Taxonomic revision of the Rineloricaria species ( Siluriformes : Loricariidae ) from the Paraguay River basin

Species of the genus Rineloricaria from the Paraguay River basin were revised, the following species and geographic distributional patterns were found: R. aurata, Paraguay River basin in Brazil and Paraguay, rio Guaporé in Brazil; R. cacerensis, Paraguay River near Cáceres in Brazil; R. lanceolata, Paraguay River basin in Brazil and Paraguay, Guaporé, Ji-Paraná, Purus, Solimões, and Araguaia rivers in Brazil, Marañón and Madre de Dios rivers in Peru; R. parva, Paraguay River basin in Brazil and Paraguay, Paraná River in Argentina, Uruguay River in Brazil. Loricaria hoehnei is proposed as a new junior synonym of R. lanceolata. A key to the species of Rineloricaria from the Paraguay River basin is provided.


Introduction
The genus Rineloricaria Bleeker, 1862 actually comprises 65 valid species (Ferraris, 2007;Fichberg & Chamon, 2008;Ghazzi, 2008;Ingenito et al., 2008;Rapp Py-Daniel & Fichberg, 2008;Rodriguez & Miquelarena, 2008;Rodriguez & Reis, 2008).Species of this genus exhibit an extensive variation in their body sizes, color pattern, arrangement of abdominal plates, shape of the head, form, and placement of their sexually dimorphic odontodes.Species are found from Panama to central Argentina, including the Chico River in Panama; Atrato, Magdalena, Patía, and Sinú rivers in Colombia; Esmeraldas and Mira rivers in Ecuador; the Atlantic coastal river drainages from northeastern Brazil to the south of Uruguay; and the major tropical rivers of South America, the Orinoco, Amazonas, and La Plata basins.Fichberg & Chamon (2008) diagnosed the genus by the combination of the following characters: postorbital notch present; inferior lip with short rounded papillae; premaxilla with 7 to 15 teeth on each hemiseries; dentary teeth strong, deeply bicuspidate, and larger than premaxillary; coloration of dorsal region with dark-brown bars or blotches; abdomen with a conspicuous polygonal preanal plate, usually bordered by other three large trapezoidal plates.In addition, these authors mentioned as useful some of the following features associated with the sexual dimorphism of mature males: numerous hypertrophied odontodes along the sides of the head and the dorsal surface of pectoral fin in some species (generally thick, short, and curved odontodes); and well-developed odontodes over all of the predorsal area (generally thin, long, and erected or depressed odontodes), sides of head and dorsum of pectoral fin in other members of the genus.
We have revised the following Rineloricaria species: R. aurata, R. cacerensis, R. hoehnei, and R. parva.These species were originally described from the Paraguay River basin and are commonly found from large rivers to small streams throughout this basin, but identities of most of them are problematic considering that they are basically known from their original descriptions, which are at best incomplete.In this paper we contribute to this issue providing new diagnosis, expanding descriptions, and presenting an identification key for the Rineloricaria species described from the Paraguay River basin.

Material and Methods
Counts and measurements were made on the left side of specimens using digital caliper to the nearest 0.1 mm.Methodology follows Isbrücker & Nijssen (1978) excepting postdorsal-and postanal-fin lengths, see below.Measurements of fin spines and counts of thoracic and lateral scutes are according to Isbrücker & Nijssen (1978) but we modified nomenclature as unbranched-fin ray, lateral abdominal plates, and longitudinal lateral plates.The following measurements and counts were added: free maxillary barbel (from its base at lower lip border to its distal tip); prepectoral-, prepelvic-, and preanal-fin lengths (from snout tip to the origin of the anteriormost unbranched-fin ray); postdorsal-, postpectoral-, postpelvic-, and postanal-fin lengths (from origin of anteriormost unbranched-fin ray to base of middle triangular caudal plate); eye diameter (horizontal measurement of eye between its margins, excluding orbital notch); internarial width (distance between nostrils); and posterior plates of the median series (longitudinal plates in the caudal peduncle bearing the sensory canal between two very proximate keels, first counted plate is posterior to the last plate of the mid-ventral series, last counted one is the triangular plate of the caudal fin).Measurements and abdominal plates are shown on Figure 1.
Nomenclature of plates and bones of the head, and of the lateral plate series follows Schaefer (1997).Nomenclature of parieto-supraoccipital follows Arratia & Gayet (1995) and of compound pterotic follows Aquino & Schaefer (2002).
Nomenclature of posterior, median, and anterior abdominal plate complex follows Isbrücker & Nijssen (1979) and are shown on Figure 1.The posterior complex consists of a welldefined preanal plate preceded by three larger polygonal plates, these plates are bordered by five or six small polygonal plates curved in a transversal series that reaches the last lateral abdominal plate.The median complex consists of middle-sized polygonal plates situated between lateral abdominal plates.The anterior complex consists of small polygonal plates situated on the pectoral girdle.
In the species descriptions the values in parentheses indicate the number of specimens with a particular count.In the description of R. cacerensis the numbers indicated by an asterisk are counts of the lectotype.Cleared and stained specimens (c&s) according to Taylor & van Dyke (1985) procedures were used for osteological observations and counts of plates, branchiostegal rays, vertebrae, and ribs.Sexes were characterized after dissecting specimens, or according to the presence of hypertrophied odontodes developed on sides and dorsum of the head, predorsal plates, and dorsum of the pectoral fin of breeding male specimens.
Principal Component Analysis (PCA) was performed using the software PAST (Hammer et al., 2001) in order to detect differences between populations of Rineloricaria lanceolata and R. hoehnei; and differences between R. aurata, R. cacerensis, R. lanceolata, and R. parva.The specimens used in this analysis are indicated in parentheses in the examined material.Samples of R. lanceolata from the upper Amazonas River basin in Perú includes the Huallaga, Urubamba, and Ucayali rivers, samples from the middle Amazonas River and tributaries includes the Solimões, Purus, Madre de Dios, and Guaporé rivers.PCA was performed on the co-variance matrices of log transformed data of the 31 measurements described above; the superior and inferior caudal-fin rays measurements were excluded of the analysis because of having many absent data due damaged specimens.
Institutional acronyms are as listed by Leviton et al. (1985), with the addition of CPUFMT (Coleção de Peixes da Universidade Federal de Mato Grosso, Brazil), CZCEN (Colección Zoológica de la Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Asunción, Paraguay), DZSJRP (Departamento de Zoologia e Botânica, Universidade Estadual Paulista Júlio de Mesquita Filho, Câmpus de São Jose do Rio Preto, Brazil), MZUEL (Museu de Zoologia, Universidade Estadual de Londrina, Brazil), NUP (Coleção Ictiológica do Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá, Brazil), UMSS (Universidad Mayor de San Simón, Bolivia), ZUFMS-PIS (Coleção Zoológica de Referência da Universidade Federal de Mato Grosso do Sul, Brazil).Data of examined and comparative material are given with the species listed alphabetically, type specimens are listed first, and the non-type specimens are ordered as follows (bold format provided only in examined material): Country; Departamento, Estado, or Provincia; collection acronym and catalog number; number of specimens; number of specimens used for morphomeristic analyses in parentheses (provided only for those lots used in measurements, counts, and PCA); size range of specimens examined; and the collecting locality.We indicate if type material was analyzed based on photographs.Type images were downloaded from Museums webpages, or consulting the All Catfish Species Inventory Image Base (Morris et al., 2006).

Results
Principal Component Analysis.Results of the PCA performed with the Rineloricaria hoehnei and R. lanceolata data are shown on Figure 2a and Table 1.The first component has 80.8% of variance and the eigenvectors were all positive; this is interpreted as a general size factor according to Jolicoeur & Mosimann (1960) and graphs including the PC1 axis are not shown.The variance of the second and third components was 4.8% and 3.5%, respectively, and this was interpreted as a variation in the body form following Bookstein (1989).Plots of factor scores for both PC2 and PC3 axes show specimens grouped in a broadly overlapping pattern.The loading variables that contributed most heavily for these axes are highlighted in bold in Table 1.Specimens of R. lanceolata were grouped into three datasets in order to represent populations from the type locality (upper Amazonas in Peru), middle Amazonas River, and Araguaia River.Last two populations encompass the geographical distribution stated for this species by Isbrücker (1973).Plots of the R. hoehnei dataset (Paraguay River basin) overlap the R. lanceolata dataset, especially those from the Guaporé, Purus, and Araguaia rivers.This analysis suggests homogeneous morphology between both species and supports the synonymy of R. hoehnei under R. lanceolata, which is discussed in the description of the latter.Range of variation of the morphometric data in Table 4 also shows overlapping values.PCA performed with the R. aurata, R. cacerensis, R. lanceolata (including Paraguay River specimens), and R. parva data are shown on Figure 2b.Variance of the first, second, and third components are 80.8%, 8.8%, and 2.8%, respectively.Plots of factor scores for both PC2 and PC3 axes show species grouped independently, excepting for R. cacerensis which fall inside set of R. aurata, no ovelapping boundaries among the R. cacerensis, R. lanceolata, and R. parva samples, and a small overlapping pattern of R. aurata with boundaries of R. lanceolata and R. parva.The loading variables that contributed most heavily for these axes are highlighted in bold in Table 1.This analysis suggests morphometric differences between species, especially on axis 2 where R. lanceolata is distinguished from R. parva and R. cacerensis.(Knaack, 2003) Figs.Ribeiro, 1912. -Carvalho & Albert, 2011: 195 [Guaporé River].

Rineloricaria aurata
Diagnosis.Rineloricaria aurata is distinguished from most of its congeners by having four lateral plate series in longitudinal rows below the dorsal fin, the mid-dorsal series absent (Fig. 4a) [vs.five lateral plate series in longitudinal rows below the dorsal fin, the mid-dorsal series present and consisting in two to ten keeled plates situated below the dorsal series and beginning around insertion of the first dorsal-fin ray (Fig. 4b and 4c) in R.  tropeira, and R. zaina]; and by presenting breeding male specimens with sexually dimorphic odontodes on the dorsum of the head and predorsal region (Fig. 3 Snout tip pointed in dorsal view, lateral margins of head straight.Odontodes of head and trunk small, thick, aligned.Dorsum of head rough; pronounced ridges between nostrils on posterior nasal plates to anterior margin of frontals, posterior to eyes on parieto-supraoccipital and compound pterotic; moderate ridges on anterior nasal plates, frontals, sphenotic, and compound pterotic.Infraorbital series with six bones, infraorbital 1 with a sensorial pore exposed ventrally, infraorbitals 2, 3, and 4 convexly raised from anterior portion of snout to eye.Rostral plate with an area without odontodes at tip of snout, narrow, horizontally elongated, short, not surpassing sensorial pore ventrally exposed of infraorbital 1. Posterior margin of parieto-supraoccipital slightly concave to straight, lateral margins truncate.Predorsal plates and first three lateral plates of dorsal series with pronounced ridges or keels.Superior margin of orbit raised, postorbital notch large.Eye large, rounded to slightly oval horizontally. Lower lip narrow, ventral surface covered by short papillae with rounded tip, papillae slightly bigger at line bordering upper lip and close to dentary.Lower lip margin with mediumlengthed fringes; upper lip margin with short fringes.Maxillary barbel long, surpassing distal border of lower lip.Teeth bicuspid, long, mesial cusp greater and wider than lateral, dentary teeth larger than premaxillary.Premaxilla with 6(11), 7(27), 8(4), or 9(1) teeth; dentary with 6(11), 7(36), 8(11),  Body narrow and short, four lateral plate series in longitudinal rows below dorsal fin: dorsal, median, mid-ventral, and ventral; mid-dorsal series absent (Fig. 4a).Median and mid-ventral series with rough well-developed keels; last plate of mid-ventral series extended around end of anal fin.Median series bearing sensory canal between two proximate keels on caudal peduncle.Longitudinal lateral plates 29(2), 30(12), 31(40), 32(19), or 33(2); posterior plates of median series 13(1), 15(12), 16(47), or 17(15).Lateral line complete.Lateral abdominal plates 4(2), 5( 22), 6(45), or 7(6); borders of plates not in contact with lateral plates of mid-ventral series.Lateral region of body posterior to pectoral-fin insertion with a broad area of naked skin between borders of lateral plates of mid-ventral series and of lateral abdominal plates, thickness similar to caudal peduncle width (Fig. 4a).Abdominal plates of posterior complex with a large well-defined preanal plate bordered by three plates and these by five plates.Abdominal plates of median complex parallel and longitudinally arranged in three series posteriorly and in four series anteriorly.Abdominal plates of anterior complex irregular, smaller anteriorly, not projected toward lip; anterior margin convex, reaching horizontal line of anterior margin of cleithrum exposed ventrally.Vertebrae 26(1), 27(8), or 28(2); ribs 4(9) or 5(4).
Color in alcohol.Dorsal surface of body with light or dark brown ground coloration; ventral surface yellow or light brown, ventral plates posterior to pelvic fin with dark brown longitudinal spots forming stripes.Dorsal surface of head from anterior margin of snout to eyes with two longitudinal dark brown stripes.Lateral margins of head with irregular dark brown dots.Posterior region of parieto-supraoccipital with dark brown spot.Pores of sensorial canal of head and lateral line highlighted by black pigments.Dorsal surface of upper lip with two longitudinal light brown stripes, dorsal surface of lower lip with transverse light brown stripe.Dorsal surface of trunk with six narrow, transverse dark brown bands; first at dorsal-fin origin, oblique, extending toward last pectoral-fin ray; second just behind dorsal-fin base, broad, conspicuous; following bands similar, equidistantly separated and sometimes incomplete.Immature specimens about 30 mm SL with pectoral, pelvic, dorsal, and anal fins light brown with dark brown spot on base of first rays, another spot on distal portions of first rays not reaching fin margin, distal spot extending to last ray forming transversal stripe; caudal fin almost totally dark brown except for a light brown blotch on anterior half of four median rays.Specimens about 45 mm SL with pectoral, pelvic, dorsal, and anal fins light brown with irregular dark brown blotches; caudal fin dark brown with narrow light brown band on anterior half.Adult specimens about 70 mm SL with pectoral, pelvic, dorsal, and anal fins light brown with irregular dark brown stripes, first branched rays with small dark brown spot on base and another distally, distal spot usually extended to last ray forming narrow transversal band; caudal fin with small dark brown spot on its base, middle region of branched rays light brown with irregular dark brown stripes, distal portion with broad, transverse, dark brown band, superior and inferior unbranched ray with irregular dark brown dots.See "Remarks" for description of the holotype.
Sexual dimorphism.Dissected females with mature oocytes at about 57 mm SL.Males showing sexually dimorphic odontodes at about 64 mm SL.Breeding male specimens with hypertrophied odontodes arranged on lateral margins and dorsum of head,  predorsal plates, and dorsal region of pectoral-fin rays (Fig. 2); premaxillary and dentary teeth having its mesial cusp enlarged and rounded.Apparently, dimorphic odontodes develop first on lateral margins of head and on dorsum of pectoral fin, and later on dorsum of head and predorsal plates.Dimorphic odontodes on dorsum of head and predorsal region straight, thin, long, depressed, usually covered by skin at base, sometimes entirely covered, distributed in a large area over frontal, sphenotic, compound pterotic, parieto-supraoccipital, and predorsal plates.Dimorphic odontodes on lateral margins of head thin and long, tips hook-like curved, usually covered by skin at base, distributed over suprarostral plates, postrostral plates 2, 3, 4, subocular cheek plates 1, 2, and opercle.Dimorphic odontodes on dorsal region of pectoral branched rays thin, long, curved medially, distributed over almost entire portion of first to fifth rays and usually covered by skin at base; dimorphic odontodes of unbranched rays shorter and more densely arranged.

Distribution and habitat.
Rineloricaria aurata is known from the Paraguay River basin in Paraguay and Brazil, and from the Guaporé River in Brazil (Fig. 5).In Paraguay, this species were Remarks.Knaack (2003) mentioned in the abstract of the original description of Rineloricaria aurata that a uniquely colored mailed catfish is described.This color pattern was characterized by a remarkably gold coloring of body dorsally and ventrally; black stains on dorsal-, pectoral-, ventral-, and anal-fin distal margins; a rounded black spot on the inferior lobe of the caudal fin; and irregular black marks before and below dorsal-fin insertion.The author stated that specimens changed their luminous intensity and mark designs according to environmental alterations of the aquarium and behavior condition, except for a black blotch posterior to the right eye in the holotype.In the preserved holotype, the black spot below right eye is still visible, marks on dorsal and pectoral fins are badly visible, marks before and below dorsal-fin insertion are brown reddish, and marks on nostrils, ventral, anal, and caudal fins are missing (Fig. 6).We conclude that the author was based in peculiarities of the color pattern of one abnormal specimen to diagnose this species, which was preserved as the holotype and the unique type specimen.See "Discussion" for more details.
Examined material.Type specimens: ZMA 123591, holotype, 83.0 mm SL, río Aquidaban, Dpto.de Concepcion, Strecke Loreto-San Carlos, Paraguay.Non-type specimens: Brazil: Mato Grosso State: CPUFMT 301,11,CPUFMT 302,5,CPUFMT 303,7,    Description.Morphometric data presented in Table 3. Snout tip raised in lateral view.Dorsal profile from snout tip to posterior nasal plates straight, convex from frontals to nuchal plate, declined at dorsal-fin base, straight from end of dorsalfin base to penultimate dorsal plate, caudal fin damaged on three syntypes.Ventral profile from snout tip to anal-fin base convex, straight from that point to penultimate ventral plate, caudal fin damaged on three syntypes.Snout tip pointed in dorsal view, lateral margins of head curved anteriorly.Odontodes of head and trunk small, thick, aligned.Dorsum of head smooth, without ridges.Infraorbital series with six bones, infraorbital 1 with a sensorial pore exposed ventrally, infraorbitals 2, 3, and 4 convexly raised from anterior portion of snout to eye.Rostral plate with an area of naked skin without odontodes at tip of snout, narrow, horizontally elongated, short, not reaching sensorial pore ventrally exposed of infraorbital 1. Posterior margin of parietosupraoccipital slightly concave to straight, lateral margins truncate.Predorsal plates and first three lateral plates of dorsal series with ridges or keels moderately developed.Superior margin of orbit slightly raised, postorbital notch large.Eye large, rounded to slightly oval horizontally.
Body narrow and long, five lateral plate series in longitudinal rows below the dorsal fin: dorsal, mid-dorsal, median, mid-ventral, and ventral.Mid-dorsal series with moderately-developed keels, last plate extended around end of dorsal fin.Median and mid-ventral series with rough welldeveloped keels, last plate of mid-ventral series extended around end of anal fin.Median series bearing sensory canal between two proximate keels on caudal peduncle.Longitudinal lateral plates 30(1) or 31*(2); posterior plates of median series 15(1) or 16*(2).Lateral line complete.Lateral abdominal plates 6*(46).Lateral region of body posterior to pectoral-fin insertion between borders of lateral plates of mid-ventral series and of lateral abdominal plates with a slender area of naked skin, narrower than caudal peduncle width.Abdominal plates of posterior complex with a large well-defined preanal plate bordered by three plates and these by five plates.Abdominal plates of median complex parallel and longitudinally arranged in three series posteriorly and increasing series anteriorly.Abdominal plates of anterior complex irregular, smaller anteriorly, projected toward lip; anterior margin convex, surpassing horizontal line of anterior margin of cleithrum exposed ventrally.
Color in alcohol.Based on lectotype and two paralectotypes, which are poorly preserved (color of specimens as originally described on "Remarks").Dorsal surface of body with dark brown ground coloration; same coloring on ventral surface.Dorsal surface of head from anterior margin of snout to last dorsal plate with large and irregular dark brown spots in lectotype, small and irregular spots visible only on head in paralectotypes.Dorsal and pectoral fins with dark brown bars on rays, pectoral-fin membranes with dark brown pigments, caudal fin uniformly dark brown pigmented on branched rays and membranes, unbranched rays pale brown.

Sexual dimorphism. No sexual dimorphism is known.
Distribution and habitat.Rineloricaria cacerensis is known from its type locality, Cáceres, Mato Grosso State, Brazil (Paraguay River basin).See additional comments on Discussion.
Remarks.The lectotype and paralectotypes of Rineloricaria cacerensis are highly discolored, with the caudal fin partly damaged not allowing confirmation of some characters related to caudal-fin filaments and color pattern mentioned in the original description of Miranda Ribeiro (1912).The caudal fin was described with the external rays prolonged as in R. parva, but with the superior one much longer.The dorsal overall ground coloration was described as light brown (pardo barrento); with a stripe on head around eyes; a blotch on predorsal region (triângulo cervical); five black transversal bands, the first around dorsal-fin insertion, the second broader and located posteriorly to dorsal fin, the remaining three equidistantly on caudal peduncle; caudal fin black, excepting outer rays; and dorsum of body from dorsal-fin end to penultimate dorsal plate, elevated from last dorsal plate to end of caudal fin.Ventral profile from snout tip to anal-fin base convex, straight from that point to penultimate ventral plate, declined from last ventral plate to end of caudal fin.Snout tip rounded in dorsal view, lateral margins of head straight.Odontodes of head and trunk small, thick, not aligned.Dorsum of head slightly rough; parieto-supraoccipital with indistinct ridges.Infraorbital series with six bones, infraorbital 1 with a sensorial pore exposed ventrally, infraorbitals 2, 3, and 4 not raised.Rostral plate with an area of naked skin without odontodes at tip of snout, narrow, horizontally elongated, very short, not reaching sensorial pore ventrally exposed of infraorbital 1. Posterior margin of parietosupraoccipital slightly concave to straight; lateral margins truncate.Predorsal plates and first three lateral plates of dorsal series with ridges or keels moderately developed.Superior margin of orbit not raised; postorbital notch small.Eye small, rounded to slightly oval horizontally.
Body wide and short, four lateral plate series in longitudinal rows below dorsal fin: dorsal, median, mid-ventral and ventral; mid-dorsal series absent.Median and mid-ventral series with rough well-developed keels; last plate of mid-ventral series extended around end of anal fin.Median series bearing sensory canal between two proximate keels on caudal peduncle.Longitudinal lateral plates 29(3), 30(36), 31(53), 32(11), or 33(1); posterior plates of median series 13(3), 14 (26), 15(36), 16(33), or 17(6).Lateral line complete.Lateral abdominal plates 5 (6), 6(23), 7(49), 8(20), or 9(6), borders of plates not in contact with lateral plates of mid-ventral series.Lateral region of body posterior to pectoral-fin insertion with a broad area of naked skin, thickness similar to caudal peduncle width, situated along borders of lateral plates of mid-ventral series and of lateral abdominal plates (as shown on Fig. 4a).Abdominal plates of posterior complex with a large welldefined preanal plate bordered by three plates and these by five plates, sometimes divided in smaller plates.Abdominal plates of median complex parallel and longitudinally arranged in three series increasing in number toward anterior complex.
Color in alcohol.Dark brown or black dots over dorsal suface of body; overall ground coloration light or dark brown; ventral surface light brown.Sometimes clearer ground coloration of anterior region of body with many small dark dots, posterior region of dorsal surface totally black, and abdominal region with irregular dark brown blotches.Dorsal surface of head and predorsal region with two longitudinal dark brown to black bands, running from snout tip through eyes and second predorsal plate; narrow dark brown or black stripes running parallel and below former bands from snout tip to eyes.Lateral margins of head between infraorbital 4 and subocular cheek plate 1 with dark brown or black stripe; opercle and compound pterotic with irregular dark brown or black dots.Pores of sensorial canal of head and anterior lateral line highlighted by black pigments.Dorsal surface of upper lip with two longitudinal brown stripes, dorsal surface of lower lip with a transverse brown stripe.Dorsal surface of trunk with four to six wide, transverse, dark brown or black bands; first at dorsalfin origin, oblique, extending toward last pectoral-fin ray; second just behind dorsal-fin base; following bands similar, equidistantly separated and lighter.All unbranched fin rays light or dark brown with narrow dark brown or black stripes.Pectoral, pelvic, dorsal, and anal fins with broad longitudinal dark brown or black band running parallel to first two or three rays; last rays with narrow, transverse, dark brown or black stripe on their middle length leaving hyaline areas on extremities.Sometimes, all fins black with narrow hyaline distal area on last rays.Caudal fin with longitudinal, dark brown or black band on first and last three branched rays; light brown area on four median rays usually with irregular dark stripes.
Sexual dimorphism.Dissected females with mature oocytes at about 77 mm SL.Males showing sexually dimorphic odontodes at about 71 mm SL.Breeding male specimens with hypertrophied odontodes arranged on lateral margins and dorsum of head, predorsal plates, and dorsal region of pectoral-fin rays (Fig. 8); premaxillary and dentary teeth having its mesial cusp enlarged and rounded.Apparently, dimorphic odontodes develop first on lateral margins of head and on dorsum of pectoral fin, and later on dorsum of head and predorsal plates.Dimorphic odontodes on dorsum of head and predorsal region straight, thin, long, depressed, usually covered by skin at base, sometimes entirely covered, distributed in a large area over frontal, sphenotic, compound pterotic, parieto-supraoccipital, and predorsal plates.Dimorphic odontodes on lateral margins of head thin and long, tips hook-like curved, usually covered by skin at base, distributed in a large area below sensorial canal of infraorbital series over suprarostral plates, infraorbital 1, postrostral plates 2, 3, 4, subocular cheek plates 1, 2, and opercle.Dimorphic odontodes on dorsal region of pectoral branched rays thin, long, curved medially, covering almost entire portion of first to fifth rays and usually covered by skin at base; dimorphic odontodes over unbranched ray shorter and more densely arranged.
Distribution and habitat.Rineloricaria lanceolata is known from the Amazonas (including the rios Madeira and Purus); the Paraguay; and the Araguaia river basins (Fig. 9).Specimens from the Branco River in Guyana were also reported in Isbrücker (1973).Specimens of R. lanceolata were collected together with specimens of R. aurata and Farlowella paraguayensis along of the Jejuí and the Piribebuy drainages (Paraguay River basin in Paraguay) associated to leaves of partially submerged plants in small streams of clear and running waters.extended laterally and surpass the sensorial pore ventrally exposed of the infraorbital 1 [vs.tip of the snout pointed; five to seven longitudinal series of abdominal plates on the median complex; tip of the snout with a narrow and short area of naked skin at the rostral plate, which does not surpass the sensorial pore ventrally exposed of the infraorbital 1].
Description.Morphometric data presented in Table 5. Snout tip straight in lateral view, not raised.Dorsal profile from snout tip to frontals straight, elevated from this point to nuchal plate, declined from dorsal-fin origin to penultimate dorsal plate, elevated from last dorsal plate to posterior end of caudal fin.Ventral profile from snout tip to anal-fin base convex, straight from that point to penultimate ventral plate, declined from last ventral plate to end of caudal fin.Snout tip rounded in dorsal view, lateral margins of head straight.Odontodes of head and trunk small, thick, aligned forming striae, more evident between nostrils and on region posterior to eyes.Infraorbital series with six bones, infraorbital 1 with a sensorial pore exposed ventrally, infraorbitals 2, 3, and 4 convexly raised from anterior portion of snout to eye.Rostral plate with an area of naked skin without odontodes at tip of the snout, wide and long, laterally extended, surpassing the sensorial pore ventrally exposed of infraorbital 1 and reaching horizontal line through margin of upper lip.Posterior margin of parieto-supraoccipital concave, sometimes pointed with lateral margins convex.Parieto-supraoccipital and predorsal plates smooth, without ridges, or with ridges very low.First three lateral plates of dorsal series with moderatelydeveloped ridges or keels.Superior margin of orbit low or slightly raised, postorbital notch small to medium.Eye large, rounded to slightly oval horizontally, iris rounded, olive, pupil vertically oval, black.
Color in alcohol.Dorsal surface of body light to dark brown overall ground coloration, ventral surface yellowish brown, ventral plates posterior to pelvic fin with dark brown blotches.Dorsal surface of head from anterior margin of snout to eyes with two longitudinal dark brown stripes.Lateral margins of head from infraorbital 4 to subocular cheek plate 1 with a transversal dark brown band; irregular dark brown blotches on postrostral plates, subocular cheek plates 1 and 2, opercle, and cleithrum.Sphenotic and parieto-supraoccipital with narrow dark brown stripe.Pores of sensorial canal of head and predorsal region highlighted by black pigments.Dorsal fin insertion with a slender area of naked skin, narrower than the caudal peduncle width (Fig. 4b and 4c); tip of the snout with a wide naked area without odontodes on the rostral plate, which is extended laterally and surpass the sensorial pore ventrally exposed of the infraorbital 1; pectoral, dorsal, pelvic, and anal fins with the unbranched ray conspicuously longer than the branched rays; breeding male specimens with short hypertrophied sexually dimorphic odontodes developed only on the sides of the head and on dorsum of the pectoral fin, not developed on the dorsum of the head and predorsal plates (Fig. 12) ……………………………....................... Rineloricaria parva 2b.Lateral region of the body just posterior to the pectoralfin insertion with a broad area of naked skin, similar in thickness to the caudal peduncle width (Fig. 4a); tip of the snout with a narrow and short naked area without odontodes on the rostral plate, which does not surpass the sensorial pore ventrally exposed of the infraorbital 1; dorsal, pectoral, pelvic, and anal fins with the unbranched ray not much longer than the branched rays; breeding male specimens with long hypertrophied sexually dimorphic odontodes developed on the sides of the head, dorsum of the head and predorsal plates, and dorsum of the pectoral fin (Figs. 3 and 8) ……………………....…………………… 3 3a.Dorsum of the head rough, with pronounced ridges from nasal plates to the interorbital region; pectoral and dorsal fins with irregular dark stripes over rays, a dark spot on base of first branched rays and another distally, caudal fin with a transversal dark band on distal region; tip of the snout pointed in a dorsal view ……… Rineloricaria aurata 3b.Dorsum of the head slightly rough, without ridges between nostrils and interorbital region; pectoral, dorsal, and caudal fins with a broad longitudinal dark band running parallel to the first rays; tip of the snout rounded in a dorsal view …………………………………...... Rineloricaria lanceolata

Discussion
Rineloricaria aurata was only known from the holotype.The species was described by Knaack (2003) based on three specimens captured in the Aquidabán River, Paraguay.Those specimens were collected in an expedition for aquarium trade, kept alive, and exported to Germany.The author preserved only one exemplar as the type specimen (ZMA 123591, holotype, Fig. 6); the other two specimens were kept alive for reproduction purposes and were not deposited in a museum.In the original description the author did not present a diagnosis for this species but mentioned in the abstract that a uniquely colored mailed catfish is described.A description of the coloration of the holotype is on the Remarks section of the R. aurata description; see above.During this revision we have examined numerous museum records from the Paraguay River basin in Paraguay that revealed no specimen with the same color pattern, including material from the type locality and other localities of the Aquidabán River basin.We conclude that the specimens used in the original description are anomalous, perhaps xanthic forms.The extremely yellow to orange coloration, or gold pattern as described, and the irregular black markings on body (which are not bilaterally symetrical, and with individual differences between the three specimens as stated in the original description) strongly suggest this.Like albino or melanin phenotypes, xanthochromism can be expressed partially or totally, and the specimen described by Knaack seems to represent a partial xanthic form.
Rineloricaria cacerensis is currently only known from the lectotype and two paralectotypes.This species is very similar to R. melini in the coloration pattern, and similar to other species as R. fallax, R. formosa, R. hasemani, R. jubata, R. melini, R. morrowi, and R. teffeana in the overall morphology.However, we can not be conclusive of his status without a taxonomic revision of the above cited Amazonian species, and this is outside the scope of this paper.We encourage further investigations on R. cacerensis with the inclusion of these similar forms, especially because the diagnostic differences mentioned here for this species are mainly coloration characters based only on its original description and examination of the three types, which are clearly juvenile specimens.We decided to maintain this species as valid and provide a tentative diagnosis, description, photographs, and measurements of the type specimens to help to define its taxonomic status.Noteworthy, despite the large amount of specimens analyzed from the Paraguay River basin during this revision we did not found more specimens of R. cacerensis beside the type series.This lack of material could be due to insufficient collecting efforts, a geographical distribution restricted merely to the upper portions of the Paraguay River near Cáceres, or a mistake when cataloging type locality; however, discarding any of these alternatives is difficult.
Rineloricaria hoehnei (Miranda Ribeiro, 1912) was described based on a single immature specimen of 46.8 mm SL collected in the city of Coxim (drainage of the rio Taquari , Paraguay River basin), Mato Grosso do Sul State, Brazil.This species is commonly cited in catalogs or manuals, but it is just known from its original description and holotype (Ferraris, 2003;Britski et al., 2007;Ghazzi & Oyakawa, 2007).We analyzed the holotype (Fig. 10) and concluded that the color pattern of the fins, snout form, plate arrangements and counts correspond to typical characters of R. lanceolata.Indeed, we did not find any diagnostic differences between R. hoehnei specimens from the whole Paraguay River basin (usually identified as R. lanceolata) and several R. lanceolata specimens from the Amazonas River basin [including the río Marañón in Peru (type locality), as well as Madre de Dios, Guaporé, Ji-Paraná, Purus, and Solimões rivers] and the rio Araguaia basin by analyzing external morphology and osteological counts.Our analysis including the PCA detailed above evidenced that specimens from those basins exhibit similar morphometric values, color pattern, and shape of the snout and body (Table 1, Fig. 1a).Consequently, R. hoehnei is herein considered as a junior synonym of R. lanceolata because it is the older name available according to the Article 23 of the ICZN (1999).In this revision, we examined specimens from the Amazonas and Araguaia river basins corroborating the wide geographical distribution of R. lanceolata as previously described by Isbrücker (1973), and we expand the distribution range of this species to the Paraguay River basin.

Fig. 4 .
Fig. 4. Lateral plate series in three Rineloricaria species: a) R. aurata, b) R. eigenmanni, c) R. hasemani.See also the region posterior to the pectoral-fin insertion, which shows a broad area of naked skin in the Fig. 4a, and a slender area in Figs.4b and 4c.P = Pectoral-fin insertion, LAP = Lateral abdominal plates.

R
. hasemani, R. jubata, R. melini, R. morrowi, R. osvaldoi, R. teffeana, and R. zaina, by having the lateral plate of the middorsal series consisting in five to seven keeled plates extended posteriorly around end of the dorsal-fin base (Fig.4c) [vs.lateral plate of the mid-dorsal series consisting in two keeled plates situated around insertion of first ray of the dorsal fin (Fig.4b) in R. altipinnis, R.caracasensis, R. eigenmanni, R. heteroptera, R. konopickyi, R. phoxocephala, R. platyura, and R. steindachneri].It is distinguished from R. daraha, R. osvaldoi, and R. zaina by having three longitudinal series of abdominal plates on the median complex (vs.several unorganized abdominal plates on the median complex in R. daraha; five longitudinal series of abdominal plates on the median complex in R. osvaldoi and R. zaina).It is distinguished from R. fallax, R. formosa, R. hasemani, R. jubata, R. melini, R. morrowi, and R. teffeana by the caudal fin coloring, consisting in a plain dark brown caudal fin on branched rays and membranes, and a barred superior and inferior unbranched rays (vs.caudal fin excepting outer unbranched rays with a small black stain at its base followed by a broad light-colored area with dark bars on rays and a terminal black margin in R. hasemani, R. jubata, R. melini, R. morrowi, and R. teffeana; caudal fin dark brown with vertical darker bars on rays in R. fallax and R. formosa).It is further distinguished from R. fallax, R. formosa, R. hasemani, R. jubata, R. morrowi, and R. teffeana by having the dorsum of body with large irregular spots (vs.dorsum with a single predorsal spot in R. fallax; dorsum with small spots in R. formosa and R. morrowi; and dorsum without spots in R. hasemani, R. jubata, and R. teffeana); and from R. melini by having the dorsum of head without dark cross bars (vs.head with four dark cross bars).

Table 1 .
or Variable loadings for the Principal Component Analysis, the modular higher eigenvectors of Principal Component axes 2 and 3 are shown in bold.

Table 5 .
Heckman (1998)3) Rineloricaria parva.n=Number of specimens, SD = Standard deviation.Rineloricaria parva is distributed in the Paraguay River basin in Brazil and Paraguay, Paraná River in Argentina, and Uruguay River in Brazil (Fig.13).Additional records of R. parva fromRodriguez (2003)indicated that this species is distributed along the whole Paraná River in Argentina (from region of Esteros del Iberá in Provincia de Corrientes to the mouth of the Paraná River in Provincia de Buenos Aires) and the Uruguay River in Argentina (a single record from Concordia, Provincia de Entre Ríos).Therefore, its distribution encompasses the main rivers of the La Plata River basin, except Paraná River upstream from the Yacyretá Hydroelectric Dam and the upper Paraná River in Brazil.In Paraguay, specimens of R. parva were captured in the Paraguay River margins associated to floating macrophyte banks.Most specimens examined in this revision were collected in large rivers but seem to have been poorly sampled in streams.Heckman (1998)cited this species in the Brazilian Pantanal where it is abundant in roots of floating macrophytes (usually plants of the genus Salvinia).