Trichomycterus alterus (Marini, Nichols & LaMonte 1933)

Material examined. 10 exemplars; 32.5 - 34.6 mm SL. CI FML 7841, 4 ex, 27° 19’ 07.5”S, 65° 41’ 51.2”W Jaya River. CL FML 7843, 3 ex, 27° 19’ 07.5”S, 65° 41’ 51.2”W Jaya River. Cl FML 7942, 2 ex, 27°12’ 36.21”S; 65°37’ 22.80”W Pueblo Viejo River. Cl FML 7943, 1 ex, 27° 17’ 39.8”S, 65° 51’ 02.0” W Jaya River .

Identification. Lack of a thick, rugose layer of fatty tissue on body and head; small or not visible body papillae; approximately triangular head shape in dorsal view; operculum and interoperculum with odontodes directed towards posterior region; without mentonian barbels; without adipose fin; first pectoral-fin ray as a distinct filament; 12 principal caudal-fin rays and distal margin concave; unpigmented region on the body anteroventral region to dorsal-fin origin, white dots at origin and end of dorsal-fin base (Fernández and Vari, 2002; Fernández et al., 2017).