{Cordylancistrus, Chaetostoma} platyrhynch{us,a}

[MatsP]

We appear to have

Cordylancistrus platyrhynchus

(Fowler, 1943) and Chaetostoma platyrhynchus (Fowler, 1943) [should that not be Platyrhyncha?] in the Cat-eLog. CoF and Fishbase says that Cordylancistrus platyrhynchus is the correct species name.

--
Mats

[Acanthicus]

Hi,

CoF and Fishbase says that Cordylancistrus platyrhynchus is the correct species name.

it is! Chaetostoma might sometimes look alike, but there are some differences which make it easy to clarify the genus.

[MatsP]

Well, obviously, we do have an explanatory text saying that Jon Armbruster moved this species some time ago. But my point is that we should have only ONE species, not two!

--
Mats

[Acanthicus]

If I got the point right I would just delete the Chaetostoma platyrhynchus and you end up with one/the right species.

[MatsP]

If I got the point right I would just delete the Chaetostoma platyrhynchus and you end up with one/the right species.

Indeed. I put a post here, because I can't delete the species, a) because I'm supposed to do work here at work, and b) there is actually not "delete a species" - you need to change the species into another one - which means I have to find a new species to add in as well.

--
Mats

[Marc van Arc]

Chaetostoma platyrhynchus/-a is an unknown species in both FB & CoF.

Chaetostoma platyrhynchus/-a is no synonym of Cordylancistrus platyrhynchus.

I've added the 2 synonyms (Hemiancistrus & Peckoltia) to the Cord. platyrhynchus data sheet.

[MatsP]

Yes, so we are following Armbruster personally in preference to CoF and Fishbase. And I suspect I added the second species because I didn't realize it was a PC special.

--
Mats

[Suckermouth]

Jon recognizes it as Chaetostoma platyrhyncha, and we will do so in an upcoming publication. Provenzano tentatively moved it back to Cordylancistrus so he's the most recent publication on it besides a simple taxonomic listing like Ferraris. Cordylancistrus is not monophyletic with recognition of Cordylancistrus platyrhynchus as a Cordylancistrus; it shares a few synapomorphies with Chaetostoma, but is distinguished from the rest of the members of the genus of course by the presence of snout plates, which of course is the definition of Cordylancistrus. Snout plate evolution gain and loss is homoplasious in the family (as shown by Paulasquama, Soromonichthys, and Chaetostoma).

Furthermore, this is another example of Ferraris/CoF ignoring Armbruster 2004.

[Jools]

So, shall I nuke the Cordylancistrus?

Jools

[MatsP]

Depends on who you listen to. CoF & Fishbase says Cordyalancistrus, as does Daniel above, where Milton and Armbruster wants Cheatostoma.

Whichever we keep, we probably need to move the pictures around...

--
Mats

[MatsP]

Ok, I'm merging the pictures into the Cordylancistrus (because it's got slightly better data). We can change the genus as we decide later.

I will then change the Chaetostoma into a new Peckoltia "Rio San Julian" that I've received a couple of pictures of.

Neither species has any registered keepers, so it's only Synonyms and Occurrences to worry about.

--
Mats

[MatsP]

So, I think what remains here is to decide what species name we should use.

By the way, I checked Armbruster's web-pages, and he uses Chaetostoma platyrhynchus, not -rhyncha!

--
Mats

[Suckermouth]

By the way, I checked Armbruster's web-pages, and he uses Chaetostoma platyrhynchus, not -rhyncha!

--
Mats

Hmmm, I'd go by his publication rather than his website.

[bekateen]

Ok, I'm merging the pictures into the Cordylancistrus (because it's got slightly better data). We can change the genus as we decide later.

I will then change the Chaetostoma into a new Peckoltia "Rio San Julian" that I've received a couple of pictures of.

@MatsP, @Acanthicus, and @Suckermouth: Hi All,

After reading this forum thread, I see that there were two separate issues here:

• One was the generic placement: Should this be
  Chaetostoma
  or
  Cordylancistrus
  ?
• The second was the specific epithet: Is it platyrhyncha? platyrhynchus? Or are there two species, one with the former epithet and one with the latter?

I want to share with you this excerpt from the recent Ballen et al. (2016) paper describing

Chaetostoma joropo

:

The correct spelling of Hemiancistrus platyrhynchus Fowler. Hemiancistrus platyrhynchus Fowler, 1943 is a species described from the Andean foothills of the upper Caquetá River basin in Colombia. It remained in its original genus until its relocation to Peckoltia by Isbrücker (1980). The first time it was associated with a genus of the Chaetostoma group was by Burgess & Finley (1996) following an unpublished meeting abstract by Provenzano & Milani, who relocated it to Cordylancistrus without further comments. Isbrücker (2001) kept the species in the latter genus, and after becoming a standard in loricariid classification the species was considered Cordylancistrus platyrhynchus. Armbruster (2004) relocated it to Chaetostoma based on his strict-consensus tree where this species is located at the base of the genus and in order to correct the non-monophyly of Cordylancistrus. The combination Chaetostoma platyrhynchus has been quite stable in taxonomic literature regarding the Chaetostoma group except for corrections in the spelling of the specific epithet. An ambiguity in the usage of the name platyrhynchus started with Armbruster (2004) who used indistinctly the names Chaetostoma platyrhynchus and Chaetostoma platyrhyncha for the same species in different sections of his article (e.g., pp. 45 and 72 for the former, and pp. 13, 34, 44 and 65 for the latter). Subsequently the same species was referred to as Chaetostoma platyrhynchus by the same author in a reanalysis of the phylogenetic relationships of the Loricariidae (Armbruster 2008), an action followed by Ballen & Vari (2012) and Ballen (2011). Finally, in the description of Cordylancistrus santarosensis, Tan & Armbruster (2012) used the name Chaetostoma platyrhyncha consistently throughout their paper, maintaining a dual usage of specific names for the same biological entity.

The fourth edition of the International Code of Zoological Nomenclature indicates that the gender in specific epithet must fit that of the genus except in very precise cases (Art. 34). It seems that the change in spelling introduced by Armbruster (2004) and followed by Tan & Armbruster (2012) was thought to follow this general rule of agreement in gender between genus and species (Art. 31.2); however, that being the case the combination should have been platyrhynchum (neuter) and not platyrhyncha (feminine), since Chaetostoma is neuter in gender. However, even gender coordination does not apply here following Art. 31.2.1 since platyrhynchus is a compound noun (from platys and rhynchos, both greek but latinized by Fowler as platyrhynchus in accordance with the original genus Hemiancistrus being masculine), and therefore it is to be treated as a noun in apposition with unchanged ending. Therefore, regardless of the generic combination (i.e., Chaetostoma or Cordylancistrus), its ending must be preserved from the original usage, and therefore the name has to be used as Chaetostoma platyrhynchus (Fowler).

So according to this paper, the second issue should be resolved straight-forward, and more recent works (subsequent to the most recent (2011) post in this thread) are still putting platyrhynchus in Chaetostoma. So how do we handle that? I’ll leave that for you to decide.

Cheers, Eric

[Jools]

This is now resolved, thanks all!

Jools