Mylossoma Eigenmann & Kennedy, 1903

Mateussi, Nadayca T. B., Oliveira, Claudio & Pavanelli, Carla S., 2018, Taxonomic revision of the Cis-Andean species of Mylossoma Eigenmann & Kennedy, 1903 (Teleostei: Characiformes: Serrasalmidae), Zootaxa 4387 (2), pp. 275-309 : 277-279

Mylossoma Eigenmann & Kennedy, 1903

Mylossoma Eigenmann & Kennedy, 1903: 530 [original description; type-species by monotypy Myletes albiscopus Cope, 1872 ].—Eigenmann, 1903: 148 [short diagnosis, etymology].— Norman, 1929: 812 [revision].— Gosline, 1951: 27 [brief description].— Géry, 1976: 48 [checklist of Serrasalmidae , key to genera].— Géry, 1977: 258 [comments on the genus].— Machado-Allison & Castillo, 1992: 1 –34 [morphological study on species from Venezuela].— Jégu, 2003: 187 [checklist of valid species, synonimical list].

Starksina Fowler, 1907: 476 [original description; type-species by monotypy Myletes herniarius Cope, 1872 ]. Mylosoma (sic). — Eigenmann, 1910: 444 [checklist].— Eigenmann, 1915: 261, 265 [diagnosis in key].

Diagnosis. Mylossoma can be distinguished from the remaining Serrasalmidae genera by a single exclusive character: convex edge of anal fin with median and posterior rays longer than anterior ones ( Fig. 1 ), and by the combination of the following non-exclusive characters: 1) absence of spine preceding the dorsal fin; 2) accessory scales covering intersection of main scales, mainly at the anterior portion of the body; 3) scales covering at least the first third of the anal fin; 4) adipose fin never rayed, entirely covered by scales in adults; 5) perforated lateral line scales with one, two or four perforations per scale; 6) two rows of robust teeth in the premaxilla ( Fig. 2 ); 7) a pair of conical teeth behind the main dentary teeth row ( Fig. 2 ); 8) highly developed spines in the ventral keel.

Remarks. Eigenmann & Kennedy (1903) did not provided a diagnosis for Mylossoma , but rather merely assigned Myletes albiscopus to this genus, indicating it as a new generic name, at a footnote. Shortly after, Eigenmann (1903) presented a brief diagnosis for the genus, comparing it with Colossoma . Eigenmann (1915) and Norman (1929), in their revisions of the Serrasalmidae , described several additional species of Mylossoma but the genus remained without a formal diagnosis until Gosline (1951).

Géry (1976) provided diagnosis and synonymic lists for the genera of Serrasalmidae , commented on the synonym of Starksina with Mylossoma , and in addition followed Norman (1929) in recognizing five valid Mylossoma species. Subsequently, Géry (1977) briefly commented the morphology, allometry, and distribution of the valid Mylossoma species, and provided a brief diagnosis for each of them.

A more detailed analysis of Mylossoma was presented by Machado-Allison & Castillo (1992) on a paper about the species of the genus occurring in Venezuela. These authors analysed allometry, ontogenetical changes in the color pattern, and recognized as valid only M. acanthogaster , M. aureum and M. duriventre . Jégu (2003) followed Machado-Allison & Castillo (1992) in recognizing only three valid species for the genus.

The genus Mylossoma has a broad geographical distribution, including the Lago Maracaibo basin in trans- Andean South America , and at the cis-Andean South America, throughout the Amazon basin, including the Tocantins-Araguaia system, and is also widely distributed in the rio Orinoco and at the La Plata basin, with the exception for the upper rio Paraná and upper rio Uruguai basin ( Fig. 3 ).

Figures

FIGURE 2. Mylossoma albiscopum premaxillary (pmx) and dentary (den), INPA 45467, Careiro da Várzea, lagos do Catalão, Amazonas, Brazil.

FIGURE1. Mylossoma albiscopum, freshly collected,126 mm SL, IgarapéBelmont, right margin of rio Madeira, downstream the CachoeiraSanto Antônio(nowadays UHE SantoAntônio), 08°38'36''S 63°51'05''W, not preserved.Photo by Bruno Barros.

FIGURE3. Geographic distributionof the four Cis-Andean Mylossomaspecies.One dot may represent more than one locality. Red circles: M. albiscopum; yellow triangles: M. aureum; purple squares: M. duriventre; orange diamonds: M. unimaculatum. Mylossoma aureum is also recorded for the Río Orinoco basin (see text).