Trematochromis or Ctenochromis benthicola?

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Rico Morgenstern
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Trematochromis or Ctenochromis benthicola?

Post by Rico Morgenstern » Sun Jun 22, 2008 4:18 am

May be this problem has been allready discussed anywhere in this forum, but I would bring it up again, for I tried to get some deeper insights into the Central African haplochromines. Unfortunately I don't have seen Max Poll's paper from 1986, in which benthicola was placed in Ctenochromis so I don't know the exact reasoning for doing so. According to the diagnosis of Ctenochromis by Greenwood (1979), the species in my opinion cannot be included in Ctenochromis since it shows none of the diagnostic squamation characters (reduced cheek squamation, nacked patches on the chest, position of upper lateral line relative to the dorsal fin base) as well as a very different dentition. I would add, that in general appearance (shape, color pattern, etc.) this species differs strikingly from all other Ctenochromis including C. horei from L. Tanganyika, as well as from all other Haplochromines in the widest sense.

We have a diagnosis which excludes benthicola from Ctenochromis, we have also a phyletic study which places the species even in a new tribe (Takahashi, T.: Systematics of Tanganyikan cichlid fishes[Teleostei, Perciformes]. Ichthyological Research 2003: 367-382), and we have even the alternative generic name Trematochromis Poll, 1987, so why should the species not be referred to as Trematochromis benthicola? What do you think?

Best regards!
RM

Mark Smith
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Re: Trematochromis or Ctenochromis benthicola?

Post by Mark Smith » Sun Jun 22, 2008 9:32 am

I am inclined to refer to it as Ctenochromis in quotes ("Ctenochromis") for the time being, since that is the most recently generic assignment formally presented in a scientific paper, and with the quotes to indicate the placment in this genus is most likely tentative. More recently, it seems apparent to us now that it should be removed from that genus and placed into another, possibly newly created one. Therefore, it would be great to see someone publish a formal paper re-assigning it to it's own unique genus, thereby putting an end to it's current nebulous generic placement. As to whether it should be transferred to the genus Trematochromis, hard to say, as this genus name is no longer valid. Perhaps someone more familiar with the rules of nomenclature could shed more light on whether or not such a move would hold up to scrutiny.

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Re: Trematochromis or Ctenochromis benthicola?

Post by Philippe Burnel » Sun Jun 22, 2008 12:11 pm

Mark Smith wrote: As to whether it should be transferred to the genus Trematochromis, hard to say, as this genus name is no longer valid.
why not valid ?
It's describtion is valid ! and it's type species is a synonym of bethicola... so Trematochromis can be used for this species which needs a generic name.

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Re: Trematochromis or Ctenochromis benthicola?

Post by Alex Calder » Sun Jun 22, 2008 9:01 pm

The genus Trematochromis is still valid.

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Re: Trematochromis or Ctenochromis benthicola?

Post by Mark Smith » Sun Jun 22, 2008 9:07 pm

Why do you say this genus name is still valid?

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Re: Trematochromis or Ctenochromis benthicola?

Post by Philippe Burnel » Mon Jun 23, 2008 12:26 am

Mark Smith wrote:Why do you say this genus name is still valid?
Why couldn't it be valid ?

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Re: Trematochromis or Ctenochromis benthicola?

Post by Mark Smith » Mon Jun 23, 2008 8:33 am

Are you aware of this paper:

Trematochromis schreyeni Poll, 1987, a junior symonym of 'Ctenochromis' benthicola (Matthes, 1962)(Perciformes: Cichlidae) from Lake Tanganyika, in Journal of Fish Biology (2006) 68 (Supplement A), 56-67

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Re: Trematochromis or Ctenochromis benthicola?

Post by Alex Calder » Mon Jun 23, 2008 9:07 am

My mistake, here's a correction.

Trematochromis schreyeni is a junior synonym to Ctenochromis benthicola.
So by my understanding Trematochromis schreyeni is invalid it is more that Ctenochromis benthicola is proper.

Source:
Eschmeyer, W. N. Catalog of Fishes electronic version (updated 23/04/2008): http://www.calacademy.org/research/icht ... earch.html

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Re: Trematochromis or Ctenochromis benthicola?

Post by Philippe Burnel » Mon Jun 23, 2008 9:19 am

Mark Smith wrote:Are you aware of this paper:

Trematochromis schreyeni Poll, 1987, a junior symonym of 'Ctenochromis' benthicola (Matthes, 1962)(Perciformes: Cichlidae) from Lake Tanganyika, in Journal of Fish Biology (2006) 68 (Supplement A), 56-67
That's why Trematochromis can be used for benthicola !
Imagine that a guy describe a new genus for benthicola (which is not a Ctenochromis). Everybody will say that there is a genus previously described for this species and this genus is Trematochromis...
There is no reason to say that GENUS Trematochromis is not valid. There are only reasons to say that species shreyeni is synonym of benthicola

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Re: Trematochromis or Ctenochromis benthicola?

Post by Mark Smith » Mon Jun 23, 2008 9:29 am

Will the rules of zoological nomenclature accept this change of genus names without a formally published paper justifying/explaining it?

Does our declaration (here on Cichlidae.com) that Trematochromis is now the new genus name for benthicola, thereby make it valid/correct?

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Re: Trematochromis or Ctenochromis benthicola?

Post by Alex Calder » Mon Jun 23, 2008 6:25 pm

Mark Smith wrote:Will the rules of zoological nomenclature accept this change of genus names without a formally published paper justifying/explaining it?
I don' think so.
Does our declaration (here on Cichlidae.com) that Trematochromis is now the new genus name for benthicola, thereby make it valid/correct?
That would beget disaster.

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Re: Trematochromis or Ctenochromis benthicola?

Post by Mark Smith » Mon Jun 23, 2008 6:33 pm

Thank you Alex!

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Re: Trematochromis or Ctenochromis benthicola?

Post by Mike Wise » Wed Jun 25, 2008 11:37 am

Instead of saying the genus name Trematochromis is or is not valid, it might be better stated that it presently does not formally exist. The next question: is it available or is it a 'nomen nudem'??

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Re: Trematochromis or Ctenochromis benthicola?

Post by Darrell Ullisch » Wed Jun 25, 2008 12:08 pm

A "nomen nudum" is a name without a description; there is a good description for the genus name, therefore, it cannot be a nomen nudum. Asking whether or not it "formally exists" is the same as debating the validity.

There are incidents in the past where a genus was described on a species that turned out to be a previously described species in another genus. Usually the person who points this out also argues for/against using the new genus name, but this doesn't always happen. As Philippe has pointed out, Trematochromis isn't necessarily invalid; The question is, did the paper synonymizing the two species address the issue at all? If not, history says that one simply moves the old species into the new genus. Oddly, the type species is still schreyeni, but it has to now be noted as a junior synonym of benthicola.

This has happened in the past with the Killifish genus Aphyosemion. The type species of that genus is A. castaneum, which is a junior synonym for A. christyi. The genus is still valid, as that part of the description was viable.
There are two kinds of error: blind credulity and piecemeal criticism. Sound skepticism is the necessary condition for good discernment; but piecemeal criticism is an error. - Egyptian proverb

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Re: Trematochromis or Ctenochromis benthicola?

Post by Rico Morgenstern » Wed Jun 25, 2008 1:22 pm

Thank you all for your comments!
Darrell Ullisch wrote:The question is, did the paper synonymizing the two species address the issue at all? If not, history says that one simply moves the old species into the new genus. Oddly, the type species is still schreyeni, but it has to now be noted as a junior synonym of benthicola.
Yes the issue is discussed by Takahashi & al. (2006):
The correct generic allocation of ‘C.’ benthicola is still undecided (Takahashi, 2003a). The species was originally described as Haplochromis benthicola by Matthes (1962), and was placed in Ctenochromis Pfeffer, 1893 by Poll (1986). In subsequent literature, both genera have been used for this species (Haplochromis in Brichard, 1989 and Axelrod, 1996; Ctenochromis in Konings, 1988, 1998 and Takahashi, 2002b, 2003a, b). Takahashi (2003a) has noted that the generic allocation of C. benthicola could not be decided until a careful revision of the genus had been made with examination of the type species, Ctenochromis pectoralis Pfeffer, 1893. This is a complex taxonomic problem that should be addressed in another study. Until then, the convention used by Takahashi (2003a) was followed and the genus name Ctenochromis put between quotes, indicating the problems with the use of this genus name for this species.
The synonymy of T. schreyeni with ‘C.’ benthicola would suggest that Trematochromis is a junior synonym of the genus ‘Ctenochromis’, as defined by Poll (1986).
Certainly it would be the correct procedure to use a more conservative nomenclature for some reason, but I think there is a contradiction in treating the species benthicola as it were excluded from Ctenochromis (as indicated by putting the generic name in quotes in the papers of Takahashi 2003 as well as in Takahashi & al. 2006) and not using the next available name Trematochromis. Of course the use of quotation marks is not regulated by the code or elsewhere, however, as per tacit understanding they are used to indicate that the species in question does not belong to the genus to which it was previously placed, but it cannot be assigned to another nominal genus.

In my opinion there are only two possibilities (three if one takes the name Haplochromis into consideration) : Ctenochromis without quotes (if you accept the inclusion in that genus or even if you think that an exclusion is just not sufficiently substantiated) or Trematochromis (if you would state that the species doesn't belong to Ctenochromis). I would prefer the latter variant for the reasons stated in my initial post, but I am not an ichthyologist...

Best regards!
RM

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