Stethaprioninae Eigenmann, 1907

Melo, Bruno F, Ota, Rafaela P, Benine, Ricardo C, Carvalho, Fernando R, Lima, Flavio C T, Mattox, George M T, Souza, Camila S, Faria, Tiago C, Reia, Lais, Roxo, Fabio F, Valdez-Moreno, Martha, Near, Thomas J & Oliveira, Claudio, 2024, Phylogenomics of Characidae, a hyper-diverse Neotropical freshwater fish lineage, with a phylogenetic classification including four families (Teleostei: Characiformes), Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 202 (1), pp. 1-37 : 22-23

Stethaprioninae Eigenmann, 1907 , new usage

Type genus: Stethaprion Cope, 1870 .

Included genera: Brachychalcinus Boulenger, 1892 , Ectrepopterus Fowler, 1943 , Moenkhausia (in part), Orthospinus Reis, 1989 , Poptella Eigenmann, 1908 , and Stethaprion .

Definition: The least inclusive crown clade that contains Stethaprion erythrops and Moenkhausia dasalmas Bertaco et al., 2011 . This is a minimum-crown-clade definition. See Figure 6 for a reference phylogeny of Stethaprioninae .

Etymology: From the ancient Greek στῆθος (stˈiːθo͡ʊz) meaning breast and πΡίων (pɹˈa͡ɪən) meaning a saw.

Remarks: When first described, the subfamily Stethaprioninae included Stethaprion , Fowlerina Eigenmann, 1907 (= Poptella ), and Brachychalcinus (Eigenmann, 1907) . A taxonomic revision of Stethaprioninae added Orthospinus þanciscensis (Eigenmann, 1914)to the subfamily and identified the presence of a bony spine

directed anteriorly, preceding the first dorsal-fin ray as a synapomorphy for the group ( Reis 1989). Within Acestrorhamphidae , a predorsal spine is unique to Stethaprioninae ; however, the trait is present in other lineages of Characiformes (as expanded pterygiophore or lepidotrichia e.g. Curimatidae , Prochilodontidae , and Serrasalmidae ) ( Reis 1989, Vari 1992, Castro and Vari 2004, Mirande 2010).

In the UCE phylogeny, Moenkhausia dasalmas is resolved as the sister-species of all other lineages of Stethaprioninae ( Fig. 6). Moenkhausia dasalmas was described based on the presence of three unbranched and nine branched dorsal-fin rays (Bertaco et al. 2011). A more detailed study of the tiny first unbranched ray under the skin of M. dasalmas may be useful to establish its relationship with the anteriormost spine in the dorsal fin of the remaining Stethaprioninae . Moenkhausia does not resolve as a monophyletic group in the UCE phylogeny, indicating that M. dasalmas is probably a new and unnamed genus ( Fig. 6).

Previous phylogenies inferred from multilocus DNA sequence and combined molecular and morphological datasets resolved Stethaprioninae as paraphyletic because Gymnocorymbus Eigenmann, 1908 (Pristellinae) was placed as the sister-lineage of a clade of Stethaprioninae containing Brachychalcinus , Orthospinus , Poptella , and Stethaprion ( Oliveira et al. 2011, Benine et al. 2015, Mirande 2019). The UCE inferred phylogeny differs from previous phylogenetic analyses and taxonomic delimitations of Stethaprioninae in resolving both Moenkhausia dasalmas and Ectrepopterus uruguayensis (Fowler, 1943) as closely related to a clade containing Stethaprion , Poptella , Brachychalcinus , and Orthospinus ( Fig. 6; Reis 1989, Oliveira et al. 2011, Benine et al. 2015).

Ectrepopterus was revalidated as distinct from Hyphessobrycon (sensu Eigenmann, 1918) due to the presence of numerous teeth on maxilla (Malabarba et al. 2012), a trait that is absent in all other species of Stethaprioninae (sensu Reis 1989) but present in several other species of the Acestrorhamphidae . Analysis of combined molecular and morphological datasets resulted in phylogenies grouping E. uruguayensis , Hyphessobrycon moniliger Moreira et al., 2002 , three species of Jupiaba , and other lineages of Stethaprioninae ( Mirande 2019) , suggesting future work may discover additional morphological traits consistent with the monophyly of Stethaprioninae . The phylogeny and geographic distribution of Stethaprioninae indicate that La Plata and the Brazilian Shield had an important role in the diversification of the clade ( Fig. 6).