Rhinolekos, a new genus with three new species of Hypoptopomatinae (Siluriformes: Loricariidae) from upper rio Paraná

65 Neotropical Ichthyology, 9(1):65-78, 2011 Copyright © 2011 Sociedade Brasileira de Ictiologia Rhinolekos, a new genus with three new species of Hypoptopomatinae (Siluriformes: Loricariidae) from upper rio Paraná Fernanda de Oliveira Martins and Francisco Langeani Rhinolekos, new genus, and three new species, R. britskii, R. garavelloi, and R. schaeferi, are described from rio Paranaíba, upper rio Paraná drainage, central Brazil. Rhinolekos can be diagnosed by the following combination of characters: anterior portion of the compound supraneural-first dorsal-fin proximal radial contacting the neural spine of the 9th or 10th vertebrae; presence of the lateronasal plate; absence of the median rostral plate; presence of the pectoral-fin axillary slit just in juvenile specimens; ventral surface of pectoral girdle exposed only laterally; arrector fossae partially enclosed, with opening relatively large, extending laterally halfway towards pectoral-fin base; paired anterior process of the compound supraneural-first dorsalfin proximal radial bone absent; median plate series continuous to the caudal-fin origin; iris operculum present; pteroticsupracleithrum quadrangular in shape and not extending posteriorly; supraoccipital not contributing to the dorsal portion of the swimbladder capsule; subopercular plate present; dorsal and ventral margins of snout bearing odontodes roughly equivalent in size and shape to those on remainder of the head; caudal peduncle roughly rounded in cross section; longitudinal crests in supraoccipital absent; fourth infraorbital expanded ventrally. Rhinolekos, gênero novo, e três espécies novas, R. britskii, R. garavelloi e R. schaeferi, são descritas do rio Paranaíba, drenagem do alto rio Paraná, região central do Brasil. Rhinolekos pode ser diagnosticado pela seguinte combinação de caracteres: porção anterior do composto supraneural-primeiro proximal radial da nadadeira dorsal contatando o espinho neural da nona ou décima vértebra; presença da placa látero-nasal; ausência da placa rostral mediana; presença da fenda peitoral axilar apenas nos juvenis; superfície ventral da cintura peitoral exposta apenas lateralmente; arrector fossae parcialmente fechado, abertura relativamente grande, estendendo-se em direção à base da nadadeira peitoral; processo anterior pareado do composto supraneural-primeiro proximal radial da nadadeira dorsal ausente; série mediana de placas contínua até a origem da nadadeira caudal; opérculo da íris presente; pterótico-supracleitro quadrangular, não se estendendo posteriormente; ausência de cristas no supraoccipital, este não contribuindo com a formação da porção dorsal da cápsula da bexiga natatória; placa subopercular presente; margens dorsal e ventral do focinho portando odontódes de tamanho e forma equivalentes aos demais da cabeça; pedúnculo caudal aproximadamente circular em corte transversal; quarto infraorbital expandido ventralmente. Key words: Cascudinhos, Neotropical region, rio Paranaíba, Systematics, Taxonomy. UNESP - Universidade Estadual Paulista, Instituto de Biociências, Letras e Ciência Exatas, Departamento de Zoologia e Botânica, Laboratório de Ictiologia. Rua Cristóvão Colombo, 2265, 15054-000 São José do Rio Preto, SP, Brazil. [email protected] Introduction The Hypoptopomatinae is considered a monophyletic group of the Loricariidae, including more than 80 species arranged in 19 genera (Reis & Carvalho, 2007; Carvalho et al., 2008). Most hypoptopomatines are small-sized fishes, ranging from 20 to 35 mm in standard length, and are usually found in close association with marginal vegetation (Schaefer, 2003). In the last fifteen years, seven new genera and many new species were described for this subfamily, indicating the great diversity of this group that still remains fairly known. During samplings in headwater streams of the rio Paranaíba, upper rio Paraná drainage, specimens of two new species of hypoptopomatines were captured. Additionally, examination of material from rio Paranaíba deposited in the fish collection of Museu de Ciências e Tecnologia da Pontifícia Universidade Católica do Rio Grande do Sul (MCP) prompted the discovery of another related new species. After comparisons, these species were not diagnosable within any previously described Hypoptopomatinae genus or species, therefore a new genus is proposed and three new species are described. A new genus and three new species of Hypoptopomatinae 66 Material and Methods Measurements were made with digital calipers, point-topoint on the left side of the specimens, to the nearest 0.1 mm, following Boeseman (1968) with modifications of Armbruster & Page (1996), Schaefer & Provenzano (1993), and Ribeiro et al. (2005). Head length was measured from the tip of the snout to the posterior tip of the supraoccipital. Plate counts followed Schaefer (1997) and nomenclature followed Bailey & Baskin (1976) and Schaefer (1997). Plates and teeth were counted from both sides in cleared and stained (c&s) specimens, prepared according to Taylor & van Dyke (1985). Vertebrae counts included five from Weberian apparatus, and the compound caudal centrum was counted as a single element. Dorsal-fin rays counts include spinelet as the first unbranched ray. Museum abbreviations for specimens examined are listed in Fricke & Eschmeyer (2010) with the addition of LBP (Laboratório de Biologia de Peixes, UNESP, Botucatu, Brazil), cited therein erroneously as LPB. Results Rhinolekos, new genus Type species. Rhinolekos britskii, new species. Diagnosis. Rhinolekos differs from all other Hypoptopomatinae (sensu Schaefer, 1998) (except Microlepidogaster Eigenmann & Eigenmann) by having the anterior portion of the compound supraneural-first dorsalfin proximal radial contacting the neural spine of the 9th or 10th vertebrae (Fig. 1) (vs. 8th in Epactionotus Reis & Schaefer and 7th in all other hypoptopomatines). Also, Rhinolekos can be readily distinguished from the remaining Hypoptopomatinae (except Gymnotocinclus anosteos Carvalho, Lehmann & Reis and Acestridium Haseman) by the presence of the lateronasal plate, a large plate between the second infraorbital plate and the nasal opening, anteriorly projected, surrounding the nostril (Fig. 2). Rhinolekos differs from Gymnotocinclus anosteos by having: dermal plates covering most of the body (vs. extreme reduction of body dermal plates); lateral connecting bone fused to the lateral body plates (vs. absence of lateral connecting bone); bifid hemal spines on caudal vertebrae posterior to first anal-fin proximal radial present (vs. bifid hemal spines absent); all lateral body dermal plates with odontodes posteriorly curved, including the last ones on the caudal peduncle (vs. odontodes on last dermal plates dorsally or anteriorly curved); maxillary barbel reduced, free from lower lip (vs. adnate to lower lip). Furthermore, Rhinolekos differs from Acestridium by having: preopercle emergent to skin surface and visible externally (vs. preopercle not emergent and not visible externally in all Hypoptopomatini taxa, including Acestridium); head and body relatively wide, not depressed (vs. head and body very slender, depressed); anterior margin of snout markedly rounded, without projection (vs. snout with a conspicuous spatulate projection); dorsal-fin insertion slightly posterior to pelvic-fin base (vs. dorsal fin placed well posterior to pelvic fin and just anterior to anal-fin origin). Rhinolekos is similar to Microlepidogaster and Pseudotocinclus Nichols, concerning general body shape and may be phylogenetically related with these genera. However, Rhinolekos differs from Microlepidogaster by having ventral surface of pectoral girdle exposed only laterally (vs. totally exposed); arrector fossae partially enclosed, with opening relatively large, extending laterally halfway towards pectoral-fin base (vs. opening reduced). Additionally, Rhinolekos differs from M. perforatus by the absence of the median rostral plate (vs. presence); by presenting the pectoral-fin axillary slit only in juvenile specimens (vs. pectoral-fin axillary slit present, even in adult specimens); paired anterior process of the compound supraneural-first dorsal-fin proximal radial bone absent (vs. present, linking the supraneural with the supraoccipital via ligament); median plate series continuous to the caudal-fin origin (vs. median plate series truncated, ending before the caudal-fin base), and iris operculum present (vs. absent). Finally, Rhinolekos differs from Pseudotocinclus by having the caudal peduncle roughly rounded in cross section (vs. caudal peduncle distinctly square in cross section); longitudinal crests in supraoccipital absent (vs. present); fourth infraorbital expanded ventrally (vs. not expanded). Distribution. Rhinolekos is restricted to streams of the rio Paranaíba drainage, Goiás State, central Brazil (Fig. 3). Etymology. The generic name is a combination of the greek, rhinos = nose, nostril and lekos = plate, in reference to presence of the lateronasal plate. Gender masculine. Key to species of Rhinolekos 1. Premaxillary and dentary accessory teeth present; caudal peduncle shallow (7.7-8.7% of SL); 18-20 (mode 19) middorsal plates........................................Rhinolekos schaeferi 1’. Premaxillary and dentary accessory teeth absent; caudalpeduncle deep (greater than 9.0% of SL); 21-27 (mode 22 in R. britskii and 24 or 25 in R. garavelloi) mid-dorsal plates........................................................................................2 2. Transverse dark band in pectoral, pelvic and anal-fin rays present; thoracic length 14.7-18.0% SL; 24-28 dorsal plates.......................................................Rhinolekos britskii 2’. Transverse dark band in pectoral, pelvic and anal-fin rays absent; thoracic length 18.1-20.8% SL; 30-35 dorsal plates................................................Rhinolekos garavelloi F. O. Martins & F. Langeani 67 Fig. 1. Anterior portion of axial skeleton and dorsal-fin supports (left side, lateral view). a) Rhinolekos britskii, DZSJRP 6489, 28.0 mm SL. b) Rhinolekos garavelloi, DZSJRP 10477, 30.4 mm SL. c) Rhinolekos schaeferi, DZSJRP 12192, 36.5 mm SL. Scale bar = 1 mm. Vertebrae counts included five from the Weberian apparatus. RV6 = rib of sixth vertebra; PX2-3 = compound proximal and medial radial 2-3; SN+PX1 = compound supraneural first dorsal-fin proximal radial; SP1 = first dorsal-fin spinelet; SP2 = second dorsal-fin spine; V6-12 = vertebrae 6-12. A new genus and three new species of Hypoptopomatinae 68 Rhinolekos britskii Martins, Langeani & Costa, new species Fig. 4 Holotype. DZSJRP 6489, 32.2 mm SL, female, Brazil, Goiás State, Bela Vista de Goiás, tributary of the córrego Arapuca, Fazenda Arapuca, rio Paranaíba drainage, 17º04’06”S 48º43’59”W, 29 Apr 2004, F. Langeani & D. O. Tavares. Paratypes. All from Brazil, Goiás State, rio Paranaíba drainage. DZSJRP 12190, 17, 1 c&s, 21.8-35.5 mm SL (7, 31.9-35.5 mm SL), collected with holotype; DZSJRP 5567, 1, 19.7 mm SL, Bela Vista de Goiás, córrego Arapuca, dirt road of GO-020 (BR-352), 17º06’16”S 48º43’08”W, 22 May 2003, F. Langeani, J. P. Serra, F. R. Carvalho & D. O. Tavares; DZSJRP 5604, 1, 18.4 mm SL, DZSJRP 5608, 1, 36.5 mm SL, Cristianópolis, córrego Gameleira, GO-020 (BR-352) 17º10’19”S 48º43’36”W, 22 May 2003, F. Langeani, J. P. Serra, F. R. Carvalho & D. O. Tavares; DZSJRP 5614, 6, 14.3-34.4 mm SL (2, 33.6-34.4 mm SL), Bela Vista de Goiás, córrego Campo Alegre, 17º09’09”S 48º44’00”W, 22 May 2003, J. P. Serra, F. Langeani, F. R. Carvalho & D. O. Tavares; DZSJRP 6514, 2, 23.7-35.6 mm SL (1, 35.6 mm SL), Bela Vista de Goiás, córrego dos Macacos, Fazenda Arapuca Velha, 17º05’26”S 48º44’04”W, 29 Apr 2004, F. Langeani & D. O. Tavares; DZSJRP 6884, 7, 2 c&s, 22.2-38.2 mm SL (6, 30.7-38.2 mm SL). MZUSP 103698, 6, 26.7-36.3 mm SL (3, 30.7-36.3 mm SL), Bela Vista de Goiás, Corumbá tributary, Fazenda Arapuca, far away 25 km from GO-020, 17º04’08”S, 48º43’59”W, 25 Jul 2004, D. O. Tavares, G. A. Tavares & D. J. Correa Jr.; DZSJRP 6983, 7, 1 c&s, 16.8-40.0 mm SL, Bela Vista de Goiás, córrego dos Macacos, rio Corumbá, GO-020, Km 78, 17º04’39”S 48º43’20”W, 1 Nov 2004, D. O. Tavares, G. A. Tavares & D. J. Correa Jr.; DZSJRP 7018, 12, 1 c&s, 15.0-33.5 mm SL, (1, 33.5 mm SL), DZSJRP 7022, 1 c&s, 31.2 mm SL, MCP 44058, 5, 22.2-36.0 mm SL (2, 32.4-36.0 mm SL), MNRJ 34128, 5, 26.1-35.5 mm SL (3, 31.1-35.5 mm SL), Bela Vista de Goiás, rio Corumbá tributary, GO-020, Km 78, 17º04’08”S 48º44’01”W, 1 Nov 2004, D. O. Tavares, G. A. Tavares & D. J. Correa Jr.; DZSJRP 7036, 2, 37.3-38.0 mm SL (1, 38.0 mm SL), Bela Vista de Goiás, córrego dos Macacos, rio Corumbá, GO-020, Km 78, 17º04’38”S 48º43’18”W, 6 Feb 2005, G. A Tavares, D. J. Correa Jr. & W. C. Carmo; DZSJRP 7042, 6, 19.3-35.3 mm SL (1, 35.3 mm SL), Bela Vista de Goiás, rio Corumbá tributary, GO-020, Km 78, 17º04’07”S 48º43’59”W, 6 Feb 2005, G. A Tavares, D. J. Correa Jr. & W. C. Carmo; DZSJRP 7045, 3, 34.6-37.5 mm SL, Bela Vista de Goiás, rio Corumbá tributary, GO-020, Km 78, 17º05’27”S 48º44’40”W, 6 Feb 2005, G. A. Tavares, D. J. Correa Jr. & W. C. Carmo. Diagnosis. Rhinolekos britskii differs from its congeners by the following characters: transverse dark bands in pectoral-, pelvicand anal-fin rays present (vs. absent); 31 vertebrae (vs. 32), and by anterior portion of the compound supraneuralFig. 3. Southeastern Brazil showing type locality of the Rhinolekos species (1 - rio Corumbá; 2 - rio Paranaíba; 3 - rio Grande; 4 - rio Paraná). Circle - R. britskii; Square - R. garavelloi; Star - R. schaeferi. Fig. 2. Skull of Rhinolekos schaeferi (left side, dorsal view), paratype, DZSJRP 12192, 36.5 mm SL. Scale bar = 1 mm. CP12 = cheek plates; F = frontal; IO1-5 = infraorbitals 1-5; LE = lateral ethmoid; LNP = lateronasal plate; N = nasal; NP = nuchal plate; OP = opercle; PF = prefontral plate; POP = preopercle; PR1-3 = postrostrals plates 1-3; PT-SC = compound pterotic; SOC = supraoccipital; SPH = sphenotic. F. O. Martins & F. Langeani 69 first dorsal-fin proximal radial contacting the neural spine of the 9th vertebra (vs. 10th). Furthermore, R. britskii could be distinguished from R. garavelloi by the larger postanal length (34.7-37.7% in SL vs. 29.0-34.6%); smaller thoracic length (14.718.0% in SL vs. 18.1-20.8%); and fewer plates in the dorsal series (24-28 vs. 30-35). It differs from R. schaeferi by the absence of premaxillary and dentary accessory teeth (vs. presence); and 21-24 mid-dorsal plates (vs. 18-20). Description. Morphometric and meristic data are given in Tables 1 and 2. Dorsal body profile convex from tip of snout to dorsal-fin origin; concave at dorsal-fin base; almost straight to caudal-fin origin. Small elevation at supraoccipital immediately posterior to eyes. Ventral head profile slightly concave. Ventral body profile almost straight from pectoralfin origin to anal-fin origin, ascending at anal-fin base. Greatest body depth at dorsal-fin origin. Greatest body width at opercular region, gradually tapering towards snout and caudal fin. Head without longitudinal crests, anterior margin rounded in dorsal view. Snout without rostral plate, bearing numerous small plates with thin odontodes; most anterior portion of head naked. Odontodes equal in size and uniformly Fig. 4. Rhinolekos britskii, holotype, DZSJRP 6489, 32.2 mm SL, female, tributary of the córrego Arapuca, rio Paranaíba drainage, Bela Vista de Goiás, Goiás State, Brazil. A new genus and three new species of Hypoptopomatinae 70 distributed, not forming rows, on head and body. Eye small, dorsolaterally placed, not visible from ventral view. Iris operculum present, very reduced in some specimens. Infraorbital canal entering infraorbital series via compound pterotic. Compound pterotic roughly quadrangular in shape, without elongate posterior extension, its posteroventral margin with irregular and median to large perforations. Supraoccipital not contributing to the dorsal portion of the swimbladder capsule. Body entirely covered with bony plates, except on ventral part of head, region overlying opening of swim bladder capsule, and around anus and pelvic-fin origin. Abdomen covered with small plates irregularly arranged. Lips roundish, papillose; lower lip larger than upper lip, with papillae gradually smaller towards edges. Maxillary barbel free from lower lip and reduced. Teeth slender, bifid; median cusp larger and rounded, lateral cusp smaller and pointed. Premaxillary teeth 19-28. Dentary teeth 18-25. Number of teeth increasing with size. Premaxillary and dentary accessory teeth absent. Dorsal-fin rays ii,6-7, originating approximately at vertical through middle of pelvic fin; its length surpassing anal-fin origin; spinelet small, approximately rectangular, posterior margin slightly convex; locking mechanism non-functional. Anterior portion of compound supraneural-first dorsal-fin proximal radial contacting neural spine of 9th vertebra (Fig. 1a). Pectoral-fin rays i,6, originating immediately posterior to opercular opening and surpassing pelvic-fin origin. Cleithrum and coracoid exposed and supporting odontodes only laterally, near pectoral-fin insertion. Arrector fossae partially enclosed by ventral lamina of coracoid; opening relatively large, extending laterally halfway towards pectoralfin base. Pectoral-fin axillary slit present only in juvenile specimens. Pelvic-fin rays i,5, reaching anal-fin origin when depressed. Pectoraland pelvic-fin unbranched ray shorter than branched rays; enlarged odontodes at tip of pectoralfin unbranched ray and at mesial margin of pelvic-fin unbranched ray. Anal-fin rays i,5. Caudal-fin rays i,14,i, lower lobe slightly longer than upper lobe; four or five dorsal and four ventral procurrent rays. Adipose fin absent; replaced by single azygous plate in some specimens. Median lateral plates 26-30. Median-plate series complete, from compound pterotic to caudal-fin base, absence of canal in one plate near region of tenth median plate in some specimens. Vertebrae 31. Color in alcohol. Ground color of dorsal surface brown. Trunk with four transverse dark bars: first at dorsal-fin origin, triangular in some specimens; second, ventral to dorsal-fin rays; third at vertical through middle of anal fin; last near caudal-fin insertion. Light brown area between tip of snout and nares. Opercle region unpigmented. Lateral portion of body brown, with dark longitudinal stripe, from compound pterotic to caudal-fin origin. Ventral surface of body mostly unpigmented. Dorsal-, anal-, pectoral-, and pelvic-fins membranes hyaline, with transverse dark bands along rays. Caudal fin densely pigmented, tip of lobes hyaline; some specimens, mainly juveniles, with a circular unpigmented area on each lobe. Procurrent rays sometimes with yellowish white coloration, extending laterally to caudal peduncle. Sexual dimorphism. Males with conspicuous urogenital papillae immediately posterior to anus, and with a dorsal expanded flap of skin in all pelvic-fin rays. Distribution. Streams from rio Paranaíba drainage, upper rio Paraná system, Goiás State, Brazil (Fig. 3). Etymology. Named after Heraldo A. Britski, Museu de Zoologia da Universidade de São Paulo, in recognition of his dedication and remarkable contributions to the studies in Hypoptopomatinae and to Neotropical Ichthyology, in general. Remarks. Filipi Cezaro Costa contributed to the description of Rhinolekos britskii and is therefore included as one of the authors of this species. H Minimum Maximum Mean SD Standard length (mm) 32.2 30.7 38.3 - - Percents of Standard length Predorsal length 46.8 44.1 48.9 46.7 1.3 Preanal length 58.8 55.3 60.0 57.9 1.4 Prepectoral length 25.4 22.4 26.4 25.1 0.9 Prepelvic length 36.1 34.8 39.7 36.7 1.1 Postanal length 35.2 34.7 37.7 36.0 1.0 Thoracic length 17.1 14.7 18.0 16.9 1.0 Abdominal length 21.6 19.5 23.9 21.3 1.0 Caudal-peduncle depth 9.7 9.0 10.8 9.8 0.5 Head length 29.2 27.6 32.3 30.2 1.0 Head width 23.6 22.4 25.3 23.8 0.6 Head depth 13.7 13.1 14.8 14.0 0.5 Base of dorsal-fin length 11.4 9.8 13.3 11.9 0.9 Folded dorsal-fin length 21.7 19.7 24.8 22.3 1.1 Pectoral-fin unbranched ray length 21.7 16.2 23.2 20.8 1.4 Pelvic-fin unbranched ray length 17.0 15.5 20.9 17.5 1.4 Snout-opercle length 24.5 23.2 26.4 25.0 0.8 Percents of Head length Head width 78.8 73.1 82.4 78.7 2.5 Head depth 45.9 42.8 49.3 46.5 1.8 Snout length 54.6 51.6 57.3 54.4 1.4 Orbital diameter 16.9 13.8 18.0 16.2 1.2 Interorbital length 39.7 36.4 41.1 38.8 1.2 Barbel length 6.2 3.5 9.2 6.1 1.1 Prenasal length 37.3 32.3 39.8 36.9 1.8 Internasal length 13.0 10.5 14.2 12.4 1.0 Suborbital depth 24.2 21.9 29.3 25.0 1.6 Table 1. Descriptive morphometrics of Rhinolekos britskii. Values given for holotype (H; DZSJRP 6489) and ranges of 30 specimens (DZSJRP 5614, 6514, 6884, 7018, 7036, 7042, 12190; MCP 44058; MNRJ 34128; MZUSP 103698); range includes holotype. SD = Standard deviation. F. O. Martins & F. Langeani 71 Rhinolekos garavelloi Martins & Langeani, new species Fig. 5 Holotype. DZSJRP 10479, 31.4 mm SL, male, Brazil, Goiás State, Caldas Novas, rio Paranaíba drainage, stream at Fazenda Lageado, near GO-213 road, after rio Corumbá bridge, 17º44’20”S 48º28’27”W, 8 Jun 2007, F. Langeani, L. G. G. Silveira, D. Simiele, M. M. F. Marinho & J. P. Serra. Paratypes. All from same locality of holotype. DZSJRP 10477, 22, 3 c&s, 15.2-36.2 mm SL (11, 31.2-36.2 mm SL), MCP 44057, 6, 24.8-32.2 mm SL (3, 30.6-32.2 mm SL), 11 May 2007, L. G. G. Silveira & F. Langeani. DZSJRP 12191, 37, 4 c&s, 10.7-32.8 mm SL (11, 29.8-32.8 mm SL), MNRJ 34127, 5, 21.4-32.5 mm SL (2, 29.0-32.5 mm SL), MZUSP 103697, 5, 20.0-31.3 mm SL (2, 31.231.3 mm SL), collected with the holotype. Diagnosis. Rhinolekos garavelloi differs from its congeners by the following characters: shorter postanal length (29.034.6% in SL vs. 34.7-37.7% in R. britskii and 35.7-41.3% in R. schaeferi); longer thoracic length (18.1-20.8% in SL vs. 14.718.0% in R. britskii and 13.7-17.6% in R. schaeferi); 30-35 dorsal plates (vs. 24-28 in R. britskii and 26-28 in R. schaeferi). Furthermore, it could be distinguished from R. britskii by the absence of transverse dark bands in pectoral-, pelvicand anal-fin rays (vs. presence); by having 32 vertebrae (vs. 31), and anterior portion of the compound supraneural-first dorsal-fin proximal radial contacting the neural spine of the 10th vertebra (vs. 9th). It further differs from R. schaeferi by having 23-27 mid-dorsal plates (vs. 18-20); 24-28 mid-ventral plates (vs. 20-22); higher caudal peduncle (10.3-13.0% in SL vs. 7.7-8.7); wider head (24.6-28.1% in SL vs. 20.5-23.9%); premaxillary and dentary accessory teeth absent (vs. present). Description. Morphometric and meristic data are given in Tables 3 and 4. Dorsal body profile convex from tip of snout to dorsal-fin origin; concave at dorsal-fin base; straight to caudal-fin origin. Small elevation at supraoccipital immediately posterior to eyes. Ventral head profile slightly concave. Ventral body profile almost straight from pectoral-fin origin to analfin origin, ascending at anal-fin base. Greatest body depth at dorsal-fin origin. Greatest body width at opercular region, gradually tapering toward snout and caudal-fin. Head without longitudinal crests, anterior margin rounded in dorsal view. Snout without rostral plate, bearing numerous small plates with thin odontodes; most anterior portion of head naked. Odontodes equal in size and uniformly distributed, not forming rows, on head and body. Eye small; dorsolaterally placed, not visible in ventral view. Iris operculum present. Infraorbital canal entering infraorbital series via compound pterotic. Compound pterotic roughly quadrangular in shape, without elongate posterior extension, its posteroventral margin with irregular and median to large perforations. Supraoccipital not contributing to the dorsal portion of the swimbladder capsule. Body entirely covered with bony plates, except on ventral Character Frequency distribution Range Mode Dorsal plates right side left side 24(1); 25(1); 26(2); 27(1); 28(1) 25(1); 26(3); 27(1); 28(1) 24-28 26 Mid-dorsal plates right side left side 21(2); 22(2); 23(1); 24(1) 21(2); 22(2); 23(1); 24(1) 21-24 21/22 Median plates right side left side 26(1); 27(2); 28(2); 30(1) 26(1); 27(3); 28(2) 26-30 27 Mid-ventral plates right side left side 22(2); 23(3); 25(1) 22(4); 23(1); 25(1) 22-25 22 Ventral plates rigth side left side 26(1); 27(1); 28(3); 29(1) 24(1); 26(2); 27(2); 29(1) 24-29 26/27/28 Premaxillary teeth right side left side 20(1); 22(1); 23(2); 25(1); 28(1) 19(1); 21(1); 22(1); 24(1); 25(2) 19-28 25 Dentary teeth right side left side 18(1); 19(1); 20(2); 23(1); 24(1) 18(1); 19(1); 20(1); 21(1); 24(1); 25(1) 18-25 20 Dorsal-fin branched rays 6(4); 7(26) 6-7 7 Pectoral-fin branched rays 6 (30) - 30 Pelvic-fin branched rays 5 (30) - 5 Anal-fin branched rays 5 (30) - 5 Caudal-fin branched rays 14(30) - 14 Dorsal procurrent rays 4(2); 5(2) 4-5 - Ventral procurrent rays 4(4) 4 4 Vertebrae 31(4) - 31 Table 2. Frequency distribution of meristics for Rhinolekos britskii (DZSJRP 5614, 6514, 6884, 7018, 7022, 7036, 7042, 12190; MCP 44058; MNRJ 34128; MZUSP 103698). A new genus and three new species of Hypoptopomatinae 72 part of head, region overlying opening of swim bladder capsule and around anus and pelvic-fin origin. Abdomen covered with small plates irregularly arranged. Lips roundish, papillose; lower lip larger than upper lip, with papillae gradually smaller towards edges. Maxillary barbel free from lower lip and reduced. Teeth slender, bifid; median cusp larger and rounded, lateral cusp smaller and pointed. Premaxillary teeth 20-34. Dentary teeth 18-31. Number of teeth increasing with size of specimen. Premaxillary and dentary accessory teeth absent. Dorsal-fin rays ii,6-7; originating at vertical through middle of pelvic fin; its length surpassing anal-fin origin; spinelet small, roughly triangular shaped; locking mechanism non-functional. Anterior portion of compound supraneuralfirst dorsal-fin proximal radial contacting neural spine of 10th vertebra (Fig. 1b). Pectoral-fin rays i,6, originating immediately posterior to opercular opening, surpassing pelvic-fin origin. Cleithrum and coracoid exposed and supporting odontodes only laterally, near pectoral-fin insertion. Arrector fossae partially enclosed by ventral lamina of coracoid; opening relatively large, extending laterally halfway towards pectoral-fin base. Pectoral-fin axillary slit present only in juvenile specimens. Pelvic-fin rays i,4-5, reaching anal-fin origin when depressed. Pectoraland Fig. 5. Rhinolekos garavelloi, holotype, DZSJRP 10479, 31.4 mm SL, male, stream at Fazenda Lageado, rio Paranaíba drainage, Caldas Novas, Goiás State, Brazil. F. O. Martins & F. Langeani 73 pelvic-fin unbranched rays smaller than branched rays; enlarged odontodes at tip of pectoral-fin unbranched ray and at mesial margin of pelvic-fin unbranched ray. Anal-fin rays i,3-5. Caudal-fin rays i,14-15,i; lower lobe slightly longer than upper lobe, in some specimens; four or five dorsal and 3-6 ventral procurrent rays. Adipose fin and azygous plates absent. Median lateral plates 28-32. Median-plate series complete, from compound pterotic to caudal-fin base, absence of canal in one or two plates near region of tenth median plate in some specimens. Vertebrae 32. Color in alcohol. Ground color of dorsal surface light brown; posterior portion of head with transverse dark bar. Trunk with four conspicuous bars: first at dorsal-fin origin; second at end of dorsal-fin base; third at vertical through middle anal fin; last at caudal-fin insertion; less conspicuous in adult specimens. Head darker than remaining portion of dorsum. Clear area between tip of snout and nares. Opercle region unpigmented. Lateral portion of body light brown with dark longitudinal stripe, from compound pterotic to caudal-fin origin. Ventral surface of body mostly unpigmented. Dorsal, anal-, pectoraland pelvic-fins membranes hyaline. Dorsal-fin rays with higher concentration of chromatophores, forming transverse bands. Caudal fin homogeneously dark; tip of lobes unpigmented. Procurrent rays with yellowish white coloration sometimes, extending laterally to caudal peduncle. H Minimum Maximum Mean SD Standard length (mm) 31.4 29.0 36.2 - - Percents of Standard length Predorsal length 50.4 46.6 53.3 49.1 1.5 Preanal length 62.0 57.8 66.0 60.5 1.8 Prepectoral length 27.9 24.4 29.7 27.0 1.2 Prepelvic length 38.3 36.0 42.3 38.5 1.2 Postanal length 30.9 29.0 34.6 31.8 1.3 Thoracic length 20.3 18.1 20.8 19.5 0.8 Abdominal length 22.3 20.6 25.7 23.2 1.2 Caudal-peduncle depth 11.9 10.3 13.0 11.5 0.5 Head length 34.0 29.3 35.3 32.6 1.2 Head width 26.6 24.6 28.1 26.0 0.8 Head depth 16.1 13.2 16.2 15.1 0.6 Base of dorsal-fin length 10.1 9.3 12.6 11.0 0.9 Folded dorsal-fin length 23.4 22.4 25.7 23.5 0.8 Pectoral-fin unbranched ray length 20.1 16.6 21.1 19.4 1.1 Pelvic-fin unbranched ray length 20.2 15.2 21.1 18.7 1.6 Snout-opercle length 28.1 24.7 28.5 26.7 0.8 Percents of Head length Head width 78.3 69.9 87.1 79.7 3.2 Head depth 47.2 40.6 52.3 46.2 2.3 Snout length 51.3 48.5 59.6 52.9 2.6 Orbital diameter 14.3 12.9 16.8 15.1 1.0 Interorbital length 36.4 34.7 42.1 37.3 1.4 Barbel length 8.6 6.5 9.9 8.2 0.7 Prenasal length 32.6 32.5 42.2 35.5 2.1 Internasal length 9.5 9.5 14.4 11.5 1.0 Suborbital depth 26.7 22.3 28.1 25.7 1.5 Table 3. Descriptive morphometrics of Rhinolekos garavelloi. Values given for holotype (H; DZSJRP 10479) and range of 30 specimens (DZSJRP 10477, 12191; MCP 44057; MNRJ 34127; MZUSP 103697); range includes holotype. SD = Standard deviation. Character Frequency distribution Range Mode Dorsal plates right side left side 30(2); 31(1); 32(1); 34(2); 35(1) 31(2); 32(2); 33(1); 34(2) 30-35 34 Mid-dorsal plates right side left side 24(2); 25(3); 26(2) 23(1); 24(2); 25(1); 27(3) 23-27 24/25 Median plates right side left side 29(2); 30(1); 31(2); 32(2) 28(1); 29(1); 30(3); 31(2) 28-32 30/31 Mid-ventral plates right side left side 24(2); 25(4); 28(1) 24(4); 25(1); 27(2) 24-28 24 Ventral plates right side left side 27(1); 28(2); 30(2); 33(1) 27(3); 28(1); 29(1); 32(1) 27-33 27 Premaxillary teeth right side left side 20(1); 24(2); 32(1); 33(1); 34(2) 20(2); 22(1); 30(1); 31(1); 32(1); 33(1) 20-34 20 Dentary teeth right side left side 18(3); 27(1); 28(1); 29(1); 31(1) 19(1); 20(2); 28(2); 29(2) 18-31 18/28/29 Dorsal-fin branched rays 6(9); 7(27) 6-7 7 Pectoral-fin branched rays 6(36) - - Pelvic-fin branched rays 4(1); 5(35) 4-5 5 Anal-fin branched rays 3(1); 4(1); 5(34) 3-5 5 Caudal-fin branched rays 14(33); 15(3) 14-15 14 Dorsal procurrent rays 4(5); 5(1) 4-5 4 Ventral procurrent rays 3(1); 4(2); 5(2); 6(1) 3-6 4/5 Vertebrae 32(5) - 32 Table 4. Frequency distribution of meristics for Rhinolekos garavelloi (DZSJRP 10477, 12191; MCP 44057; MNRJ 34127; MZUSP 103697).