Rineloricaria parva ( Boulenger, 1895 )

Vera-Alcaraz, Héctor S., Pavanelli, Carla S. & Zawadzki, Cláudio H., 2012, Taxonomic revision of the Rineloricaria species (Siluriformes: Loricariidae) from the Paraguay River basin, Neotropical Ichthyology 10 (2), pp. 285-311 : 302-307

Rineloricaria parva ( Boulenger, 1895) Figs. 11 , 12 and 13

Loricaria parva Boulenger, 1895: 527 [original description; type locality: Paraguay River, Descalvados, Mato Grosso State, Brazil]. - Boulenger, 1896: 32 [transcription of the original description; drawing of the body in lateral, dorsal and ventral views]. - Eigenmann et al., 1907: 121 [listed; Corumbá in Brazil, and near Asunción in Paraguay]. - Eigenmann, 1909: 342 [listed; Paraguay River]. - Miranda Ribeiro, 1911: 125, fig. 68 [key to species; translation of the original description to Portuguese and reproduction of the figure of Boulenger, 1896]. - Miranda Ribeiro, 1912: 10 [listed; Paraguay River at Cáceres, Brazil]. - Fowler, 1932: 370 [drawing (inferior figure of page 364); description; upper Paraguay River in Brazil].

Loricaria Rhineloricaria [sic] parva . - Regan, 1904: 276 [listed; La Plata River basin; key of species; description]. - Eigenmann, 1910: 413 [listed; Paraguay River]. - Ringuelet et al., 1967: 410 [key of species; description; biological data; Paraná River in Argentina and Paraguay River in Brazil].

Rineloricaria parva . - Fowler, 1954: 119 [listed; Paraguay River]. - Isbrücker & Nijssen, 1976: 111 [listed]. -Isbrücker, 1978: 112 [coments about generic status; lectotype designation: BMNH 1895.5.17.91). - Britski et al., 1999: 131 [listed; synopsis of the original description; drawing]. - Chernoff et al., 2001: 146 [listed; Paraguay River in Paraguay]. - Rodriguez, 2001: 169, fig. 1-4 [sexual dimorphism; comparative pictures of male and female specimens; drawn of teeth]. - Ferraris, 2003: 343 [listed; Paraguay River in Argentina and Brazil]. -Vera & Castillo, 2006: 56 [listed; Paraguay River in Paraguay]. - Britski et al., 2007: 160 [listed; synopsis of the original description; drawing]. - Ghazzi & Oyakawa, 2007: 91 [listed; Paraguay River in Brazil].

Hemiloricaria parva . - Isbrücker et al., 2001: 23 [listed]. - Isbrücker, 2001:27 [listed]. - López et al., 2003: 45 [listed; Paraná-Paraguay River basin]. - Menni, 2004: 81, 95 [listed; Paraná-Paraguay River basin]. - Ferraris, 2007: 246: [listed; Paraguay River in Argentina and Brazil].

Diagnosis. Rineloricaria parva 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. aequalicuspis , R. altipinnis , R. anhanguapitan , R. anitae , R. baliola , R. cacerensis , R. capitonia , R. caracasensis , R. daraha , R. eigenmanni , R. fallax , R. formosa , R. hasemani , R. heteroptera , R. isaaci , R. jaraguensis , R. jubata , R. konopickyi , R. kronei , R. latirostris , R. maacki , R. malabarbai , R. maquinensis , R. melini , R. microlepidogaster , R. morrowi , R. osvaldoi , R. pentamaculata , R. phoxocephala , R. platyura , R. reisi , R. rupestris , R. steindachneri , R. stewarti , R. teffeana , R. tropeira , and R. zaina ]. It is distinguished from remaining members of the genus, except R. castroi and R. wolfei , by presenting the caudal fin with both unbranched rays extended as long filaments ( Fig. 11 ) [vs. caudal fin with both unbranched rays not prolonged as filaments or with only the superior unbranched ray extended as a filament in R. aurata , R. beni , R. cadeae , R. catamarcensis , R. felipponei , R. lanceolata , R. langei , R. lima , R. longicauda , R. magdalenae , R. misionera , R. nigricauda , R. pareiacantha , R. quadrensis , R. sanga , R. setepovos , R. sneiderni , R. stellata , R. strigilata , R. thrissoceps , and R. uracantha ]. It is distinguished from R. castroi and R. wolfei by having the tip of the snout rounded in a dorsal view; three longitudinal series of abdominal plates on the median complex; and the tip of the snout with a wide and long area of naked skin without odontodes at the rostral plate, which is 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 moderately-developed 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.

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 margins with very short fringes ( Fig. 12c ); upper lip margin with shorter fringes. Maxillary barbel long, longer than orbital diameter, surpassing distal margin of lower lip and almost reaching ventral border of the subocular cheek plate 1. Teeth bicuspid, long, mesial cusp greater and wider than lateral, dentary teeth larger than premaxillary.Premaxilla with 7(4), 8(33), 9(15), 10(14), or 11(1) teeth; dentary with 7(4), 8(28), 9(24), or 10(16) teeth. Sexual dimorphism on teeth present (see sexual dimorphism). Branchiostegal rays 4(7).

Body narrow and long, 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(14), 30(48), 31(13), or 32(2); posterior plates of median series 15(21), 16(50), or 17(6). Lateral line complete. Lateral abdominal plates 5(17), 6(32), 7(24), or 8(4); borders of plates in contact with lateral plates of mid-ventral series. Lateral region of body posterior to pectoral-fin insertion with a slender area of naked skin between borders of lateral plates of mid-ventral series and of lateral abdominal plates, 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, sometimes divided in smaller plates. Abdominal plates of median complex parallel and longitudinally arranged in three series.Abdominal plates of anterior complex irregular, smaller than other plates, not projected toward lip; anterior margin convex, slightly surpassing horizontal line of anterior margin of cleithrum exposed ventrally. Vertebrae 25(1), 26(7), or 27(1); ribs 4(9).

Dorsal fin ii,6(2); ii,7(74); or ii,8(1); dorsal-fin spinelet present, locking mechanism not functional; unbranched ray conspicuously longer than branched rays, depressed unbranched ray reaching eight plate posterior to its base, last branched ray reaching fourth plate; distal margin truncate. Pectoral fin i,6(77); unbranched ray conspicuously longer than branched rays, depressed unbranched ray reaching almost half pelvic-fin length; distal margin truncate. Pelvic fin i,5(77); unbranched ray evidently longer than branched rays, depressed unbranched ray and two following branched rays reaching beyond anal-fin origin; distal margin truncate. Anal fin i,5(77); unbranched ray evidently longer than branched rays, depressed unbranched ray reaching sixth plate posterior to its base; depressed last branched ray reaching fourth plate; distal margin truncate. Caudal fin emarginated, i,9,i(1) or i,10,i(74); superior and inferior unbranched rays extended as long filaments similar in length to each other.

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 surface of upper and lower lip with two longitudinal dark brown stripes. Dorsal surface of trunk with six transversal dark brown bands; first band at base of origin of first rays of dorsal fin, oblique, extending toward last pectoral-fin ray; second just behind dorsal-fin base; following bands similar, equidistantly separated. Some specimens about 50 mm SL with a narrow and inconspicuous band on parieto-supraoccipital.All fin rays light brown with dark brown stripes. Pectoral, pelvic, dorsal, and anal fins with dark brown blotches on distal portion of rays, forming narrow transversal stripe not reaching fin margin; caudal-fin base with narrow dark brown spot, distal region with dark brown transversal stripe. Caudal fin of specimens about 45 mm SL with large transversal distal band from middle of rays to distal margin; specimens about 60-75 mm SL with moderately large transversal dark brown band on its distal margin; specimens about 80 mm SL with narrower, distal, transverse, dark brown band.

Sexual dimorphism. Dissected females with mature oocytes at about 93 mm SL. Males showing sexually dimorphic odontodes at about 80 mm SL. Breeding male specimens with premaxillary and dentary teeth having its mesial cusp enlarged and rounded. Arrangement and form of dimorphic odontodes different from those described to Rineloricaria aurata and R. lanceolata in the anterior section, to R. fallax on Steindachner (1915), and to R. heteroptera in Isbrücker & Nijssen (1976). Breeding male specimens with dimorphic odontodes arranged on lateral margins of head and on dorsal surface of pectoral-fin rays, absent on dorsum of head and predorsal plates ( Fig. 12 ). Dimorphic odontodes on lateral margin of head short, not covered by skin, tips hook-like curved, distributed in an area much narrower than those in R. aurata and R. lanceolata over postrostral plates 2, 3, 4, subocular cheek plates 1, 2, and opercle, lacking on suprarostral plates. Dimorphic odontodes on dorsal region of pectoral branched rays short, curved medially, covered by skin at base, distributed over almost entire portion of first to fifth branched rays; dimorphic odontodes on unbranched ray slightly shorter and more densely arranged.

Distribution and habitat. 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 from Rodriguez (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 ).

Examined material. Type specimens: BMNH 1895.5 .17.91, photograph of lectotype, Descalvados, Mato Grosso, Brazil. Non-type specimens: Argentina: Provincia de Santa Fé : MCP 40426 , 13 of 23, (3), 61.5-86.5 mm SL, rio Paraná , Santa Fé . Brazil: Mato Grosso State: MCP 15703 , 5 , (2), 60.0- 95.6 mm SL, rio Paraguai, Cáceres . MCP 15728 , 1 of 2, (1), 76.7 mm SL, rio Bugres, Barra do Bugres . MCP 36517 , 1 , 86.4 mm SL, stream of the Poconé Pantanal, Poconé . MCP 36518 , 9 , 45.1-58.3 mm SL, unspecified stream ( Paraguay River basin), Poconé . MCP 36519 , 1 , (1), 75.8 mm SL, riacho Caramujo, Cáceres . MCP 40425 , 2 , 67.0- 67.8 mm SL, pool at the Poconé Pantanal, Poconé . MNRJ 21861 , 2 , 41.1-47.1 mm SL, locality not specified ( Paraguay River basin), Poconé . MZUEL 3518 , 45 , 45.5- 67.1 mm SL, stream affluent of the rio Pixaim, Poconé . MZUEL 5020 , 12 , (6), 84.0- 96.9 mm SL, stream affluent of the rio Pixaim, Poconé . MZUEL 5157 , 3 , 31.3-48.5 mm SL, pond near rio Corixo, Poconé . MZUEL 5160 , 1 , 94.1 mm SL, stream affluent of the rio Pixaim, Poconé . MZUEL 5161 , 14 , 33.6-88.8 mm SL, stream near rio Pixaim, Poconé . MZUSP 19253 , 1 , (1), 86.6 mm SL, locality not specified ( Paraguay River basin), Poconé . MZUSP 44410 , 7 , (1), 48.0- 69.9 mm SL, rio Paraguai, Cáceres . MZUSP 44428 , 1 , 63.4 mm SL, riacho Caramujo, Cáceres . NUP 3427 , 3 , (2), 75.6-82.1 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4144 , 1 , (1), 71.5 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4365 , 14 , 54.1-80.1 mm SL, baía Caiçaras, Cáceres . NUP 4416 , 4 , (3), 57.2-73.9 mm SL, córrego Cancela, Nobres . NUP 4646 , 3 , (1), 65.50-85.70 mm SL, baía Sinhá Mariana ( Paraguay River basin), Barão de Melgaço . NUP 4647 , 2 , (1), 58.2-78.0 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4648 , 2 , 58.9-64.8 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4649 , 1 c&s, 64.8 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4650 , 3 , 56.9-71.7 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4651 , 4 , (1), 63.3-79.7 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 4652 , 4 , (1), 63.1-75.0 mm SL, baía Sinhá Mariana, Barão de Melgaço . NUP 6121 , 1 c&s, 88.3 mm SL, baía Sinhá Mariana, Barão de Melgaço. Mato Grosso do Sul State : DZSJRP 2270, 21, 57.44-98.55 mm SL (1 specimen with the caudal fin regenerated), rio Miranda, Miranda . MZUEL 5152 , 2 , 96.4-111.3 mm SL, stream affluent of the rio Miranda, Corumbá . MZUEL 5153 , 2 , 58.3-64.7 mm SL, riacho Passo da Lontra, Corumbá . MZUEL 5155 , 1 , 85.1 mm SL, baía da Medalha in rio Miranda, Corumbá . MZUEL 5156 , 1 , 79.4 mm SL, Porto da Manga at rio Paraguai, Corumbá . MZUSP 36329 , 3 , (1), 64.0-96.0 mm SL (1 specimen with the caudal fin regenerated), Santa Branca Farm, Nhecolandia . MZUSP 49957 , 1 , 98.8 mm SL, baía Albuquerque, Corumbá . MZUSP 59350 , 6 (plus 6 ex. of R. aurata ), 53.1-68.7 mm SL, riacho Santo Antônio, Aquidauana . MZUSP 59368 , 1 (plus 1 ex. of R. aurata ), 69.8 mm SL, rio Abobral 3, Corumbá . MZUSP 59369 , 1 (plus 1 ex. of R. aurata ), 46.3 mm SL, rio do Peixe, Corumbá . MZUSP 60010 , 20 of 46, (1), 45.2-80.7 mm SL, rio Vermelho, Corumbá . NUP 202 , 8 , (4), 81.85-94.0 mm SL, rio Paraguai, Corumbá . NUP 4759 , 6 , 74.9-79.8 mm SL, channel at Transpantaneira road, Corumbá . NUP 6120 , 1 c&s, 86.1 mm SL, rio Paraguai, Corumbá . ZUFMS-PIS 567 , 2 , 77.1-94.3 mm SL, Paraguay River, Corumbá . ZUFMS-PIS 656 , 1 (plus 8 ex. of R. aurata ), 64.9 mm SL, baía das Antas, Corumbá . ZUFMS-PIS 673 , 1 , 91.0 mm SL, rio Miranda, Corumbá . ZUFMS-PIS 695 , 15 , 60.5-93.3 mm SL, marginal pond at MS 325 Road, Corumbá . ZUFMS-PIS 698 , 2 , 64.2- 89.3 mm SL, marginal pond at MS 325 road, Corumbá . ZUFMS-PIS 700 , 1 , 83.0 mm SL, lago do Jacadigo, Corumbá . ZUFMS-PIS 704 , 1 , 79.1 mm SL, baía Grande, Corumbá . ZUFMS-PIS 826 , 1 , 59.2 mm SL, lago do Cervo, Corumbá. Rio Grande do Sul State : MCP 16304 , 3 + 1 c&s, (3), 69.3-117.3 mm SL, rio Santa Maria, Rosário Sul . MCP 19588 , 2 , (2), 84.5-104.7 mm SL, rio Santa Maria, Rosário Sul . MCP 22841 , 1 , (1), 76.2 mm SL, arroio Ximbocuzinho, São Luiz Gonzaga . MCP 22843 , 4 + 2 c&s, (4), 63.8-97.6 mm SL, rio Uruguay, Uruguaiana . UFRGS 7706 , 1 , 96.6 mm SL, rio Santa Maria, Rosário Sul . UFRGS 8531 , 2 , 66.4-76.4 mm SL, arroio do Salso, Rosário Sul. Paraguay: Departamento de Alto Paraguay : MNHNP 1355 , 5 , 81.0- 82.1 mm SL, río Paraguay, Bahía Negra . MNHNP 1581 , 2 , 58.5 -66.0 mm SL, río Paraguay, Bahía Negra . MNHNP 2343 , 11 , 46.0- 85.2 mm SL, río Paraguay, Puerto Voluntad . MNHNP 3582 , 2 , 61.0-65.0 mm SL, MNHNP 3671 , 1 + 2 c&s, 61.7-97.9 mm SL, río Paraguay, Puerto Esperanza . MNHNP 3672 , 1 c&s, 83.2 mm SL, río Paraguay, Puerto Boquerón . MZUSP 54224 , 1 , 71.6 mm SL, río Paraguay, Puerto Lidia . MZUSP 54227 , 1 , (1), 57.4 mm SL, riacho Celina (lateral branch of the río Paraguay), city not specified. NRM 33313 , 30 (plus 1 ex. of R. aurata ), (4), 49.1-88.4 mm SL, río Paraguay, Bahía Negra . NRM 37673 , 11 (plus 2 ex. of R. aurata ), (4), 56.8-86.3 mm SL, río Paraguay, Bahía Negra. Departamento Central : CZCEN 237 , 3 , 68.3-75.3 mm SL, río Paraguay, Asunción . CZCEN 318 , 11 , 53.1 -88.0 mm SL, río Paraguay, Limpio . CZCEN 319 , 1 , 61.9 mm SL, río Paraguay, Limpio . MNHNP 1911 , 1 , 92.0 mm SL, río Salado, Limpio . MNRJ 24315 , 1 , 80.0 mm SL (estimated, caudal fin regenerated), río Salado, Limpio . MNRJ 24316 , 3 , (2), 65.6-87.5 mm SL, río Salado, Limpio . NRM 41952 , 1 , (1), 86.3 mm SL, dike associated to the lagoYpacaraí, Areguá . NRM 45208 , 15 , (8), 63.3-119.3 mm SL, río Paray, Buey Rodeo . NRM 45303 , 2 , (2), 75.7-75.8 mm SL, río Salado, Limpio. Departamento de Concepción : MNHNP 2748 , 10 , 67.0- 94.2 mm SL, río Paraguay, Concepción . MNHNP 3663 , 6 , 84.0- 98.2 mm SL, arroyo Laguna Penayo, Paso Barreto . NRM 23028 , 11 (plus 1 ex. of R. aurata ), (6), 79.0-112.0 mm SL, arroyo Laguna Penayo, Paso Barreto. Departamento de Cordillera : MNHNP 377 , 1 , 58.5 mm SL, swamp associated to the lago Ypacaraí, San Bernardino. Departamento de Misiones : MNHNP 1841 , 6 , 64.0- 135.2 mm SL, río Tebicuary, Villa Florida . MNHNP 3311 , 2 , 78.0-90.0 mm SL, río Tebicuary , Villa Florida. Departamento de Ñeembucú : CZCEN 320 , 3 , 37.0-45.0 mm SL, arroyo Yacaré, Mburika . MNHNP 1409 , 1 , 40.0 mm SL, Arroyo Paso Cornélio, Humaitá . MNHNP 2574 , 4 , 43.1 -48.0 mm SL, arroyo Paso Cornélio, Humaitá . NRM 32827 , 4 , 45.3-58.1 mm SL, swamp associated to the arroyo Paso Cornélio, Humaitá. Departamento de Paraguarí : ANSP 175151 , 2 , (2), 85.6-105.3 mm SL, río Tebicuary, Caapucú . UMMZ 206043 , 3 , (1), 54.8-109.6 mm SL (discolored),arroyo Mbaey , Paraguarí . Departamento de Presidente Hayes : ANSP 175157 , 2 , 52.4-70.7 mm SL, pool associated to the río Paraguay, Mariano Roque Alonso . MNHNP 1555 , 1, 105.2 mm SL, riacho Siete Puntas (lateral branch of the Río Paraguay), Villa San Jorge . NRM 43371 , 1 , (1), 86.9 mm SL, riacho Siete Puntas (lateral branch of the río Paraguay), Villa San Jorge . NRM 44377 , 9 , (2), 66.7-92.1 mm SL, riacho Siete Puntas (lateral branch of the río Paraguay), Villa San Jorge. Departamento de San Pedro : NRM 44455 , 2 , (2), 75.4-96.4 mm SL, río Paraguay, San Pedro del Ycuamandiyú .

Key to the species of Rineloricaria from the Paraguay River basin

1a. Five lateral plate series in longitudinal rows below the dorsal fin, composed by the dorsal, mid-dorsal, median, mid-ventral, and ventral series ( Fig. 4c ); abdominal plates of anterior complex projected toward lip, surpassing horizontal line around pectoral-fin insertion …………………………………… Rineloricaria cacerensis

1b. Four lateral plate series in longitudinal rows below the dorsal fin, the mid-dorsal plate series absent ( Fig. 4a ); abdominal plates of anterior complex not projected toward lip, ending just about horizontal line around pectoral-fin insertion …………………...................................................… 2

2a. Lateral region of the body just posterior to the pectoral-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 pectoral-fin 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

Figures

Fig. 11. Rineloricaria parva, NRM 37673, 86.3 mm SL, Paraguay River, Bahía Negra, Departamento de Presidente Hayes, Paraguay.

Fig. 12. Hypetrophied odontodes developed in breeding male specimens of Rineloricaria parva, ZUFMS-PIS 567, 94.3 mm SL: a) dorsal view, b) lateral view, c) ventral view.

Fig. 13. Partial map of South America showing the geographical distribution of Rineloricaria parva. Dots = Occurrence, Star = Type locality (Descalvados, Mato Grosso State, Brazil).

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.

Fig. 3. Rineloricaria aurata, NUP 3440, male, 74.1 mm SL, córrego Cancela, affluent of the rio Cuiabá, Paraguay River basin, Nobres, Mato Grosso State, Brazil.

Fig. 8. Rineloricaria lanceolata, CZCEN 316, male, 87.1 mm SL, arroyo Piribebuy, Paraguay River basin, Eusebio Ayala, Departamento de Cordillera, Paraguay.