Abstract
The species of Hisonotus from the laguna dos Patos system are reviewed. Two species with wide distributions are redescribed: Hisonotus laevior and H. nigricauda. Six new species are described from that system: H. notopagos from the rio Camaquã drainage; H. carreiro and H. prata, endemic from the headwaters of rio Taquari drainage; H. vireo, widely distributed in the rio Jacuí basin; and H. brunneus and H. heterogaster restricted to tributaries of the rio Jacuí drainage. Hisonotus leptochilus is here considered a junior synonym of H. laevior. Hisonotus armatus, H. charrua, H. leucofrenatus, and H. taimensis are also present in the region and in total there are twelve species of Hisonotus in the laguna dos Patos system. Their distributions are discussed, species are illustrated and a taxonomic key is provided.
Highlights
Hisonotus is part of the Hypoptopomatinae, a group of small loricariids including more than 100 species grouped in 19 genera (Schaefer, 2003; Reis & Carvalho, 2007; Carvalho et al, 2008), distributed in the cis-Andean drainages from Venezuela to northern Argentina
Hisonotus was resurrected by Schaefer (1998) and diagnosed by having reduced or absent snout plates anterior to nares, yielding a large paired unplated region in either side of midline from rostrum to nostril, and by having the margins of rostral plates thickened with enlarged odontodes
Britski & Garavello (2007) stated that some species of the genus do not present the diagnostic characters proposed by Schaefer (1998), including Hisonotus notatus its type species
Summary
Hisonotus is part of the Hypoptopomatinae, a group of small loricariids including more than 100 species grouped in 19 genera (Schaefer, 2003; Reis & Carvalho, 2007; Carvalho et al, 2008), distributed in the cis-Andean drainages from Venezuela to northern Argentina. Regan (1904) conducted the first revision of loricariids, and placed Hisonotus, Parotocinclus Eigenmann & Eigenmann, 1889 and Microlepidogaster Eigenmann & Eigenmann, 1889 under the synonymy of Otocinclus Cope, 1871. Hisonotus was resurrected by Schaefer (1998), being diagnosed by reduced or absent snout plates anterior to the nostril, rostrum with enlarged odontodes, and plates forming the lateral rostral margin thickened (Schaefer, 1998: 387). Those diagnostic features were discussed by Britski & Garavello (2007: 6), being considered variable among species of Hisonotus
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