Matilebias, Alonso & Terán & Alanís & Calviño & Montes & García & Barneche & Almirón & Ciotek & Giorgis & Cascioưa, 2023

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

Matilebias gen. nov.

LSID urn:lsid:zoobank.org:act:85736BEB-72A7-407E-B6A4-FF2C29FCECE9

Type species: Cynolebias alexandri Castello & López, 1974 .

Diagnosis: It can be distinguished from the remaining genera of the Austrolebias genus group by the following combination of characters: (1) grey pectoral fin without iridescent spots on medial distal portion; (2) absence of a gap between the preopercular and mandibular series of neuromasts; (3) border of most scales on dorsal half of flank, below dorsal fin, in dominant mature males (not considering bands, bars and iridescent lines) light grey to brownish grey; (4) one or more irregularly arranged black spots on the posterior portion of the flank and caudal peduncle in females; (5) vertically aligned iridescent markings on entire flank; and (6) one or two gill rakers on epibranchial 1.

Differential diagnosis: The genus Matilebias 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, vertically directed subocular bar and pelvic fins without an obvious interspace in males (vs. posteriorly directed subocular bar, anterior region of head near rostral neuromasts without scales and conspicuous interspace between pelvic fins in males of Megalebias ); by marks on dorsal fin distal portion, if present, not fused (vs. present and fused in Argolebias ); by lack of contact organs in the anal fin of males (vs. present in Cypholebias ); and by unpaired fins with bluish to greenish iridescences on males (vs. dark grey in Acrolebias ).

Synapomorphies: Matilebias is a monophyletic clade supported by 54 molecular synapomorphies and by one morphological synapomorphy (see Supporting Information, Appendix S5): one or two gill rakers in epibranchial 1 (154:1)

Includedspecies: Matilebiaslitzi Costa, 2006 comb.nov., Matilebias cyaneus Amato, 1986 comb. nov., Matilebias paucisquama Ferrer et al., 2008 comb. nov., Matilebias toba Calviño, 2006 comb. nov., Matilebias alexandri Castello & López, 1974 comb. nov., Matilebias ibicuiensis Costa, 1999 comb. nov., Matilebias periodicus Costa, 1999 comb. nov., Matilebias duraznensis García, Scvortzoff & Hernández, 1995 comb. nov., Matilebias juanlangi Costa et al., 2006 comb. nov., Matilebias affinis Amato, 1986 comb. nov. and Matilebias camaquensis Volcan et al., 2017 comb. nov.

Etymology: Genus dedicated to the memory of the late Dr Matias Pandolfi, for his contributions to the ichthyological knowledge of fish physiology and his commitment to the popularization of science, human resource training and public education in the sciences. Composed of his nickname, ‘Mati’, and from the Greek lebias (small fish, a name commonly used to compose generic names of cyprinodontiform fishes).

Distribution: Lower basins of the Paraguay and Paraná rivers, middle and lower basin of the Uruguay River and Patos-Merín lagoon system in Uruguay, Brazil and Argentina.