Ad Konings, 2012
Cichlid Room Companion

Maylandia or Metriaclima, ...again!

By , 2005. image

Classification: Taxonomy and phylogeny, Lake Malawi.

" Strong arguments about the correct name for the zebra complex from lake Malawi "

Metriaclima greshakei A male Metriaclima greshakei (suggested as type species of the subgenus Maylandia) at Makokola, Lake Malawi. Photo by Ad Konings.

The problem still is whether we should use Metriaclima or Maylandia for the zebra complex of Pseudotropheus. A while ago I read on the internet that the description of Metriaclima was "more correct" than that of Maylandia and that this was the reason that we should use that name. This is nonsense. There are no gray zones or personal opinions in species descriptions; a name is either valid (=available) or invalid (=unavailable) or, in Latin, nomen nudum, which means "naked name".

So, who decides if a name is valid? I have read several comments on the problem in which the sole reason we should use the name Maylandia is the fact that highly-acclaimed ichthyologists approved the description. This is nonsense; we should also not forget that a good ichthyologist is not automatically a good nomenclaturist. Should we accept a name because it is used by many ichthyologists in the field? No, also this is incorrect. Should we accept a name because we personally agree with the description and/or its authors? Should we accept a name because nobody has ever contested its validity? Should we accept a name because the Pope decreed it was valid? All these "reasons" are incorrect.

In order to avoid these problems a set of rules (requirements) were set up according to which every description must comply. These rules, the International Code of Zoological Nomenclature, or short, the Code, were set up in 1962 and they apply to descriptions published after the 1st of January 1930. Anything described before that date is not restricted to the rules. Logically, the Code was not perfect the first time it was published and updates have been made frequently by the International Committee of Zoological Nomenclature. Today we are in the 4th edition of the Code. At the publication date of a description it has to follow the rules that are active at the same time. It seems logic that we cannot apply rules that became active in the year 2000 to invalidate a description that was made in 1980 when at that time it complied with the Code. At the time of publication the current version of the Code has to be applied, but if the validity of a description is contested at a much later date we have to consider also the rules that are active at that later point in time. In some cases this could save the validity of a description if new options in the Code have been implemented.

The problem of Maylandia was at first not noticed, probably because the name itself was rather infrequently used so that little attention was given to its description. Since the description is not very long I give here the full text.

Maylandia n. subgen. Espèce type: Pseudotropheus (Maylandia) greshakei Etymology: Le sous-genre est nommé en l'honneur de Hans J. Mayland, Oberursel.
Le sous-genre diffère en plusieurs points de l'espèce-type de Pseudotropheus, Ps. williamsi, dont la description complémentaire précède ce travail dans ce même fascicule (Trewavas: 97). Chez cette espèce, les dents des mâchoires sont disposées régulièrement en bandes incurvées, les dents pharyngiennes peu serrées et relativement grosses, et le patron mélanique du corps consiste en rangées longitudinales de taches ou lignes brisées, au lieu de barres verticales. Quelques autres espèces de Pseudotropheus, s. lat. ressemblent à Ps. greshakei et diffèrent de Ps. williamsi par les rangées internes de dents moins régulières et, au moins chez les adultes, comprenant beaucoup d'unicuspides, les dents pharyngiennes fines et très serrées postérieurement, et le patron mélanique du corps formant des barres verticales plus ou moins voyantes. Telles sont Ps. zebra Boulenger, Ps. aurora Burgess, Ps. lombardoi Burgess et Ps. livingstonii Boulenger. Les deux dernières espèces ont, chez les femelles et les mâles non territoriaux, un patron bien défini de six barres verticales sur le corps dont 5 s'étendent sur la dorsale et s'amenuisent jusqu'à disparaître sur la portion inférieure des flancs. Ps zebra et les nombreuses formes apparentées ont des barres verticales, comme chez Ps. greshakei, mais plus fortes. Nous suggérons que ce complexe de zebra soit inclus dans le sous-genre Maylandia.
Qu'il faille aussi inclure Ps. livingstonii et Ps. lombardoi, dépend de la valeur que l'on accorde au patron mélanique. Ps. lanisticola possède aussi six barres, mais ses dents pharyngiennes sont peu nombreuses et peu serrées.

For its validity we have to apply the 2nd edition of the Code as that was active at the time of publication (1984) but we may use additional rules of the 3rd edition to help save it because the first time the name Maylandia was contested was by Stauffer et al. in 1997. Since the name Maylandia was proposed as a subgenus we have the following two requirements to make it valid:

  1. (Article 13b): Genus-group names. -Every new genus-group name ...must... be accompanied by the fixation of a type species.
  2. (Article 13a): Requirements. -To be available, every new scientific name published after 1930 must satisfy the provisions of Article 11 [correct orthography], and must be (i) accompanied by a description or definition that states in words [not deducted from the text] characters that are purported to differentiate the taxon.

As we can see requirement number 1 has been met: the authors assigned greshakei as the type species of their new subgenus. However, requirement number two wants somewhere in the text a line such as "the subgenus Maylandia differentiates from the subgenus Pseudotropheus in the following characters, x, y, and z." If you describe a subgenus for the first time you automatically create two subgenera because the type of the genus becomes automatically the type of the nominal subgenus. In the case of Pseudotropheus (Maylandia) you automatically create Pseudotropheus (Pseudotropheus). Now it happens that in the same issue of the magazine the subgenus Maylandia was proposed, the subgenus Tropheops was described by Trewavas. Although we are certain that the authors knew about this description and they would have needed to differentiate their Maylandia also from Tropheops, it does not play a big role here as their description fails to comply with Code requirement Article 13a: there is no sentence that states in words the difference between Maylandia and the subgenus Pseudotropheus or the difference between Maylandia and all other (sub)genera. There is a section in which characters of a single species, P. williamsi, are mentioned but none that gives characters of Maylandia. Logically this automatically invalidates Maylandia because subsequent authors do not know what characters to look for to decide to place a species in Maylandia.

It can be deducted from the text (and even this is not stated!) that P. williamsi differs from Maylandia by the lack of vertical bars but this is not automatically a character that differentiates Maylandia from the subgenus Pseudotropheus. The genus Pseudotropheus never was a monotypic genus, which means that it always included more than one species. Furthermore the authors did not mention that the subgenus Pseudotropheus should be regarded monotypic. You cannot compare a (sub)genus with a single species to begin with and secondly the differentiating characters of the new subgenus have to be stated in words explicitly, and in this case those characters may not even include vertical bars for all we know.

Metriaclima greshakei A male of Pseudotropheus williamsi, type species of Pseudotropheus, at Chizumulu, {ake Malawi. Photo by Ad Konings.

Normally a good ichthyologist has no problems publishing a valid species description, but the authors of Maylandia, Meyer and Foerster, made a mess of their publication and we are doing them a favor in trying to rescue their proposed name. The authors themselves have not yet contributed to the discussion! In 1999 Condé and Gery published a paper in favor of the name Maylandia and brought forward two arguments. One of their arguments claims that the character(s) differentiating Maylandia is the fact that Maylandia has vertical bars. We may assume this easily but, as you can read for yourself in the "description", that was definitively not stated in words in the original paper. As mentioned above this was only mentioned as something P. williamsi does not have, but it was certainly not stated in words as a differentiating character of the subgenus Maylandia. As a note we should remember that the Code is not restricting the differentiating characters to sensible arguments. If the authors would have added a sentence such as: "Maylandia is distinguished from Pseudotropheus by the fact that its members leap out of the water onto the dry sand of the beach to lay their eggs" we all would know that this is nonsense but according to the rules we would have had a valid name! Of course, since we don't know any cichlid that behaves like that, no species could be placed into such a (sub)genus.

The second argument of Condé and Gery concerns so-called "combined descriptions". This is a rule (13c) in the Code that when you describe a monotypic genus you have to mention that the genus is monotypic and the characters given for either the species or the genus applies to both. This has been misinterpreted in several ways: first of all when Maylandia was proposed in 1984 this rule simply did not exist (it was introduced in the third edition (active from 1986) of the Code) so it is impossible for the authors to have thought of describing Maylandia with just the description of greshakei, its type species. However, when the name Maylandia was first contested (in 1997) the third edition of the Code was in effect so we can apply additional rules to save the name. Unfortunately for all proponents of Maylandia, this rule only applied to the description of genera, not subgenera. So, alas, no rescue from the third edition of the Code. In the latest edition of the Code (1999) this rule also applies to subgenera but that came into effect after the name Maylandia was pronounced a nomen nudum. In any respect, in order to apply the rule of "combined description" you need to mention explicitly that the new genus is monotypic. There needs to be a sentence such as: "Pseudotropheus (Maylandia) greshakei sp. n. gen. n." This the authors did not do as you can read in their text above. Moreover the authors suggested to include at least 6 other members of Pseudotropheus in their Maylandia which makes it hard to believe that the subgenus was thought to be monotypic. So the argument of Condé and Gery that Article 13c (combined description) alone is enough to validate the name Maylandia is incorrect.

I hope you understand now that it is not me or Stauffer et al. that decided that Maylandia is a nomen nudum and therefore invalid, but the rules of the Code. In 1997 Stauffer et al. gave a valid description of a new genus, Metriaclima, which includes all the species of the so-called P. zebra complex. In nomenclatural viewpoint this is the first time a name for this group has been correctly described and if you agree to the standpoint that the P. zebra complex ought to be in its own genus you should use Metriaclima for that genus, not Maylandia. If you do not think that the zebra complex needs to be separated from the other species in Pseudotropheus you will be perfectly correct referring to the zebra as Pseudotropheus zebra. You will be wrong referring to this species as Maylandia zebra, however.


Konings, Ad. (Jun 21, 2005). "Maylandia or Metriaclima, ...again!". Cichlid Room Companion. Retrieved on Dec 10, 2023, from: