Oligosarcus robustus Menezes, 1969

Serra, Wilson S., Scarabino, Fabrizio, Furtado, Giovanni, Sanguinetti, Germán & Caligari, Mauricio, 2021, Fighting faunistic chaos: confirmations and new records for Uruguayan Characidae (Ostariophysi: Characiformes)., Ichthyological Contributions of PecesCriollos 77, pp. 1-9 : 3

Oligosarcus robustus Menezes, 1969

fig. 3

Examined material: Uruguay: Cerro Largo: MHNM 4429 , 2 ex., 109.0- 124.5 mm SL, Río Yaguarón , 32°31'01"S 53°27'27"W, col. W.S. Serra, G. Furtado & A. Balao, 30-31/III/2018 ; MHNM 4430 , 1 ex., 91.8 mm SL, Cañada de las Pajas, Paso de las Mercedes, 32°30'34"S 53°31'04"W, col. W.S. Serra, G. Furtado & A. Balao, 1/IV/2018 . Treinta y Tres : MHNM 4427 , 1 ex., 87.2 mm SL, Laguna Arnaud, 33°15'00"S 54°22'55"W .

This species differs from other congeners of the genus by the following combination of characters: 16-18 transverse scale rows above lateral line, 75-85 perforated scales in the lateral series, 28-32 horizontal scale rows around caudal peduncle, maxillary, premaxillary and dentary teeth unicuspidate and tip of pectoral fins surpassing the origin of pelvic fins ( Menezes 1969; Menezes & Ribeiro 2015; Ribeiro & Menezes 2015).

Analyzed specimens present all these characters and come from eastern and northeastern Uruguay, associated to the Merín Lagoon basin ( fig. 7 ). The previously known distribution of O. robustus extended through Patos-Merin Lagoon basin and Tramandaí system in Rio Grande do Sul, Brazil (Ribeiro & Menezes 2015).

The species was first recorded for the country by Menezes (1969), who analyzed three specimens ( MZUSP [ex DZSASP] 4679 to 4681, paratypes) from Salto Chico (Salto Department). Menezes (1987: 29) redetermined these lots as Oligosarcus oligolepis (Steindachner, 1867) , an extremely similar species distributed in La Plata, Uruguay, Paraguay and lower Paraná river basins ( Fricke et al. 2021b). Teixeira de Mello et al. (2005) mentioned O. robustus as a new record for Uruguay in a congress abstract, but they did not provide any information about vouchers or precise localities. Aside from these, Soutullo et al. (2009) mentioned it in a technical report as a conservation priority for the SNAP (Sistema Nacional de Áreas Protegidas), but lacking distributional or voucher data. In later versions of the list ( Loureiro et al. 2013) the species was not included. The specimens here analyzed confirm with vouchers the presence of O. robustus for the Uruguayan territory.

Figures

fig. 7 Distribution map of the recorded species: yellow = Aphyocharax rathbuni; green = Oligosarcus robustus; red = Psalidodon erythropterus; blue = Pseudocorynopoma stanleyi. Triangles = records from Uruguay; circles = records from outside Uruguay based on literature. Py. = Paraguay; Uy. = Uruguay.