History:

1876: Steindachner F. describes the genus Cynolebias. Type-species: by monotypy as Cynolebias porosus Steindachner, 1876.

Cynolebias refers to the "dog-like" form of the conical teeth that are characteristic of this genus. 

1998; Costa W. splits Cynolebias into 3 genera i.e., Cynolebias, Austrolebias. (Type-species: by original designation as Cynolebias bellottii Steindachner, 1881.) and Megalebias (Type-species: by original designation as Cynolebias wolterstorffi Ahl, 1924).

The name Austrolebias refers to the members of the group living in the southern part of South America, in the southern states of Brazil, in Paraguay, Uruguay and the northern part of Argentina. In winter, these areas can become very cool. The fishes live in temporarily inundated places and stagnant pools, always near rivers. Up to five species may be sympatric (live together). Because of their isolation, each species can develop diverse color varieties. This has lead to some confusion as to whether neighboring populations are distinct species, or simple color variants.

2006: Costa W., synonimizes Megalebias with Austrolebias.

2008: Costa W., erects 6 new subgenera in Austrolebias i.e., Acantholebias, (Type-species: by original designation (also monotypic) as Cynolebias luteoflammulatus Vaz-Ferreira, Sierra & Paulette, 1964.); Acrolebias, (Type-species: by original designation as Cynolebias carvalhoi Myers,1947.); Austrolebias, Type-species: by original designation as Cynolebias bellottii Steindachner, 1881.); Argolebias, (Type-species: by original designation as Cynolebias nigripinnis Regan, 1912.); Cypholebias, (Type-species: by original designation as Cynolebias robustus Günther, 1883.); Gymnolebias, (Type-species: by original designation as Cynolebias gymnoventris Amato, 1986); and redifines the former Megalebias as the 7th subgenus in Austrolebias. (Type-species: by original designation as Cynolebias wolterstorffi Ahl, 1924).

2018: Lanes et al. came with a molecular and morpho-combined full revision of Austrolebias, with major reshuffling, and proposed 2 unnamed subgenra to be added to the already 7 excisting subgenera, but without proper diagnoses.

2023: Alonso et. al., up-levels all 7 sub genera into genus status, changes the position of several species in the existing sub genera and add 4 new genera to the then 7 genera making 11 genera in total. His team makes work from the diagnoses and provide a key to make the basic differences between the new genera clear. They explain this move as being possible subjective, but give their reasons to to so. Thus, with this work, Austrolebias is now divided into 11 genera, i.e., Acantholebias, Acrolebias, Argolebias, Amatolebias (new gen.), Austrolebias, Garcialebias (new. gen), Gymnolebias, Cypholebias, Megalebias, Matilebias (new gen.), Titanolebias (new gen.)

Above table showing the history on how the genus Austrolebias was established. The table is taken from the paper by Alonso et. al, in 2023.

Genus Austrolebias Costa, 1998

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

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.

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).

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.

Argumentation cited from the Alonso et al. 2023 paper:

The decision to elevate the sub genera of the former genus Austrolebias to genus status is subjective. Although the genus s.l. is still monophyletic, an alternative decision could have been made to redefine these clades as sub genera, in order to prioritize taxonomic stability. However, differentiating these groups of species into strongly defined and differentiated groups of genera based on morphological and molecular evidence aligns with the prevailing taxonomy in Rivulidae. This approach facilitates the study of their biological characteristics in various fields, including behavior, physiology, anatomy, molecular biology, development and genetics. It also provides a context for scientists to discuss and study different organisms and for the public to learn and become familiar with species and their biology. Furthermore, a nomenclature that reflects biological gaps and identifies relatively homogeneous groups is useful for any purpose beyond the desired stability of the nomenclature. Taxonomy is a fundamental auxiliary discipline that helps us to organize, use and understand biological diversity, and we should consider its usages and implications.

Therefore, elevating the said sub genera to genus status is the best decision, because it allows for the recognition of groups that are notably different from each other but have broad similarities within them. This approach also recognizes the evolutionary divergence and diversity of other Rivulidae-related genera, making them more comparable biological units, and contributes to development of conservation and management policies. In this line, the case of Rachovia Myers, 1927 and Austrofundulus Myers, 1932 is a good example. Hrbek et al. (2005) justify the validity of those genera, stating that ‘it is generally agreed that generic designations should encompass not only monophyletic units, but also a morphologically and ecologically distinct groups, thus conveying additional information above and beyond the species level’. A similar approach was followed by Freyhof & Yoğurtçuoğlu (2020) for the generic structure of Aphaniidae or by Costa (1998a) when he erected Austrolebias and Megalebias for species previously placed in Cynolebias s.l., for which monophyly was not refuted. The present arrangement is therefore more in agreement with the morphological divergence and diversity of other Rivulidae-related genera, such as Spectrolebias, Cynolebias, Hypsolebias, Nematolebias, Sympsonichthys and Ophtalmolebias, making them more comparable units. Therefore, we decided that the best decision was to elevate the said subgenera to genus status. Finally, several new species of the Austrolebias genus group have been described in recent years (i.e. Alonso et al. 2018, Serra and Loureiro 2018, Volcan and Severo-Neto 2019, Lanés et al. 2021, Volcan et al. 2021), which emphasizes the importance of further investigation on seasonal killifishes in South America, because several species are probably undescribed while the conservation of those species is particularly threatened by agricultural expansion (e.g. Alonso et al. 2018, Tagliacollo et al. 2021), and many species might became extinct in the next decades. Additionally, although Uruguay and Brazil (e.g. ‘Sumário Executivo do Plano de Ação Nacional de Conservação de Peixes Rivulídeos Ameaçados de Extinção’) have some public policies and legislations in order to protect this group of species, there are none towards the conservation of seasonal killifish in other South American countries, such as Argentina, Paraguay and Bolivia, urging for an increase in the visibility of this particularly vulnerable group of fish to the general public and decision makers and the necessity to fund and promote research on this group. Also, there is an important requirement for conservation of the extremely fragile ephemeral wetlands, which house several endemic species and are being lost owing to human impacts, such as habitat modification and loss, climate change, contamination and the introduction of exotic species (i.e. Alonso et al. 2018, Campos et al. 2021, Pelicice et al. 2021, Tagliacollo et al. 2021).

Comment by sitemanager:

Regrettably, this path has been chosen, and that sub genera have been upgraded to genera, sometimes containing only a single or few species.

From a taxonomic point of view, it is subjective to do this as they themselves point out and confirm the monophyly of the genus Austrolebias. The description of the genera is in itself, according to the code of international nomenclature committee, correctly done. However, the reasons they give for overruling the, so far applied rules of taxonomy are weak, except perhaps the reason to better protect the species from extinction due to human intervention. But even that aspect can be included in the use of sub genera though it may be somewhat less weighty for policy makers. The other reasons are all based on feelings and some inaccuracies where the examples they give are from the past. For example, Costa did indeed divide Cynolebias into 3 different genera, dividing Cynolebias s.l. into Cynolebias, Austrolebias and Megalebias, but Megalebias was later synonymized with Austrolebias by Costa himself when it turned out that its position as a genus was taxonomically unsustainable. Then, in 2008, Megalebias became one of the 7 new sub genera of Austrolebias.

Hrbek et al., 2005 point out the following:

Costa (1990) synonymized Austrofundulus Myers 1932 with Rachovia Myers 1927, but in a later publication (Costa 1998) resurrected Austrofundulus as a separate genus without justification. We follow Taphorn and Thomerson (1978) in recognizing both genera. Although there are no universally accepted definitions as to what constitutes a genus, it is generally agreed that generic designations should encompass not only monophyletic units but also morphologically and ecologically distinct groups, thus conveying additional information above and beyond the species level. Since this analysis shows Austrofundulus species to be a monophyletic group, and Austrofundulus and Rachovia form morphologically distinct units (Taphorn and Thomerson 1978), the retention of Austrofundulus as a separate genus is justified.

This can be a way to create new genera. Still, if the multiple units consist of only one or two species and the differences are mainly based on minor differences in coloration, markings, genetic data, and morphology, it may be a better choice in my personal opinion, to use "subgenus" status instead, for all these morphologically distinct units because it evenly allows for the recognition of groups that are notably different from each other but have broad similarities within them. The frequent use of the terminology "Austrolebias genus group" in the paper evokes questions for the public and scientist because one should not taxonomically divide a monophyletic genus like Austrolebias into multiple genera but can clarify their differences by dividing the genus into sub genera. My question remains why reviewers did not intervene here, and I agree with J.H. Huber in Killi Data Whassup nr. 15, Killi Data Online. "The Pandora Box" is fully open now!

Literature:

Steindachner, F. 1876. Ichthyologische Beiträge (V). Sitz. Akad. Wiss. Wien mathem.-naturwiss. Klasse Abt.1, 74: 172.

Costa, W.J.E.M. 1998. Phylogeny and Classification of Rivulidae revisited: Origin and Evolution of Annualism and Miniaturization in Rivulid Fishes (Cyprinodontiformes: Aplocheilidei). J. Comp. Biol., 3 (1), December: 75.

Hrbek, T., D.C. Taphorn & J.E. Thomerson. 2005. Molecular Phylogeny of Austrofundulus Myers (Cyprinodontiformes: Rivulidae), with Revision of the Genus and the Description of four new species. Zootaxa, 825: 1-39, 16 figs., 9 tabs.

Costa, W.J.E.M. 2008. 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 bi-typic genus, with 6 other subgenera, Acantholebias (valid), Acrolebias, Austrolebias s.s., Gymnolebias, Cypholebias, Megalebias , 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.