Argolebias Costa, 2008 as a subgenus of Austrolebias

Type-species: by original designation as Cynolebias nigripinnis Regan, 1912.

Genus Argolebias Costa, 2008 stat. nov.

Species included: Argolebias nigripinnis Regan, 1912 comb. nov., Argolebias guarani sp. nov. and Argolebias paranaensis Costa, 2006 comb. nov.

Diagnosis:

The genus Argolebias can be distinguished from all other genera of the Austrolebias genus group by presenting iridescent spots on the medial distal portion of the pectoral fin and by the following unique combination of characters: (1) a gap between preopercular and mandibular series of neuromasts; (2) a wide dark grey to black border on most scales on the ventral half portion of the flank, above the anal fin, in mature dominant males (not considering bands); (3) fused iridescent marks on the distal portion of the dorsal fin; (4) black blotch on the most anterior region of the dorsal fin; (5) absence of dark grey to black spots on flanks in males; and (6) dorsal radial of pectoral fin absent.

Differential diagnosis: In addition to the unique combination of character states mentioned in the Diagnosis above, the genus Argolebias can be distinguished from all other genera of the Austrolebias genus group by having < 40 scales in the longitudinal series (vs. > 40 scales in Titanolebias); by the presence of scales in the preopercular region (vs. absent in Gymnolebias); by the basal and medial region of pectoral fins non-hyaline in adult males (vs. hyaline in Amatolebias, Austrolebias and Garcialebias); by the lack of ossified contact organs in the anal fin of males (vs. present in Acantholebias); by presenting the rostral region scaled, subocular bar vertically directed and pelvic fins without an obvious interspace in males (vs. subocular bar posteriorly directed, anterior region of head near rostral neuromasts without scales and conspicuous interspace between pelvic fins in males, in Megalebias); and by presenting longitudinally aligned and fused iridescent marks on the distal portion

of the dorsal fin (vs. if present, marks on dorsal fin distal portion not fused, in Acrolebias, Cypholebias and Matilebias). Synapomorphies: Argolebias is a monophyletic clade supported by one morphological synapomorphy (see Supporting Information, Appendix S5): dorsal radial of pectoral fin absent.

Distribution: Flood plains of the middle and lower Uruguay River, middle and lower Paraná basins and Río de la Plata estuary, in Argentina, Uruguay, Brazil and Paraguay.

Literature:

Regan, C.T. 1912. Revision of the Poeciliid Fishes of the Genera Rivulus, Pterolebias, and Cynolebias. Ann. & Mag. Nat. Hist., 8 (10): 508.

Catalog of aplocheiloid Killifishes of the World. Universidade Federal do Rio de Janeiro Ed., Rio de Janeiro, Brasil, 51.

Lanés, Volcan, Calviño, Nielsen, Duarte & Garcia, 2018 : molecular and morpho-combined full revision of Austrolebias, with major reshuffling of components into subgenera, with subgenus Argolebias as primitive to all and a probably distinct bitypic genus, with 6 other subgenera, Acantholebias (valid), Acrolebias (probably valid), Austrolebias s.s. (valid), Gymnolebias (unstable), Cypholebias (unstable), Megalebias (valid), conservatively maintained {without new diagnoses} and 2 un-named subgenera.

Alonso F., G.E. Terán, W.S. Serra Alanís, P. Calviño, M.M. Montes, I.D. Carcía, J.A. Barneche, A. Almirón, L. Ciotek, P. Giorgis, J. Casciotta, 2023. From the mud to the tree: phylogeny of Austrolebias killifishes, new generic structure and description of a new species (Cyprinodontiformes: Rivulidae) Zool. Journ. of the Linnean Society, XX, 1-30, Fig. 15, Tab. 2.

See: Austrolebias group introduction page for comment.