Hypostominae classification

[Silurus]

Armbruster JW & NK Lujan NK, 2024. New tribe-level classification of Hypostominae (Loricariidae) based on optimization of morphological states on DNA-based relationships, with descriptions of three new tribes and two new genera. Neotropical Ichthyology 22:e240108.

Abstract

Hypostominae tribe-level taxonomy is revised with new recognition and cladistic diagnoses of previously proposed family-level names for the Acanthicus (Acanthicini), Chaetostoma (Chaetostomatini), and Hemiancistrus (Spectracanthicini) clades. Three new tribes are described for the Peckoltia, Pseudancistrus,and ‘Pseudancistrus’ clades, with a new tribe erected for two new monotypic genera containing the sister species ‘Pseudancistrus’ sidereus and ‘P.’ pectegenitor. This third new tribe is known only from the upper Orinoco and Negro Rivers and is identifiable by having an accentuated keel on the caudal peduncle formed by dorsal laminae of the ventral plate series being strongly concave. The new genera are distinguishable by ‘P.’ pectegenitor having extremely long cheek odontodes reaching to the third plate of midventral plate series (vs. anterior to opercular opening in ‘P.’ sidereus) and 10 (vs. 7) branched dorsal-fin rays. We re-optimized morphological character-state change by mapping states previously used to infer evolutionary history onto a composite phylogenetic tree inferred from DNA-sequence data. This revealed the strong influence on morphology-based phylogenies of a correlated suite of opercular character states related to the mechanism for cheek odontode eversion. These states appear to be plesiomorphic within Hypostominae and to have been independently lost or reduced multiple times.

[Jools]

Great, thanks. Wait, when did the genera Colossimystax and Stellantia get described - what did I miss?

Cheers,

Jools

[Shane]

In the above paper. One sp was moved to each of the two new genera.
Colossimystax

Pseudancistrus pectegenitor

And
Stellantia

Pseudancistrus sidereus

-Shane

[bekateen]

I've created both genera and moved the two species.

• Colossimystax pectegenitor
• Stellantia siderea

Cheers,
Eric

[Jools]

In the above paper. One sp was moved to each of the two new genera.
Colossimystax

Pseudancistrus pectegenitor

And
Stellantia

Pseudancistrus sidereus

-Shane

Yes, sorry, I should actually read it properly! This then casts the spotlight on three l-numbers.

L122

which we'd want to be sure isn't a

Colossimystax

and

L439

,

L440

and

L491

aren't

Stellantia

. That initial selection is purely geographical. However, I am not following the dorsal lamina description, fig 2 attached.

The Dorsal Lamina (DL) appears to point to ventral plates or lamina? I've drawn red lines on a snip of fig 2 (below) to see if I have got even close to understanding what is being described in terms of the caudal peduncle (ish) plates being concave or not.

Comparative diagnosis. Stellantia is readily identified from all other Hypostominae except Colossimystax by having the dorsal lamina of each ventral plate of the caudal peduncle concave, accentuating the caudal peduncle keel (vs. caudal peduncle ventral plates rounded, lacking concave dorsal lamina, caudal peduncle keel weak or absent); and from Colossimystax by having seven branched dorsal-fin rays (vs. 10).

[bekateen]

Hi Jools,

I'm trying to understand the same thing. As I understand the concave dorsal laminae, I think it's best visible in figure C above and also in the photo from the original description of the species. That said, I don't know how it's identified in Fig A if it's not developed... Probably something I should know going forward (LOL).

Cheers, Eric