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 : 283-285

Genus group Austrolebias

This genus group is composed of the following genera: Argolebias stat. nov., Amatolebias gen. nov., Matilebias gen. nov., Austrolebias s.s., Gymnolebias stat. nov., Acantholebias stat. nov., Megalebias , Titanolebias gen. nov., Acrolebias stat. nov., Cypholebias stat. nov. and Garcialebias gen. nov.

Diagnosis: This group of genera can be distinguished from other genera of the family by presenting the following unique combination of characters (each of them not necessarily exclusive): (1) absence of scales in the suborbital region; (2) extension of the broad dorsal portion of the cleithrum, twice as high as the vertical distance between the dorsal margin of the scapula and the ventral margin of the coracoid; (3) a dark grey suborbital bar (faint and diffuse in Gymnolebias ); (4) a short extension of the ventral process of the angulo-articular, with retro-articular projecting slightly below the ventral process of the angulo-articular; (5) urogenital papillae close to the anal fin in males; and (6) anterior nostrils pointing dorsolaterally [reversed in Argolebias guarani , pointing ventrolaterally, and in Titanolebias cheradophilus Vaz-Ferreira, Sierra de Soriano & Scaglia de Paulete 1965, pointing forwards].

Additional characters useful to identify members of this group: (7) urohyal high (reversed to stylized in Titanolebias , except T. cheradophilus ); (8) dark grey dashed bars or spots on flanks of females (reversed to spots in Acantholebias ); (9) 10–13 pectoral fin rays (reversed to 12–15 in Megalebias ); (10) cartilage proportion of basihyal 45–70% [reversed> 70% in Austrolebias vandenbergi and <45% in Acantholebias , Gymnolebias , T. cheradophilus and Titanolebias elongatus (Steindachner, 1881) ]; (11) absence of filaments on dorsal fin; (12) distal margin of anal fin rounded in males; (13) deep blue iridescent coloration of the opercular region (reversed to pale greenish gold in Megalebias , Cypholebias , Austrolebias vandenbergi , Acrolebias carvalhoi and Ga. araucarianus ); and (14) absence of scales in the basal portion of the anal fin in males (reversed to present in Titanolebias prognathus Amato, 1986 , Titanolebias monstrosus Huber, 1995 , T. elongatus , Austrolebias vandenbergi and Austrolebias accorsii ).

Differential diagnosis: The Austrolebias genus group can be differentiated from other genera of the Rivulidae family outside this group as follows:

1. Posterior distal margin of the dorsal fin in males rounded (vs. pointed in Gnatholebias , Micromoema , Pterolebias , Pituna , Maratecoara , Mucurilebias , Notholebias , Leptopanchax , Leptolebias , Campellolebias , Cynopoecilus , Xenurolebias , Nematolebias , Ophthalmolebias and Simpsonichthys ) ( Garman 1895, Thomerson 1974, Costa 1988, 1995b, 2002, 2006c, 2007a, 2007b, 2009, 2011, 2012, 2016b, Thomerson and Taphorn 1992, Costa and Amorim 2014, Costa et al. 2014a, 2016, Ferrer et al. 2014, Nielsen et al. 2017).

2. Between 17 and 28 dorsal fin rays in males (vs. <17 in Kryptolebias , Atlantirivulus , Anablepsoides , Rivulus , Prorivulus , Cynodonichthys , Melanorivulus , Laimosemion , Millerichthys , Moema , Trigonectes , Neofundulus , Rachovia , Terranatos , Renova , Papiliolebias , Stenolebias and Plesiolebias ) ( Weitzman and Wourms 1967, Miller and Hubbs 1974, Taphorn and Thomerson 1978, Costa 1989, 1990, 1993, 1995b, 2003a, 2003b, 2004a, 2004b, 2005, 2006b, 2007b, 2008a, 2015, 2017b; Thomerson and Taphorn 1995, Vermeulen and Hrbek 2005, Costa et al. 2013, Nielsen and Brousseau 2014, Valdesalici and Brousseau 2014, Rodriguez-Silva 2015, Valdesalici 2016, 2019, Valdesalici et al. 2016, Volcan et al. 2018, Berkenkamp 2020, Drawert 2022).

3. Posterior margin of the anal fin in males rounded (vs. pointed in Austrofundulus and Llanolebias , and pointed and frequently with long filaments in Cynolebias ) ( Costa 2001, 2014b, 2017a; Hrbek et al. 2005, Hrbek and Taphorn 2008, Costa et al. 2010).

4. Absence of scales on suborbital region (vs. present in Spectrolebias , Cynolebias and Hypsolebias ) ( Costa 2007a, 2010, Costa et al. 2014b, 2018a, 2018b, Britzke et al. 2016, Costa and Amorim 2018).

Synapomorphies: The genus group Austrolebias was recovered as monophyletic and supported by eight molecular characters and the following 17 morphological characters (see Supporting Information, Appendix S5): dark grey suborbital bar (character:state 25:1); dark grey dashed bars or spots on flank in females (45:2); deep blue iridescent coloration of the opercular region (28:1); absence of filaments projecting distally on dorsal fin of males (48:0); posterodistal edge of anal fin rounded in males (49:1); absence of scales on the basal portion of the anal fin in males (52:0); 10–13 pectoral fin rays (64:0); anterior nostrils pointing dorsolaterally (72:1); frontal squamation pattern F or other (76:3); absence of scales in suborbital region (77:0); close proximity of the urogenital papillae to the anal fin in males (82:1); bone support of contact organs in the pectoral fins of males absent (89:0); extension of the ventral process of the angulo-articular short, retro-articular projecting slightly below the ventral process of the angulo-articular (123:2); dorsal process of angulo-articular medium sized (127:1); cartilage proportion of basihyal 45–70% (133:1); urohyal shape high (135:1); length of extension of broad dorsal portion of cleithrum, relative to vertical distance between dorsal margin of scapula and ventral margin of coracoid, about twice as high (184:2).