éditions de l'ORSTOM, Coll. Init. Doc. Techn. 45: 391-873. [p. 709] https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2024-07/00347...
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Below is a draft of an earlier version of the application.
Mormyrus Linnaeus, 1758, Mormyrops Müller, 1843, and Marcusenius Gill, 1862 (Teleostei, Osteoglossiformes): proposed conservation of prevailing usage by designation of Mormryus caschive Linnaeus, 1758 as type species of Mormyrus Linnaeus, 1758, Mormyrus anguilloides Linnaeus, 1758 as type species of Mormyrops Müller, 1843, Mormyrus cyprinoides Linnaeus, 1758 as type species of Marcusenius Gill, 1862 and a proposed designation of a neotype for Mormyrus caschive Linnaeus, 1758.
John P. Sullivan
Cornell University Museum of Vertebrates, 159 Sapsucker Woods Rd., Ithaca, New York, USA (e-mail: jpsullivan@cornell.edu)
Abstract. The purpose of this application, under Articles 11.6.1, 75.1, 78.1 and 81.1 [?] of the Code, is to conserve the generic name Mormyrus Linnaeus, 1758 in its prevailing usage by designation of Mormyrus caschive Linnaeus, 1758 as type species. This requires reversing the Commission’s Opinion 77 (1917) and Directions 56 & 57 (1956) that recognized Mormyrus cyprinoides Linnaeus, 1758 as the type species of genus Mormyrus Linnaeus, 1758. This determination was based on an error in Jordan (1917) retracted and corrected in Jordan (1919a). This correction was never reflected in a revision of the ICZN’s ruling. As no type specimen exists, we propose designating BMNH 1862.6.17.18 as neotype of Mormyrus caschive Linnaeus, 1758. Furthermore, while prevailing usage now treats Mormyrus cyprinoides Linnaeus, 1758 as the type species of Marcusenius Gill, 1862 and Mormyrus anguilloides Linnaeus, 1758 as the type species of Mormyrops Müller, these designations were made in a key presented in Gill (1862) in which the author reversed the two names counter to his obvious intention. I propose that to avoid future confusion and promote stability, the type designations reflecting current usage be entered on the Official List.
Keywords. Nomenclature; taxonomy; Actinopterygii; Osteoglossiformes; Mormyridae; Mormyrus; Mormyrops; Marcusenius; Mormyrus caschive; Mormyrops anguilloides; Marcusenius cyprinoides; mormyrids; snoutfish; weakly electric fishes; Africa.
1. The purpose of this petition is to correct and clarify longstanding, related nomenclatural issues within the African weakly electric fish family Mormyridae (Teleostei, Osteoglossiformes). Current practice in mormyrid taxonomy universally assumes
• The type species of genus Mormyrus Linnaeus, 1758 is Mormyrus caschive Linnaeus, 1758
• The type species of genus Mormyrops Müller, 1843 is Mormyrus anguilloides Linnaeus, 1758
• The type species of genus Marcusenius Gill, 1862 is Mormyrus cyprinoides Linnaeus, 1758
However, on the ICZN Official List (Opinion 77, Direction 56, Direction 57), Mormyrus cyprinoides Linnaeus, 1758 is given as the type species of Mormyrus, not Mormyrus caschive. Accordingly, the valid generic name of Marcusenius species in the current sense is Mormyrus and therefore the species currently treated as Mormyrus require a new generic epithet. The oldest available synonym is Scrophicephalus Swainson, 1838 (p. 309) with the type species Mormyrus longipinnis Rüppell, 1832. An attempt to impose the ICZN’s existing ruling on mormyrid generic nomenclature—changing all 66 binomial combinations for the valid species of the two genera—would create enormous confusion and instability. Additionally, while usage today is uniform, there is a history of confusion as to the identity of the type species of Mormyrops Müller, 1843 and Marcusenius Gill, 1862. These issues are unresolved in the Catalog of Fishes (Eschmeyer 2015), the standard reference for ichthyological nomenclature, that indicates that Mormyrus anguilloides Linnaeus, 1758 is type species for both Mormyrops Müller 1843 and Marcusenius Gill 1862. This would imply that Marcusenius Gill 1862 is an objective junior synonym of Mormyrops Müller, 1843. Below I lay out the case that (1) ICZN's ruling on the type species for Mormryus Linnaeus followed a mistake by D.S. Jordan in Part I of his Genera of Fishes (1917) that Jordan himself later corrected and (2) confusion regarding the type species of Marcusenius Gill is due to an error, recognized as such by some, but not by others, in a key by Gill (1862) that introduced the generic name Marcusenius and designated a type species for it and for Mormyrops Müller. These issues form a "veritable Gordian knot" of generic names and type species within this family (Myers, 1960, p. 123) which to untie must be treated together. I recommend actions for the ICZN that will clarify the nomenclature of this group.
2. Mormyrus. Hasselquist (1757, p. 398) described Mormyrus caschive in Iter Palaestinum, a pre-Linnaean rejected work (ICZN Opinion 57) that was posthumously assembled and published by Linnaeus, Hasselquist’s mentor, the year before publication of the tenth edition of Systema Naturae. Hasselquist’s detailed description of Mormyrus caschive corresponds perfectly with the species we know today by this name. Particularly noteworthy is the mention of a cylindrical snout acutely sloped downward from the head: “rostrum admodum declive ante verticem capitis acutiusculum, cylindricum” and a fin-ray count of D.80 P.10 V.6 A.19 C.24. These characteristics in combination describe only one of the four recognized Nilotic Mormyrus species (Boulenger, 1907, p.66; Reizer 1964, p. 35). Hasselquist described no other mormyrid species in this work.
3. In Systema Naturae Ed. 10. (1758, p. 327) Linnaeus introduced the genus Mormyrus with two included species, both from from the Nile, cyprinoides and anguilloides. Under anguilloides, in synonymy, Linnaeus lists “Mormyrus Caschive” of his late student, Hasselquist, citing p. 398 of Hasselquist’s Iter. While type specimens survive of M. cyprinoides and and M. anguilloides, no specimen exists for the Mormyrus caschive of Linnaeus (Ferhholm & Wheeler 1983, S. Kullander, pers. comm. 2015). Linnaeus’ fin-ray counts for Mormyrus caschive are identical to those reported in Iter with the exception of the dorsal-fin ray count for which Linnaeus reports 20 rays instead of 80. It may be that Linnaeus’ decision to treat Mormryus caschive as a synonym of Mormyrus anguilloides and the disparity in the dorsal-fin ray counts were related to his not having a specimen of Mormyrus caschive to examine. (Géry (1968) suggested that the dorsal-fin ray count error could be due from a simple typographical ommission of the Roman numeral "C" from the original "XXC.") Valenciennes (1846), who had specimens of Mormryus caschive at his disposal, considered Linnaeus’ dorsal-ray count of this species “une erreur typographique” and expressed puzzlement at how Linnaeus could have synonymized the two species with such different characteristics (Valenciennes in Cuvier and Valenciennes, 1846, p. 237). Whatever his reasons for doing so, Linnaeus’ synonymy of Mormyrus caschive with M. anguilloides in Systema Naturae renders the name unavailable (ICZN 11.6). However, following Article 11.6.1 of the Code, the name is validated back to Linnaeus by Walbaum's inclusion of Mormyrus caschive in his Petri Artedi sueci genera piscium (1792, p. 632). Mormyrus caschive was similarly treated as a valid species in a number of other early ichthyological works, e.g. Bloch and Schneider, 1801, p. 456; Rüppel, 1829, p.4; and Valenciennes in Cuvier and Valenciennes, 1846, p. 227. [Note: I no longer believe this interpretation is correct. Article 11.6.2 of the Code makes clear that Mormyrus caschive is simply an unavailable name. ~ JPS 7/2022]
4. In a footnote to an 1862 paper concerned primarily with species of the Cichlidae genus Hemichromis that we will revisit below with regard to genera Momryrops and Marcusenius, Gill (1862, p. 139) designated Mormyrus caschive Hasselquist, 1757 as the type species of Momryrus and this formulation was followed by others (Jordan 1919a, p. 167; Reizer, 1964, p. 5) in crediting the species to Hasselquist. However, as noted above, names in Hasselquist, 1757 are unavailable and the name is validated back to Linnaeus, 1758 via Walbaum (1792). Thus, the correct citation for this species is "Mormyrus caschive Linnaeus, 1758." Over the past 50 years most authors (e.g. Taverne, 1972, p.163; Roberts & Stewart, 1976, p. 268; Gosse 1984, vol. 1, p. 99; Catalog of Fishes, 2014) have used this latter, correct formulation. However, recognition of Mormyrus caschive Linnaeus, 1758 as the type species of Mormyrus Linnaeus, 1758 contradicts ICZN Opinion 77 (1917) and Direction 56 & 57 (1956) that recognize Mormyrus cyprinoides Linnaeus, 1758 to be the type species of Mormyrus Linnaeus, 1758. As stated in Direction 56, this determination was based on Jordan’s determination in Part I of Genera of Fishes (1917, p. 17). Jordan, however, retracted this designation in Part II of Genera of Fishes (1919a, p. 167) in a section entitled “Additions and Corrections to Part I,” indicating that Mormyrus caschive Hasselquist “as restricted by Gill” is the type of Mormyrus Linnaeus, “not M. cyprinoides L. as stated in part 1, page 15; this species is the type of Marcusenius Gill.” The ICZN never amended its original ruling. A revised ruling and entry on the Official List is needed to achieve accord with prevailing usage.
5. While the availability of Mormyrus caschive Linnaeus, 1758 is rescued by its use in Walbaum 1792 [see note added to #3 above], no type specimen has been found for it in the Swedish Museum of Natural History by either Fernholm & Wheeler (1983) or more recently by Senior Curator of Fishes Sven Kullander (2015, pers comm.). As stability of this taxon—the type species of the nominal genus for family Mormyridae—is highly desirable, we believe designation of a neotype is warranted. A most suitable specimen, apparently female and 520 mm standard length, is housed at the Natural History Museum, London under accession number BMNH 1862.6.17.18. This specimen is cited as an exemplar of this species in two important works (Günther 1866, Boulenger 1907) and remains in excellent condition despite being more than 150 years old (Fig. 1). It is first cited in Günther (1866, p. 215) as one of “two fine specimens” collected in Khartoum by John Petherick, British Consul to the Sudan (the other is BMNH 1862.6.17.75.) It also appears as the fourth of 14 specimens presented in a table of counts and measurements in Boulenger’s Fishes of the Nile (1907, p. 67), and is the one Boulenger chose for a representative illustration of the species (Fishes of the Nile, plate XII.2). Boulenger’s detailed description of this species (1907, p.66), based in part on this specimen we propose as neotype, obviates the need to repeat a description here.
6. Mormyrops and Marcusenius. Müller (1843, p. 324) published the new genus-group name Mormyrops in Beiträge zur Kenntniss der natürlichen Familien der Fische, in which he included the species Mormyrus anguilloides Linnaeus 1758 and Mormyrus labiatus of Geoffroy Saint-Hilaire 1809, without designating a type. It would fall to Gill (1862, p. 139) to designate a type species for Mormyrops Müller. By this time, Valenciennes in Cuvier and Valenciennes, 1846, p. 266, had synonymized Mormyrus labiatus Geoff. with Mormyrus cyprinoides L. Marcusen (1854, p. 6, p. 14) had recognized this synonymy and used the combination Mormyrops cyprinoides. Gill's intention was to designate the senior synonym, at that time properly Mormyrops cyprinoides (Linnaeus 1758), as type of Mormyrops Müller and Mormyrops anguilloides (Linnaeus 1758) as type of his new genus Marcusenius. Unfortunately, Gill would inadvertently switch the names anguilloides and cyprinoides in the key presented in the 1862 footnote and this error would go on to establish current usage. Gill's intention and his error are made clear by the following observations. In his 1862 footnote, Gill (1862, p. 139) introduced the new mormyrid genus and species Marcusenius brachyistius, but did not designate this new species as type species of Marcusenius. First, Gill states that the new Marcusenius brachyistius is a “congener” of “M. anguilloides, M. Tuckeyi and M. zambanenje” (all species of Mormyrops in the current sense) and then produces a key to genera that reads (inconsistent use of parentheses retained):
Lower jaw prominent, M. anguilloides. L . . . Mormyrops.
Upper jaw longer, (M. cyprinoides L.) . . . . Marcusenius.
In this key the new genus Marcusenius is not associated with anguilloides, the aforementioned "congener" of Marcusenius brachyistius, and "lower jaw prominent" and "upper jaw longer" are mismatched with the indicated species (M. cyprinoides has a prominent lower jaw, not M. anguilloides). A subsequent publication in which Gill reiterated his generic concepts (Gill 1863, p. 443) removes any possible doubt as to his intention. Here Gill reproduces the couplet above in a new key in which anguilloides and cyprinoides have changed positions and then explicitly indicates the type species for the two genera as follows:
MARCUSENIUS Gill.
Marcusenius anguilloides = Mormyrus anguilloides Linn.
MORMYROPS Müller.
Mormyrops cyprinoides = Mormyrus cyprinoides Linn. (nec Geoffroy.)
Clearly Gill had meant to designate anguilloides as type of his new genus Marcusenius and cyprinoides as type of Mormyrops Müller in the 1862 footnote.
7. Gill’s inadvertent association of Mormyrops with anguilloides and Marcusenius with cyprinoides in his 1862 key determined later usage of these genus-group names, particularly after these were accepted at face value and reiterated by Jordan in parts II & III of his Genera of Fishes (1919a,b). Jordan (1919a, p. 216) recognized Mormyrus anguilloides as the type of Mormyrops Müller (although strangely assigned authorship of Mormyrus anguilloides to Geoffroy St. Hilaire instead of Linnaeus and wrongly attributed the type designation to Müller (1843) who made no such designation). In the following volume (1919b, p.314) Jordan recognized Mormyrus cyprinoides Linnaeus as the type species of Marcusenius Gill, 1862. Prior to Jordan 1919, Boulenger had likewise implicitly considered the anguilloides of Linnaeus the type species of Mormyrops Müller, but treated Marcusenius brachyistius Gill as the type species of Marcusenius Gill (e.g. Boulenger 1899, p. 792; 1909, p. 60) without justification. Boulenger classified the cyprinoides of Linnaeus and other species with globlular swellings or barbels on the lower jaw as Gnathonemus Gill 1863 (type species Mormyrus petersii Günther 1862). Many continued to follow Boulenger's usage post-Jordan 1919 (e.g. Daget 1954, p. 94; David & Poll 1937, Pellegrin 1927, Poll 1939, 1969; Schultz 1942, p. 309; see discussion in Géry, 1968). However, Géry (1968, p. 75), Taverne (1968, p. 86; 1971a, p. 102; 1971b, p. 5; 1972, p. 165) and Gosse (1984, p. 80), following Jordan, not Boulenger, cite the unintentional type species assignment in Gill (1862, p. 139) for Marcusenius and solidified subsequent usage (e.g. Boden et al. 1997, p. 1646; Harder 2000, no pagination; Hopkins et al. 2007, p. 281; Jegu & Lévèque 1984, p. 335; Kramer 2013a, Kramer 2013b, Maake et al., 2014, Roberts & Stewart 1976; Teugels et al. 2001, p. 239.)
8. For the purpose of fixation of type species, Gill's intention in his 1862 publication, made clear in his subsequent 1863 publication, may be irrelevent, since according to the Code the first nomenclatural act taken in respect of a name to achieve fixation of a type species constitutes the only valid such act (ICZN Art. 23.6).* Nonetheless, it is remarkable that so few have recognized that Gill's error was in the first (1862, p. 139) publication. Placing the error in the second (1863, p. 444) publication, Jordan (1919b, p.314) noted that Gill had "by some confusion" transferred the name Marcusenius to Mormyrus anguilloides L. and in agreement Géry (1968, p. 74) says of Gill 1863 p. 444 "il ait interverti par mégarde les espèçes-types de Marcusenius et Mormyrops." Only Eschmeyer (2015) in the Catalog of Fishes entry for genus Marcusenius correctly identifies the locus of the error in Gill 1862 (p. 139) and adheres to Gill's intention in recognizing Mormyrus anguilloides Linnaeus 1758 type of Marcusenius Gill. Eschmeyer's entry notes that Taverne (1972, p. 165) treats the genus Marcusenius as valid "but apparently with wrong type." Strangely, however, the Catalog of Fishes also lists Mormyrus anguilloides Linnaeus 1758 as type of Mormyrops Müller without discussion. Thus, despite current uniformity of usage, confusion lingers regarding the type species of Marcusenius Gill. Although there has been no controversy or confusion in practice regarding the type species of Mormyrops Müller, (all workers post-Gill have treated Mormyrus anguilloides Linnaeus as the implicit or explicit type, in accord with the erroneous type assignment in Gill's 1862 key, contra Gill 1863), a careful reading of Gill's two publications detailed above could destabilize its nomenclature in the future.
9. In order to promote stability of these three genus-group names in Mormryridae, the International Commission on Zoological Nomenclature is accordingly asked:
(1) to rule that the specific name Mormyrus caschive was made available by Walbaum (1792) that validates the name back to Linnaeus, 1758.
(2) to use its plenary power to set aside all previous fixations of name-bearing type for caschive Linnaeus, 1758 as published in the binomen Mormyrus caschive and to designate as neotype specimen BMNH 1862.6.17.18, female, in the Natural History Museum, London;
(3) to use its plenary power to set aside to set aside all previous fixations of type species for the nominal genus Mormyrus Linnaeus, 1758 (Opinion 77 & Direction 56, Direction 57) and to designate Mormyrus caschive Linnaeus, 1758 as the type species.
(4) to use its plenary power to set aside all previous fixations of type species for the nominal genus Mormyrops Müller, 1843 and to designate Mormyrus anguilloides Linnaeus, 1758 as the type species.
(5) to use its plenary power to set aside all previous fixations of type species for the nominal genus Marcusenius Gill, 1862 and to designate Mormyrus cyprinoides Linnaeus, 1758 as the type species.
(6) to emend the entry on the Official List of Generic Names in Zoology for the name Mormyrus Linnaeus, 1758 (gender masculine) to indicate type species Mormyrus caschive Linnaeus, 1758 as ruled in (3) above.
(7) to place on the Official List of Generic Names in Zoology the following names:
(a) Mormyrops Müller, 1843 (gender masculine), type species Mormyrus anguilloides Linnaeus, 1758 as ruled in (4) above;
(b) Marcusenius Gill, 1862 (gender masculine), type species Marcusenius cyprinoides Linnaeus, 1758 as ruled in (5) above;
(8) to emend the entry on the Official List of Specific Names in Zoology for the name cyprinoides Linnaeus, 1758 as published in the binomen Mormyrus cyprinoides Linnaeus, 1758 (specific name of the type species of Mormyrus Linnaeus, 1758) as ruled in (3) above.
(9) to place on the Official List of Specific Names in Zoology the following names:
(a) caschive Linnaeus, 1758, as published in the binomen Mormyrus caschive, the specific name of the type species of Mormyrus Linnaeus, 1758;
(b) anguilloides Linnaeus, 1758, as published in the binomen Mormyrus anguilloides, the specific name of the type species of Mormyrops Müller, 1843;
* [How strict is this when intention of author is clearly contrary to an error in the text? Apparently Eschmeyer thought Gill's intention should be followed, not the error in the text.]
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