Austrolebias Costa, 1998

Alonso, Felipe, Terán, Guillermo Enrique, Alanís, Wilson Sebastián Serra, Calviño, Pablo, Montes, Martin Miguel, García, Ignacio Daniel, Barneche, Jorge Adrián, Almirón, Adriana, Ciotek, Liliana, Giorgis, Pablo & Cascioưa, Jorge, 2023, From the mud to the tree: phylogeny of Austrolebias killifishes, new generic structure and description of a new species (Cyprinodontiformes: Rivulidae), Zoological Journal of the Linnean Society 199 (1), pp. 280-309 : 288-289

Genus Austrolebias Costa, 1998

Type species: Cynolebias bellottii Steindachner, 1881 , type by original designation.

Diagnosis: Genus Austrolebias can be distinguished from other genera within the Austrolebias genus group by the following unique combination of characters: (1) urogenital papillae attached to anal fin (except in Austrolebias vandenbergi and Austrolebias accorsii ); (2) anteromedial anal fin rays longer than the rest in females, resulting in a nearly triangular fin shape; (3) males pectoral fins hyaline, with black margin and iridescent submargin (except Austrolebias melanoorus , which has only the black margin); (4) pelvic bones overlapping; (5) absence of regular, well-defined vertical dark grey bars only on anterior portion of flank (anterior to the anal fin origin); (6) absence of dark grey pigmentation in cephalic neuromasts concentrated in parietal series; and (7) in females, absence of black spots on posterior flank and vertically aligned in the peduncle.

Differential diagnosis: The genus Austrolebias 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 being hyaline in adult males (vs. non-hyaline in Argolebias , Acantholebias , Matilebias , Megalebias , Acrolebias and Cypholebias ); anteromedial anal fin rays longer than the rest of the fin rays in females, resulting in a nearly triangular fin shape (vs. rounded anal fin in Amatolebias ); urogenital papillae attached to male anal fin, if not, presence of contact organs on anal fin (vs. urogenital papillae not attached to male anal fin in all Garcialebias species except Garcialebias cheffei Volcan et al., 2021 , which differs from Austrolebias by the lack of contact organs on the anal fin).

Synapomorphies: Austrolebias genus s.s., as defined herein, was recovered as monophyletic with the current species composition and supported by 24 molecular synapomorphies and the following four morphological synapomorphies (see Supporting Information, Appendix S5): dark grey to black spots on flanks of males (21:1); female anal fin roughly spatula-shaped (50:1); pelvic fins membrane in males fused along most of medial margin (58:1); and pelvic bones overlapping (190:1).

Included species: Austrolebias melanoorus (Amato, 1986) , Austrolebias vandenbergi (Huber, 1995) , Austrolebias univentripinnis Costa & Cheffe, 2005 , Austrolebias queguay Serra & Loureiro, 2018 , Austrolebias bellottii (Steindachner, 1881) , Austrolebias accorsii Nielsen & Pillet, 2015 and Austrolebias ephemerus Volcan & Severo-Neto, 2019 .

Remarks: According to the Eschmeyer’s Catalogue of Fishes ( Fricke et al. 2021), Austrolebias vandenbergi should be corrected to vandenbergorum following ICZN Art. 31.1.2 because this species was originally described in honour of Leen van den Berg and his son Arjen. We consider this not to be adequate because vandenbergi has been in use for> 25 years and cited in ≥ 20 papers ( Fricke et al. 2021) and, following Appendix B General recommendations of the ICZN ( Ride et al. 1999): ‘Stability of nomenclature: 1. Since it is the object of nomenclature to denote each taxon by a name which is unique, unambiguous and universal, an author should not change the prevailing usage of names, or the sense in which they are used, unless this is required for scientific reasons (i.e. the reclassification of taxa) (…) 2. If the provisions of the Code appear to require an action which might threaten stability or cause confusion, that action should not be taken before referring the case to the Commission for advice’. Therefore, until this is submitted to the Commission, we consider that vandenbergi should be used for stability.

Distribution: Río de la Plata basin (excluding the middle and upper Paraná and Uruguay river basins), Laguna Merín basin and headwaters of the Mamoré basin, in Argentina, Uruguay, Brazil, Bolivia and Paraguay.