Description of a new catfish genus (Siluriformes, Loricariidae) from the Tocantins River basin in central Brazil, with comments on the historical zoogeography of the new taxon Author Silva, Gabriel S. C. Author Roxo, Fabio F. Author Ochoa, Luz E. Author Oliveira, Claudio text ZooKeys 2016 598 129 157 http://dx.doi.org/10.3897/zookeys.598.7400 journal article http://dx.doi.org/10.3897/zookeys.598.7400 1313-2970-598-129 5331A38A1FE8460CB4C249E9D7ECC3FA 5331A38A1FE8460CB4C249E9D7ECC3FA Taxon classification Animalia Siluriformes Loricariidae Microplecostomus gen. n. Figs 1, 6 Type species. Microplecostomus forestii sp. n. Diagnosis. The new genus and species differs from all members of the Loricariidae by having (1) three hypertrophied bicuspid odontodes on the lateral portion of the body (character apparently present only in mature males - observed in the holotype , but not present in the paratypes ) (Fig. 2a, b); and differs from all members of the Neoplecostominae by having (2) a large area without odontodes around the snout, observed in all specimens, Fig. 3 (vs. margin of snout bearing odontodes); and from all members of the Neoplecostominae , except Hirtella carinata Pereira, Zanata, Cetra & Reis, 2014, Pareiorhina carrancas Bockmann & Ribeiro, 2003 and Pareiorhina hyptiorhachis Silva, Roxo & Oliveira, 2013 by (3) the presence of a post-dorsal ridge on the caudal peduncle, see dorsal view of holotype in Figs 1, 4 (vs. the absence of a post-dorsal ridge). Microplecostomus forestii sp. n. differs from species of the genera Isbrueckerichthys , Neoplecostomus and Pseudotocinclus by (4) the absence of abdominal plates, Fig. 1 (vs. abdomen covered by pentagonal or hexagonal platelets); from Kronichthys by having (5) the tooth series in dentary and premaxillary rows straight (vs. tooth series strongly curved medially); from Neoplecostomus by (6) the absence of a conspicuous series of enlarged papillae just posterior to the dentary teeth (vs. presence of enlarged papillae); and from Pseudotocinclus by having (7) the caudal peduncle ellipsoid in cross section (vs. caudal peduncle square in cross-section). Figure 1. Microplecostomus forestii sp. n., MZUSP 118673, holotype , male, 38.3 mm SL, Goias state, Brazil, Tocantins River basin. Figure 2. Photographs showing a the three hypertrophied bicuspid odontodes on the lateral portion of the body of the holotype of Microplecostomus forestii sp. n., MZUSP 118673; b Detail of the hypertrophied bicuspid odontodes. Figure 3. Microplecostomus forestii sp. n. showing a large area without odontodes around the snout, LBP 19017, 29.0 mm SL. Figure 4. Dorsal view of the caudal peduncle in Microplecostomus forestii sp. n., LBP 19017, 29.0 mm SL, showing the presence of a series of unpaired median plates that form a post-dorsal ridge. Etymology. The generic name is a combination of Greek, micro ( mikros ) = small, related to the small size of the adult type-specimen, and plecostomus = a former generic name of species currently included in Loricariidae , also in reference to the small adult size of the type-species. A masculine name.