Megalosciades, Marceniuk & Oliveira & Ferraris Jr, 2024

Marceniuk, Alexandre Pires, Oliveira, Claudio & Ferraris Jr, Carl J., 2024, A new classification of the family Ariidae (Osteichthyes: Ostariophysi: Siluriformes) based on combined analyses of morphological and molecular data, Zoological Journal of the Linnean Society 200 (2), pp. 426-476 : 468-469

Megalosciades gen. nov.

( Figs 1–3 , 45 )

ZooBank registration: urn:lsid:zoobank.org:act:1DF58A15-AE63-4686-BEE0-9511F9971FFF .

Type species: Arius augustus Roberts, 1978 .

Diagnosis

The genus Megalosciades is defined based on unique characters of external morphology reported by Roberts (1978) in the species description: extremely short maxillary barbel; very small eye; broad head and broad mouth.

Etymology

Named for the disproportionally large head of the type species in comparison to those observed in Sciades and close relatives. Gender: masculine.

Included species

Megalosciades augustus Roberts, 1978 .

Habitat and distribution: Freshwater, southern New Guinea ( Fig. 38 ).

Remarks

Over that past two decades, Megalosciades augustus has been treated by different authors as a valid species in three different genera: Arius , Nemapteryx , and Neoarius . Molecular data (Betancur-R. 2009) does not support the inclusion of that species within any of those genera, nor does it appear to be the sister group of any of them. Although BI and ML analyses support the inclusion of Megalosciades augustus in Cochlefelis , the two genera are externally very distinct ( Figs 45 , 53 ) and the absence of internal morphological data makes it impossible to establish a diagnosis. This is an unstable situation, which may be resolved by assigning that enigmatic species to its own genus, within which it can remain until a discoverery that its phylogenetic position is actually embedded within another genus.

Figures

Figure 1. MP analysis.Subfamilies (SF) Galeichthyinae (pink), Bagreinae (bright blue), and Ariinae (dark blue). Tribe (T) Ariini (blue), Cathopsini (orange), Genidentini tribe nov. (brown), and Sciadeini tribe nov. (light green).Subtribe (ST) Ariina (light blue) and Doiichthyina (green). Incertae sedis taxa (IS) (red). Numbers over branches correspond to the bootstrap support.

Figure 2. ML analysis. Subfamilies (SF) Galeichthyinae (pink), Bagreinae (bright blue), and Ariinae (dark blue). Tribe (T) Ariini (blue), Cathopsini (orange), Genidentini tribe nov. (brown), and Sciadeini tribe nov. (light green). Subtribe (ST) Ariina (light blue) and Doiichthyina (green). Incertae sedis taxa (IS) (red). Numbers over branches correspond to the bootstrap support.

Figure 3. BI analysis.Subfamilies (SF) Galeichthyinae (pink), Bagreinae (bright blue), and Ariinae (dark blue). Tribe (T) Ariini (blue), Cathopsini (orange), Genidentini tribe nov. (brown), and Sciadeini tribe nov. (light green).Subtribe (ST) Ariina (light blue) and Doiichthyina (green). Incertae sedis taxa (IS) (red). Numbers over branches correspond to the bootstrap support.

Figure 38. Representative skulls, in dorsal view, and distribution of the subtribe Doiichthyina.A, Brustiarius nox, AUM 47488. B, Paracinetodus carinatus, AUM 47550.C, Cochlefelis spatula, AUM 50296. D, Nedystoma dayi, AUM 47500. E, Aceroichthys dioctes, AUM 47507. F, Pachyula crassilabris, AUM 47509. G, Pararius proximus, AUM 47486.H, Potamosilurus velutinus, AUM 47489.* marine, ** brackish waters, *** freshwater.

Figure 45. Megalosciades augustus Roberts, 1978, Papua New Guinea, photograph by Ricardo Betancur-R., type species of the genus.

Figure 53. Potamosilurus macrorhynchus, ZMA 111086, New Guinea, type species of the genus.