Hisonotus brunneus, Carvalho & Reis, 2011

Carvalho, Tiago Pinto & Reis, Roberto E., 2011, Taxonomic review of Hisonotus Eigenmann & Eigenmann (Siluriformes: Loricariidae: Hypoptopomatinae) from the laguna dos Patos system, southern Brazil, Neotropical Ichthyology 9 (1), pp. 1-48 : 38-40

Hisonotus brunneus , new species

Figs. 4g, 8g, 40, and 41

Hisonotus sp. 3 . -Reis & Carvalho, 2007: 84 [listed].

Holotype. MCP 44516, 41.5 mm SL, female, Brazil, Rio Grande do Sul, Cruz Alta, rio Passo Novo, on road from Cruz Alta to Ibirubá , rio Jacuí drainage, 28º38’43”S 53º33’35”W, 2 Apr 1999, R. E. Reis, E. H. L. Pereira & V. A. Bertaco.

Paratypes. All from Brazil, Rio Grande do Sul, rio Jacuí drainage : MCP 22701, 27 + 3 c&s, 26.3-41.1 mm SL, collected with the holotype . ANSP 188705 , 4 , 34.6 -39.0 mm SL ; MCP 41072, 13 , 29.0-41.0 mm SL ; MZUSP 104947 , 4 , 37.2-40.9 mm SL; collected at the type locality, 13 Dec 2006 , T. P. Carvalho & A . R. Cardoso .

Diagnosis. Hisonotus brunneus differs from its congeners, except from H. aky , H. brunneus , H. carreiro , H. charrua , H. heterogaster , H. laevior , H. megaloplax , H. montanus , H. nigricauda , H. notopagos , H. prata , H. ringueleti , and H. taimensis by having the anterior portion of snout with an odontode-free band ( Fig.41), vs. snout completely covered with odontodes. It differs from those above, except from H. laevior , H. taimensis , H. megaloplax , and H. heterogaster by a darkly pigmented caudal fin, without a hyaline area in the middle portion, vs. caudal fin with hyaline areas in the middle portion. Hisonotus brunneus differs from H. heterogaster , H. laevior , H. megaloplax , and H. taimensis by having the abdominal median plate series large, one or two series of plates regularly arranged between the lateral abdominal series ( Fig. 8g), vs. abdominal median plate series with several small plates irregularly arranged between the lateral abdominal plates in H. laevior and H. taimensis , or abdominal medium series absent, midline portion of the belly naked in H. heterogaster ( Fig. 8h) or covered by the enlarged lateral series in H. megaloplax , respectively.Also, it differs from H. heterogaster , H. laevior , H. megaloplax , and H. taimensis by having median lateral plate series incomplete, truncated ( Fig. 4g), vs. median lateral plate series complete, not truncated.

Description. Morphometrics and meristics in Table 11. Adult size small to median for members of this genus (usually less than 40.0 mm SL). Body relatively stocky, robust, without conspicuous keels. Caudal peduncle round in cross section. Dorsal profile convex from tip of snout to parietosupraoccipital tip, slightly convex from that point to dorsalfin origin. Dorsal-fin base straight and posteroventrally sloped, straight from posterior end of dorsal-fin base to caudal-fin origin. Ventral profile almost straight from snout tip to anal-fin origin, concave from this point to caudal-fin origin. Greatest body depth at dorsal-fin origin. Least body depth at posterior end of caudal peduncle. Posterior profile of caudal fin concave to slightly forked. Head and snout broad, snout rounded to slightly square in dorsal view, body progressively narrowing posterior of pelvic-fin insertion. Snout region anterior of nares concave, interorbital region convex. Upper margin of orbit slightly elevated. Eye dorsolaterally positioned. Iris operculum present.

Pectoral fin I,6. Pectoral-fin posterior margin slightly rounded to straight, when depressed tip extending just anterior to middle of pelvic fin. Posterior margin of pectoral-fin spine smooth in adults, juveniles with feeble serrae along distal third of pectoralfin spine. Pectoral-fin axillary slit present, located below posterior bony margin of cleithral process. Pelvic fin i,5. Tip of depressed fin just reaching anal-fin origin in females, but extending far beyond that point in males. Dorsal-fin II, 7. Dorsalfin origin located slightly posterior to vertical through pelvicfin origin. Dorsal-fin spinelet slight-laterally extended.Anal i,5. First anal-fin pterygiophore exposed anterior to anal fin. Adipose fin absent. Caudal fin i,14,i.

Body almost entirely covered by plates except for region overlying opening of swim bladder capsule, area between pectoral girdle and lower lip, region around anus, and area around base of paired fins. Rostral plate with posterior notch articulation of mesethmoid. Rostral plate thickened, with odontode-free area between dorsad and ventrad series of odontodes ( Fig. 41). Snout plates anterior to nares reduced, small unplated area at lateral portion between rostral plate and nostril. Three rows of predorsal plates. Lateral line incomplete, with gap without pores along middle length of body. Median plate series truncated, not reaching posterior end of caudal peduncle ( Fig. 4g). Abdominal plates arranged in three rows anteriorly and irregularly arranged between pelvic-fin insertions. Lateral abdominal plates slightly larger and forming regular series. Median abdominal series formed by one or two plate series, pre-anal shield region formed by median to large plates ( Fig. 8g). Coracoid and cleithrum exposed and covered by odontodes, except for median region of cleithrum between arrector fossae openings and medial region of coracoids.

Odontodes on parieto-supraoccipital tip slightly larger than those of surrounding areas, most in smaller specimens. Head, fin-spines, and body plates covered with odontodes, larger on anterior surface of all fin spines, and on ventral margin of rostrum slightly enlarged in dorsal margin. Odontodes medially directed on pelvic-fin unbranched ray. Anterior margin of compound pterotic with median-to-large size perforations. Infraorbital canal entering infraorbital series via compound pterotic. Lips roundish and papillose, posterior margin of lower lip fimbriate. Maxillary barbel present.

Premaxillary and dentary teeth slender proximally and flattened distally; bifid, major (medial) cusp large and rounded, minor (lateral) minute pointed. Accessory patch of teeth absent on dentary and premaxilla.

Compound ventral hypural plate (hypurals 1-2) and compound dorsal hypural plate (hypurals 3-5) completely fused to each other, with small median notch on the posterior margin of caudal-fin skeleton. Total vertebrae 27-28 (2 c&s).

Color in alcohol. Ground color of dorsal and lateral surfaces pale to dark brown. Dorsal and lateral body surfaces with rounded gray spots. Dorsal and lateral portions of head darker than body, except for lighter area in ventrolateral region contrasting with dark blotches. Ventral surface of body pale yellow, except for scattered chromatophores. Region anterior to nares lighter than surrounding areas, forming longitudinal light stripe from snout tip to posterior end of parietosupraoccipital. Unbranched rays of fins mostly brown pigmented, sometimes presenting hyaline transverse bands, forming striped pattern. Caudal fin almost completely brown, except for hyaline area on posterior end of upper caudal fin rays. Unbranched rays of caudal fin with alternating transverse light bands and dark areas. General color pattern in life, dark green.

Sexual dimorphism. Urogenital papilla, positioned just behind the anal opening in males. Adult males also possess a developed fleshy flap along the dorsal margin of first thickened pelvic-fin ray, that is absent in females. Flap slightly wider basally and progressively narrowing distally. Presence of a fleshy flap in the medial portion of the first and second branched rays of pelvic fin. In juvenile males, flaps smaller or absent. Males have longer pelvic-fin unbranched ray that extends far beyond anal-fin origin, with pelvic-fin reaching just to anal-fin origin in females.

Distribution and habitat. Hisonotus brunneus is endemic to the upper rio Jacuí basin, in the laguna dos Patos system. The new species is only known from the rio Passo Novo, an affluent of the rio Ingaí, tributary to the upper portion of rio Jacuí basin ( Fig. 32). This species inhabits a median to fast flowing watercourse, with clear to brown waters running over sand or stones. Being found in marginal submersed grasses, H. brunneus is collected in the vegetation together with Eurycheilichthys limulus Reis & Schaefer. The rio Passo Novo at the type locality is a small creek, about 3 m wide and shallow with a maximum depth of 0.5 m, at 400 m above sea level. The stream is somewhat polluted, crossing the urban area of Cruz Alta, and has deforested riparian vegetation and amounts of rubbish along the margins.

Etymology. The specific epithet brunneus , from the Latin, means tawny and refers to overall brownish pigmentation of the species. It is treated as an adjective.