Hisonotus taimensis (Buckup, 1981)

Figs. 6b and 20b

Microlepidogaster taimensis Buckup, 1981: 22 (original description, type locality:novo canal do arroio Taim, Estação Ecológica do Taim, Rio Grande, Rio Grande do Sul, Brasil). - Buckup & Malabarba, 1983 [listed]. - Malabarba, 1989: 150 [listed]. - Grosser et al., 1994 [listed].

Hisonotus taimensis. - Schaefer, 2003: 323 [listed, new combination]. - Bemvenuti & Moresco, 2005: 55 [listed and illustrated]. - Reis & Carvalho, 2007: 84 [listed]. - Ferraris, 2007: 248 [listed].

Diagnosis. Hisonotus taimensis differs from its congeners, except from H. notopagos and H. laevior by the higher number of lateral plates 26-29 (Table 2), vs. 20-25, by the number of predorsal plates 3-4 (usually 4), vs. 2-3, and by vertebral count 31-32, vs. 25-29 vertebrae. Hisonotus taimensis differs from H. notopagos by the presence of a posterior notch articulation in the rostral plate, vs. absence of a notch articulation in the rostral plate, by having a round caudal peduncle in cross section, vs. a slightly square caudal peduncle in cross section, and by having the area anterior to nares unplated, vs. area anterior to nares covered by dermal plates. Hisonotus taimensis can be distinguished from H. laevior by the narrow cleithral width 18.5-21.3% SL, mean 20.0%, vs. 20.6-24.6% SL, mean 22.9% (Fig. 15), and by the lower body depth at dorsalfin origin 13.3-16.3% SL, mean 15.1%, vs. 16.2-20.8% SL, mean 18.1% (Fig. 16).

Description. Morphometrics and meristics in Table 4. This species was described by Buckup (1981) and will not be redescribed here.

Distribution and habitat. Hisonotus taimensis is known from localities nearby the laguna Mirim (Fig. 22). This species inhabits, at type locality, slow flowing watercourses with brown waters of muddy and sandy bottom. The individuals are found in between aquatic vegetation of the genus Eichhornia, in grasses or similar kind of submersed vegetation. According to Buckup (1981) the enlarged rostral and pelvic-fin odontodes contribute to them cling the stems and roots of Eichhornia. See Grosser et al. (1994) for detailed description of the species habitat and distribution in the Taim region.

Material examined. All from laguna dos Patos system, Rio Grande do Sul, Brazil. Paratypes of M. taimensis: MAPA 1054, 1, 36.3 mm SL, Santa Vitória do Palmar, channel at km 114 on highway BR-471, Estação Ecológica do Taim. MAPA 1055, 1059- 1061, 4, 37.5-51.1 mm SL, Rio Grande, channel at east of lagoa do Jacaré, Estação Ecológica do Taim. MAPA 1070, 1, 26.1 mm SL, Santa Vitória do Palmar, old course of arroio Taim, Estação Ecológica do Taim. MAPA 1013, 1014, 1016, 1018, 1019, 1024, 1026-1028, 1063-1065, 1067-1069, 15, 30.1-47.4 mm SL, Rio Grande, new channel of arroio Taim, Estação Ecológica do Taim. MCN 4835-4844, 10, 34.7-45.9 mm SL, Rio Grande, new channel of arroio Taim, Estação Ecológica do Taim. MCN 7660, 2, 23.9- 50.0 mm SL, Rio Grande, north channel of lagoa do Jacaré, Estação Ecológica do Taim. UFRGS 352-353, 2, 40.4-43.5 mm SL, Rio Grande, new channel of arroio Taim, Estação Ecológica do Taim. UFRGS 396, 1, 37.3 mm SL. Rio Grande, new channel of arroio Taim near the highway BR-471. Non-types: MCP 14467, 2 + 3 c&s, 21.8-42.5 mm SL, Rio Grande, new channel of arroio Taim, Estação Ecológica do Taim. MCP 17417, 27 + 3 c&s, 24.6-41.8 mm SL, Rio Grande, new channel of arroio Taim. UFRGS 697, 2, 32.8-37.4 mm SL, Rio Grande, Estação Ecológica do Taim. UFRGS 2462, 5, 21.1-42.3 mm SL, Rio Grande, Estação Ecológica do Taim, curve in the new channel of arroio Taim on highway BR-471. UFRGS 2583, 1, 36.2 mm SL, Rio Grande, Estação Ecológica do Taim, southeast margin of lagoa das Flores. MCN 6474, 1, 46.2 mm SL, Chuí, Barra do Chuí, 33º44’S 53º22’W. CIMC 2341, 2, 28.0- 30.7 mm SL, Rio Grande, canal near Estação Ecológica do Taim. CIMC 2405, 67, 20.6-37.3 mm SL, Capão do Leão, canal São Gonçalo near sanga das Traíras. INPA 791, 1, 47.5 mm SL, Rio Grande, arroio Bolacha. INPA 790, 2, 25.1-44.1 mm SL, Rio Grande, arroio Senandes.