Oxydoras Orestis Steindachner, 1875: 138 Hemidoras orestes Eigenmann & Eigenmann, 1888: 158 Eigenmann & Eigenmann, 1890: 258 Eigenmann & Eigenmann, 1891: 33 Eigenmann, 1910:394 Hassar orestes Hassar orestis Eigenmann, 1910: 394 Miranda Ribeiro, 1911: 185 Eigenmann, 1925: 356 Gosline, 1945: 23 Fowler, 1951: 492 Burgess, 1989: 217 Eschmeyer, 1998: 1247 Camargo et al ., 2004: 143 Ferraris, 2007: 171 Sabaj Pérez et al ., 2007: 189 Birindelli et al ., 2009: 276 Hassar orestis , NMW Hassar orestis, NMW Hassar ucayalensis , ANSP Hemidoras notospilus Eigenmann, 1912: 196 Eigenmann, 1910: 394 Hassar notospilus Eigenmann, 1925: 356 Gosline, 1945: 23 Burgess, 1989: 217 Eschmeyer, 1998: 1200 Hassar ucayalensis Fowler, 1939: 228 Fowler, 1941b: 390 Gosline, 1945: 23 Fowler, 1945: 61 Fowler,1951:492 Eschmeyer, 1998: 1718 Hassar iheringi Fernández-Yépez, 1968: 13 Mago-Leccia, 1970: 79 Opsodoras notospilus Fernández-Yépez, 1968: 49 Mago-Leccia, 1970: 79 Hassar sp. Moyer et al ., 2004: 555 Hassar ucayalensis Oxydoras orestis Oxydoras orestis Oxydoras orestis Taxonomic revision of thorny catfish genus Hassar (Siluriformes: Doradidae) Birindelli, José L. O. Fayal, Danielle F. Wosiacki, Wolmar B. Neotropical Ichthyology 2011 2011-12-31 9 3 515 542 3JVN3 (Steindachner, 1875) Steindachner 1875 [942,1334,1136,1155] Actinopterygii Doradidae Hassar Animalia Siluriformes 10 525 Chordata species orestis    Figs. 9and 10      Oxydoras Orestis  Steindachner, 1875: 138, pl. 1 [ typelocality: “ Rio Xingu(bei den Wasserfällen) und Rio Iça” (= rio Xingunear rapids and rio Iça)].    Hemidoras orestes.—  Eigenmann & Eigenmann, 1888: 158[change of generic status, Huytahy (=Jutaí), misspelling].—  Eigenmann & Eigenmann, 1890: 258[literature compilation].—  Eigenmann & Eigenmann, 1891: 33[literaturecompilation].—  Eigenmann, 1910:394[literature compilation].—Eigenmann & Fisher, 1917: 422 [ Bolivia, Santarém].   Hassar orestes.— Kindle, 1895[change of generic status, identification key, misspelling].    Hassar orestis. —  Eigenmann, 1910: 394[subsequent designation of typespecies].—  Miranda Ribeiro, 1911: 185[identification key, translation to Portuguese of the original description].—  Eigenmann, 1925: 356[identification key, “Itaituba, Brazil”, “R. Tapajós, Santarém”, “Amazon, Santarém”].—  Gosline, 1945: 23[literature compilation].—  Fowler, 1951: 492[literature compilation];  Burgess, 1989: 217[literature compilation].—  Eschmeyer, 1998: 1247[literature compilation].—Sabaj & Ferraris, 2003: 461 [literature compilation].—  Camargo et al., 2004: 143(in part, distribution, lower Xingu).—  Ferraris, 2007: 171[literature compilation].—  Sabaj Pérez et al., 2007: 189[listed as comparative material].—  Birindelli et al., 2009: 276[gas bladder morphology].   Fig. 9.( a) Lectotype of  Hassar orestis, NMW45428, 66.8 mm SL, ( b) paralectotype of  Hassar orestis,NMW45427, 206.0 mm SL; and ( c) holotype of  Hassar ucayalensis, ANSP68647, 68.9 mm SL. Photos ( b) and ( c) by Mark Sabaj Pérez.     Hemidoras notospilus Eigenmann, 1912: 196, pl. 19, fig. 2 [ typelocality: Crab Falls (= Essequibobasin, Guyana)].—  Eigenmann, 1910: 394[ nomen nudumin species list].    Hassar notospilus.—  Eigenmann, 1925: 356[new combination].—  Gosline, 1945: 23[literature compilation].—  Burgess, 1989: 217[literature compilation].—  Eschmeyer, 1998: 1200[literature compilation].     Hassar ucayalensis Fowler, 1939: 228, figs. 15, 16, 17 [ typelocality: Ucayali Riverbasin, Contamana, Peru].—  Fowler, 1941b: 390[literature compilation].—Eigenmann & Allen, 1942: 135 [diagnosis].—  Gosline, 1945: 23[literature compilation].—  Fowler, 1945: 61[literature compilation].—  Fowler,1951:492[literature compilation].—  Eschmeyer, 1998: 1718[literature compilation].    Hassar iheringi.—  Fernández-Yépez, 1968: 13, fig. 16 [Orinoco, illustration].—  Mago-Leccia, 1970: 79[literature compilation, Orinoco].    Opsodoras notospilus.—  Fernández-Yépez, 1968: 49[new combination, identification key, Orinoco].—  Mago-Leccia, 1970: 79[literature compilation, Orinoco].    Hassarsp.—  Moyer et al., 2004: 555[cladistic analysis based on molecular data].  Type-specimens.  ANSP 68647(1, 68.9 mmSL, holotypeof  Hassar ucayalensis), Contamana, Peru, Jul 1937, W. C. Morrow.  NMW45428 (1, 66.8 mmSL, lectotypeof  Oxydoras orestis[herein designated]);  NMW45428 (2, 47.9-48.0 mm SL, paralectotypesof  Oxydoras orestis); Rio Iça(=rio Iça, tributary of rio Amazonas, AM, Brazil).  NMW45427 (1, 206.0 mm SL);  NMW45429 (2, 148.3-162.0 mm SL);  NMW45430 (1, 198.0 mm SL);  NMW60015 (1 sk, c. 189 mmSL);  NMW78651 (1, 169.0 mm SL); Xingu Cascades(= rio Xingunear rapids, PA, Brazil; all paralectotypesof  Oxydoras orestis).   Non-type specimens. Amazon basin ( Brazil):  ANSP 185357( 1, 105.2 mmSL), rio Trombetas, Santa Cecília, 1°39’59”N 55°57’24”W, Oriximiná, PA,  Oct 1994, R. Reis et al.  BMNH 1926.10.27.262 (1, 73.9 mmSL), rio Amazonas, Monte Alegre, Ternetz.  CAS76797 ( 1, 111.3 mmSL), rio Amazonas, Santarém, PA,  Aug 1924, C. Ternetz.  INPA 17742(1, 48.8 mmSL), near igarapé Curumbaú, rio Brancobasin, 1°2’44’’S 61°51’21’’W, RR,  Nov 1996, L. Chao.  INPA 5312( 1, 166 mmSL), ilha da Marchantaria, Iranduba, AM,  Feb 1976.  MPEG 1452( 1, 196.2 mmSL), rio Xingu, Ilha de Mucuripe, PA,  Jun 1984,  Paulo Sá.  MPEG 2219( 1, 216.4 mmSL), rio Xingu, Baía Sousel, PA,  Dec 1984,  Paulo Sá.  MZUSP 3719( 1, 143.6 mmSL), rio Tapajós, c. 2°25’S 54°44’W, Santarém, PA.  MZUSP 6721(1, 79.4 mmSL), rio Negro, c. 3°0’S 60°0’W, Manaus, AM.  MZUSP 6991(1 c&s, 65.7 mmSL), rio Madeira, c. 3°53’S 59°5’W, Nova Olinda do Norte, AM,  Nov 1967.  MZUSP 7650(3, 65.1-72.7 mmSL), rio Amazonas, Boca do Lago São José Açu, c. 2°40’S 56°37’W, Parintins, AM,  Jul 1967.  MZUSP 9516(7, 137.7- 170.7 mmSL), rio Tapajós, Aveiro, c. 3°35’S 55°20’W, PA.  MZUSP 9531(2, 103.8- 141.4 mmSL), rio Tapajós, Alter do Chão, PA.  MZUSP 9536(2, 141.0- 162.4 mmSL), rio Nhamundá, PA,  Aug 1968.  MZUSP 9547(2, 137.3- 156.1 mmSL), rio Uatumã, São Sebastião do Uatumã, AM,  Sep 1968.  MZUSP 15528( 1, 195.8 mmSL), rio Trombetas, Reserva Biológica do Trombetas, c. 1°25’0”S 56°37’0”W, PA.  MZUSP 15762(4, 133.0-156.0 mm SL), rio Trombetas, Reserva Biológica do Trombetas, Igapó do Lago Farias, c. 1°25’S 56°37’W, PA,  Jul 1979,  Castro.  MZUSP 21915( 1, 146.4 mmSL), rio Tapajós, Itaituba, c. 4°17’S 55°59’W, PA.  MZUSP 31696( 1, 127.2 mmSL), rio Tefé, Jurupari, c. 3°22’S 64°43’W, Tefé, AM,  Aug 1979, M. Goulding.  MZUSP 32539(142, 109.2- 180.6 mmSL), rio Tapajós, São Luis, c. 4°27’S 56°15’W, PA, M. Goulding.  MZUSP 32540(12, 125.9- 164.3 mmSL), rio Tapajós, c. 4°17’S 55°59’W, Itaituba, PA.  MZUSP 32541(2, 117.3- 209.2 mmSL), rio Trombetas, c. 1°46’S 55°52’W, Oriximiná, PA.  MZUSP 32542(2 sk, 237, 140.6- 246.8 mmSL), rio Xingu, Belo Monte, c. 3°7’S 51°42’W, PA, M. Goulding.  MZUSP 46010(1 c&s, 11, 57.8-80.7 mmSL), rio Solimões, Coari, Ilha de Sorubim, AM.  MZUSP 49179(4, 122.0- 139.2 mmSL), rio Trombetas, c. 1°46’S 55°52’W, Oriximiná, PA.  MZUSP 49181(13, 122.3- 187.1 mmSL), rio Tapajós, Monte Cristo, c. 4°5’S 55°37’W, PA.  MZUSP 49183(13, 147.4- 200.5 mmSL), rio Tapajós, Barreirinha, PA,  Nov 1970.  MZUSP 49184(2, 143.6-156.0 mm SL), rio Tapajós, São Luis, c. 4°27’S 56°15’W, PA.  MZUSP 50839(1 c&s, 2, 74.6-88.8 mmSL), rio Solimões, near Ilha Baruruá, mouth of rio Jutaí, c. 2°44’S 66°46’W, AM,  Dec 1968.  MZUSP 56680(3, 68.5-83.6 mmSL), rio Amazonas, rio Jutaí, 2°53’17”S 67°0’24”W, AM.  MZUSP 56865(1, 56.0 mm SL), rio Madeira, 3°38’35”S 59°2’50”W,AM.  MZUSP 74680( 1, 126.2 mmSL), rio Tefé, Jurupari, c. 3°22’S 64°43’W, Tefé, AM.  MZUSP 82256( 1, 186.6 mmSL), rio Xingu, Belo Monte, c. 3°7’S 51°42’W, PA.  MZUSP 86781(1, 164.0 mm SL), rio Xingu, Belo Monte, c. 3°7’S 51°42’W, PA.  Amazonbasin ( Peru) :  ANSP 181090(1, 67.2 mmSL), near Iquitos, mouth of río Itaya, 3º40’36”S 73º14’37”W,  Aug 2005, M. H. Sabaj et al.  ANSP 181094(10, 87.0- 106.4 mmSL), near Iquitos, Peru,  Aug 2006, M. H. Sabaj et al.  INHS 53720(2, 59.0- 83.8 mmSL), rio Nanaydrainage, Pampa Chica, 4.5 Kmfrom Iquitosdowntown, near Loreto, 3°45’9”S 73°17’0’’W,  Aug 1999. Essequibo basin ( Guyana):  ANSP 175875( 1, 140.8 mmSL), Essequibo river, Maipuri, 4°45’43”N 58°45’52”W,  Jan 1997, W. Saul.  ANSP 175876(1, 82.1 mmSL), Essequibo river, 4°34’17”N 58°35’17”W, Maipuri,  Jan 1997, W. Saul et al.  ANSP 179642( 1, 119.9 mmSL), Rupununi river, 3°53’41”N 59°17’37”W,  Oct 2002, M. H. Sabaj et al.  BMNH 1971.4.14.52 (1, 82.7 mmSL), Rupununi river, at sandcreek road crossing South Savannas( RHL602),  Apr 1961, R. Lowe-McConnel.  Orinocobasin ( Colombia) :  AUM28765 (4, 45.3-58.9 mmSL), río Manacias, río Metabasin, Puerto Gaitan, Colombia,  X-1978,  J. S. Ramsey et al.  Orinocobasin ( Venezuela) :  ANSP 152870(1, 43.9 mmSL), Isla Isabela, between Palua and Ciudad Bolívar, 8°18’43”N 65°56’52”W,  Nov 1979, J. G. Lundberg.  ANSP 160904(1, 69.6 mmSL), mouth of río Cuchivero, c. 7°40’N 65°57’W, Bolívar,  Nov 1985, B. Chernoff.  ANSP 165493( 1, 146.7 mmSL), río Capanaparo, mouth of Caño Las Varitas, near San Fernandode Apure, c. 7°2’N 67°25’W,  Nov 1989, S. Schaefer.  ANSP 165787(1, 45.0 mm SL), río Caura, 7°38’42”N 64°52’48”W, Bolívar,  Nov 1985, B. Chernoff.  ANSP 166595( 1, 121.2 mmSL), Anzoategui, Soledad, l. Tineo, 8°11’25”N 63°28’20”W,  Jan 1987, M. Rodriguez & S. Richardson.  ANSP 166597(1, 70.9 mmSL), Caicara, l. Bartolico, 7°38’30”N 66°7’W,  Jan 1987, M. Rodriguez & S. Richardson.  ANSP 180294(1 sk, 4, 162.9- 225.2 mmSL), río Ventuari, Macuruco, San FernandodeAtabapo, 4°45’0’’N 66°21’13”W,  Apr 2004, M. H. Sabaj et al.  ANSP 180295(1 sk, not measured), río Orinoco, río Ventuari, Macuruco, 4º18’51”S 66º17’32”W, San Fernando de Atabapo,  Apr 2004, M. H. Sabaj et al.  ANSP 182221(2, 119.4- 159.1 mmSL), río Ventuari, 4°6’55”N 66°45’52”W,  May 2004,  Sabaj et al .  ANSP 182796( 1, 101.3 mmSL), río Manapiare, San Juan de Manapiare, 5°26’12”N 66°6’45”W,  Apr 2004, M. H. Sabaj et al.  CAS58084 (1, 54.1 mmSL), río Orinoco, Delta Amacuro,  Nov 1979, J. N. Baskin & J. G. Lundberg.  INHS 35082(3, 90.5-95.4 mmSL), Laguna Castillero, 7°38’20”N 66°9’W, Bolívar,  Jan 1988, M. A. Rodriguez.  MZUSP 105827(1 sk, 144.7 mmSL), río Ventuari, 4°13’37’’N 66°25’26’’W, Puerto Maldonado,  Apr 2010, J. L. Birindelli et al.  UMMZ 214799(3, 142.9- 172.1 mmSL), río San Jose, 10 kmfrom mouth of San Joseand río Guariquito,  Feb 1987, W.L. Fink. No data:  MZUSP 84553(2 c&s, not measured).   Diagnosis.  Hassar orestisis diagnosed among its congeners by having the 1 stthrough 8 th(modally 3 rd) midlateral scute as the anteriormost with median thorn ( vs.9 ththrough 17 th), and tip of upper caudal-fin lobe usually darkened ( vs.rarely or never darkened).  Hassar orestisis further distinguished from  H. affinisand  H. gabiruby having gas bladder with many well-branched diverticula on margins of entire bladder ( vs.gas bladder with two rounded or weakly-branched diverticula restricted to each side of anterior chamber of the bladder [rarely one extra pair on the posterior chambers]); and gas bladder triangular posteriorly, each posterior chamber extended into a short terminal diverticulum sharing medial septum with its pair ( vs.gas bladder posteriorly rounded, lacking terminal diverticula).  Hassar orestisis yet distinguished from  H. affinisby having the distal tip of the first branched dorsal-fin rays and membranes pale ( vs.first branched dorsal-fin rays and membranes distally darkened); and 10 thmidlateral scute 6.2-18.0%, mean 12.9%, of relative body depth ( vs.3.1-5.1%, mean 4.1%, of relative body depth).  Hassar orestisis also distinguished from  H. gabiruby having body depth at dorsal-fin origin 16.8-22.2%, mean 21.1%, SL ( vs.24.3-33.1%, mean 25.8%, SL), body depth at anal-fin origin 10.0- 14.7%, mean 13.1%, SL ( vs.15.9-20.7%, mean 17.3%, SL), and caudal peduncle depth 4.3-6.4%, mean 5.5%, SL ( vs.6.6-8.6%, mean 7.1%, SL).   Description.Morphometric data are summarized in Tables 3and 4; morphometric data for typespecimens in Table 4; typespecimens illustrated in Fig. 9, additional specimens in Fig. 10. Largestspecimenexamined 246.8 mmSL (MZUSP 32542).Dorsal profile of head rising moderately, evenly (usually in smaller specimens) or strongly convex (especially in larger specimens) from snout tip to anterior margin of orbit, and relatively straight form latter point to dorsal-fin spine. Dorsal profile of body descending gradually, approximately straight from dorsal-fin spine to caudal peduncle. Ventral contour shallowly concave from snout tip to pectoral girdle, and slightly convex from latter point to caudal peduncle. Caudal peduncle short with shallow hourglass shape in lateral view. Body elongate with prominent conical snout. Mouth subterminal, each premaxilla bearing small patch of approximately 5 to 10 acicular teeth, and each dentary with approximately 10 to 20 acicular teeth. Oval orbit with adipose eyelid weakly developed in juveniles (SL< 14 cm), extended slightly beyond anterior and posterior limits of eye, and welldeveloped in adults (SL> 14 cm), extended well beyond anterior margin of the eye. Eyes positioned about half way between tip of snout and dorsal-fin origin. Three pairs of barbels (maxillary, inner and outer mental), all fimbriate.Maxillary barbel usually reaching base of first pectoralfin ray; with 8 to 16 (mode 12, n=101) fimbriae along ventrolateral face. Inner and outer mentonian barbels of approximately equal size, covered with many rounded papillae, and falling short of ventralmost opening of gill slit. Gill rakers on first gill arch 10 to 15; gill rakers completely absent or remnant on remaining arches. Accessory branchial lamellae on inner face of first gill arch well developed in approximately ten rows from insertion of rakers to origin of branchial filaments (but not contacting the latter); accessory lamellae gradually reduced on remaining (second to fifth) gill arches. Lateral-line tubules ossified, forming row of 31 to 34 (mode 32, n=101) midlateral scutes beginning with infranuchal. Three tympanal scutes, inconspicuous, usually without emergent thorn. Infranuchal scute with dorsal wing extremely thin and ventral wing dilated, expanded anteriorly, connected to posterior cleithral process; scute usually without medial thorn. Postinfranuchal scutes reduced anteriorly, non-overlapping; each with posterior margin bicuspid (without medial thorn) or tricuspid (including medial thorn), latter condition usually starting at 3 rdscute (range 1 stthrough 8 th, n=101); medial thorn and dorsal and ventral wings gradually increasing in size posteriorly; scutes with weakly serrated posterior margin and overlapping. Dorsal-fin II,6 (n=101), triangular with distal margin approximately straight, vertical when erected. Dorsal-fin spine slightly compressed and curved, with relatively small antrorse serrations along anterior margin (serrations reduced or absent on distal third); slightly larger retrorse serrations along posterior margin (serrations absent on proximal portion). Pectoral fin modally I,8, range I,7-9 (n=99); distal margin straight, oblique relative to body axis. Pectoral-fin spine slightly depressed and curved, with antrorse serrations along anterior margin (serrations absent on distalmost portion); slightly larger retrorse serrations along posterior margin (serrations larger distally). Pelvic fin i,6 (n=97); distal margin rounded. Anal fin modally iii,8, range iii-v,7-9 (n=25); subtriangular with scarcely rounded distal margin. Adipose fin relatively small, teardrop-shaped, with rounded free posterior margin. Caudal fin i,7/8,i (n=101, rarely i,8/8,i or i,7/7,i), distinctly forked, with lobes approximately equal in size. Gas bladder ( Fig. 4) moderately large, cordiform. Bundles of diverticula present along the anterior, lateral, and posterior margins of entire bladder in small specimens (< 50 mmSL); diverticula become thinner and more branched in larger specimens (lateral diverticula slightly more developed than in  H. wilderi). Gas bladder triangular posteriorly, each posterior chamber extended into a short terminal diverticulum sharing medial septum with its pair and possessing smaller lateral diverticula.  Osteology.Osteological features of head and anterior body in Fig. 11; hyoid and branchial skeleton in Fig. 12; pectoral girdle in Fig. 13; pelvic girdle in Fig. 14. Cranial roof bones and nuchal plates well developed and ornamented with delicate small grooves and striae; relatively straight between orbits and triangulary arched (almost reaching 90°) near dorsal-fin origin.   Fig. 13.Pectoral girdle in dorsal (left) and ventral (right) views of  Hassar orestis, MZUSP105827, 144.7 mm SL. Scale bar = 5 mm. Mesethmoid extremely elongate, arrow-shaped with paired median lateral processes and sharp anterior tip (bifid only in juveniles), lacking cornua for articulation with premaxillae; dorsal profile concave in lateral view, especially near median lateral processes. Lateral ethmoid long, rectangular, participating in externally visible portion of cephalic shield and contacting infraorbital 1 anterolaterally. Nasal long, tubular, reaching to median lateral process of mesethmoid anteriorly. Cranial fontanel divided by epiphyseal bar into a large, elongate anterior opening beginning at mesethmoid, and a smaller posterior opening extended posteriorly as a narrow Vshaped notch in anterior margin of parieto-supraoccipital; lateral margins of cranial fontanel bordered by frontals. Dorsal half of orbit rounded, distinctly concave in dorsal view, completed by lateral ethmoid, frontal and sphenotic. Four infraorbitals; first one long and slender, with anterior wing extended well beyond concavity for anterior naris, articulating with the lateral border of the mesethmoid immediately anterior to median lateral process; remaining infraorbitals long, tubular, completing orbit. Sphenotic with well-developed lateral process (articulated with infraorbital 4). In a few specimens (ANSP 165493, 166595) there is a small gap in the sutural joint of the sphenotic, parietosupraoccipital and frontal bones. Epioccipital forming lateral border of cranium, and with well-developed laminar posterior process, composed of a vertical portion (distally dilated and sutured to posterior nuchal plate) and a horizontal portion. Anterior nuchal plate reduced to a small diamond-shaped bone surrounded by parieto-supraoccipital and middle nuchal plate. Nuchal foramina wide, somewhat triangular, enclosed by parieto-supraoccipital, epioccipital and middle nuchal plate. In most specimens, there is a small foramen between pterotic, posttemporo-supracleithrum and epoccipital. Vomer with reduced anterolateral processes, and with anterior portion enclosed by expanded mesethmoid. Parasphenoid long, anterior tip bifid, posterior portion small. Cranium with well-developed ventral keel between orbits, greatly formed by enlarged orbitosphenoid. Optic foramen bounded by pterosphenoid and parasphenoid. Trigeminofacial foramen enclosed by pterosphenoid and prootic. Basioccipital with laminar ventral extension sutured to ventral extension of transcapular process and forming a thin ring-like arch surrounding the aorta. Premaxilla small, somewhat triangular with apex articulating with mesethmoid, and ventral face with small concave patch with few acicular teeth. Maxilla relatively long, curved inward. Autopalatine extremely elongate, rod-like, with weakly dilated ends. Dentary with small patch of acicular teeth. Coronomeckelian bone extended, sutured to both dentary and anguloarticular. Mandibular sensory branch with three pores on lower jaw.   Fig. 14.Pelvic girdle in dorsal view of  Hassar orestis, MZUSP105827, 144.7 mm SL. Scale bar = 5 mm. Suspensorium elongate; hyomandibula elongate with laminar medial extension restricted to anterior portion; metapterygoid small, somewhat triangular, medially surrounded by expanded entopterygoid, which is medially connected to lateral ethmoid. Opercle subtriangular, contacting relatively large interpreopercle. Urohyal small, with well-developed ventral process. Ventral hypohyal large, elongate, with somewhat spiny anterior tip, joined to anterior ceratohyal via suture on anterior face, cartilage posteriorly. Dorsal hypohyal much smaller, with acute posterior margin. Small fenestra enclosed by ventral and dorsal hypohyal. Anterior ceratohyal rod-like with dilated tips, anteriorly expanded by a small process sutured to ventral hypohyal, posteriorly joined to posterior ceratohyal via cartilage and suture. Seven branchiostegal rays, five attached to anterior ceratohyal and two to interceratohyal cartilage. Five branchial arches, elongate. Three basibranchials (first one absent); basibranchials two and three elongate, ossified with cartilaginous caps; fourth one longest, cartilaginous. Three hypobranchials; first and second ones elongate, ossified with cartilaginous caps (in specimens> 80 mmSL), or broad with continuous cartilaginous margin (in specimens < 60 mmSL); third one short and broad, cartilaginous, medially attached between basibranchials three and four. Five ceratobranchials; first four narrow, elongate, ossified with cartilaginous caps; dorsal half of cartilaginous cap of fourth ceratobranchial expanded anteriorly as narrow process parallel to fourth basibranchial; fifth ceratobranchial with narrow proximal stalk and oval tooth patch (bearing many acicular teeth) with laminar lateral border. Five epibranchials; first four elongate, ossified with cartilaginous caps; third one with small posterior process; fifth one small, rod-like, cartilaginous. Two pharyngobranchials, first two absent; third elongate, ossified with cartilaginous caps; fourth small, ossified portion semicircular with rounded margin capped in cartilage, connected to second pharyngobranchial and third and fourth epibranchials and supporting lenticular plate with many acicular teeth. Accessory pharyngobranchial cartilage small, rectangular, connected to first two epibranchials and second pharyngobranchial. Total vertebrae 35 (n=1) or 36 (n=3). Centra 1-5 fused into the Weberian complex, sixth and seventh centra completely sutured to complex centra, eighth centrum partially sutured into seventh (remnant of intervertebral disk between seventh and eighth centrum present). Aortic passage completely enclosed by superficial ossifications. Müllerian ramus with ossified proximal portion oval-shaped in outline, narrower distal end gradually transitioning into spherical cartilaginous knob directed posteroventrally into anterior chamber of gas bladder. Fifth centrum either lacks or possesses process-like parapophyses. Vertebrae 6-14 (n=3) or 6-15 (n=1) bearing distinct pairs of simple ribs. Eight (n=4) dorsal-fin pterygiophores, 11 (n=4) pelvic-fin pterygiophores; 13 (n=4) dorsal and 12 (n=1) or 13 (n=3) ventral caudal-fin procurrent rays. Caudal fin with hypural fusion pattern PH; HY 1+2; HY 3+4; HY 5 (1 abnormal specimen [MZUSP 105837] with HY3 and HY4 distinct); hypurapophyses TypeC ( sensuLundberg and Baskin, 1969:15). Pectoral girdle subtriangular in ventral view, elongated anteriorly with broad, truncate anterior margin, lateral margins slightly concave. Coracoid posterior process moderate in size. Ventral surface of pectoral girdle completely covered by muscle and skin (not visible externally). Abductors superficialisand arrector ventralismuscles separated by oblique (approximately at 45° in relation to body axis) bony crest on ventral face of coracoid. Posterior cleithral process subtrapezoidal, in lateral view, deep with obtuse posterior margin. Basipterygium with internal anterior process partially incorporated into main body of basipterygium; external anterior process distinct, rod-like, moderately long; ossified posterior process well developed, with acute posterior tip attenuated by cartilage.  Coloration.In alcohol, head and body tan to brown, or grey, countershaded. Faint dark stripe from anterior margin of upper lip to anterior margin of eye. A conspicuous dark blotch on the first three branched dorsal-fin rays and membranes, blotch starting from midlength of rays and membranes and almost reaching their distal tips, which are pale. Tip of upper caudalfin lobe usually darkened.   Fig. 15.  Hassar orestis, MZUSP103327, 106.5 mm SL, rio Jari, Monte Dourado, PA, photographed live. In life, ground color yellowish or greenish laterally and white ventrally; lower lip pinkish ( Fig. 15). Eye silvery, distinctly contrasted with pale surrounding adipose tissue.   Distribution.  Hassar orestisis distributed in the Amazon, Orinoco and Essequiboriver basins, in Bolivia, Brazil, Colombia, Guyana, Peru, and Venezuela, particularly in the Amazon lowlands ( Fig. 6).  Hassar orestisis apparently absent in the upper Tapajós, middle and upper Xingu, and Tocantins basins.   Ecology.Specimens of  Hassar orestisare usually collected in swift water over sandy beaches (substrate sometimes with fine gravel or mud), and often in the main channel of large rivers. Mature males of  H. orestisdevelop an elongate and flexible extension to dorsal-fin spine.   Etymology.Named in honor of Orestes Saint John, member of the Thayer expedition who collect the typesspecimens of  Hassar orestis. The species name was given by Louis Agassiz, the leader of the Thayer Expedition, as indicated by Steindachner in the original description: “  Oxydoras OrestisAgass.in lit.” “...von Herrn Orestes Santi-John gesammelt, und letzterem zu Ehren bezeichnete Prof.Agassiz diese schöne Art  Oxydoras Orestis...” (=Orestes Saint John, in honor to whom Prof. Agassiz described  Oxydoras orestis).   Remarks.  Hassar orestiswas described based on specimens collected in two localities: rio Xingu near rapids (“bei den Wasserfällen”, or as it appers on the label “Xingu, Cascades”) and rio Iça. The Thayer Expedition collected fishes at two localities in the rio Xingu, at Porto de Moz, near the mouth of the rio Xingu, and “Cascades”. The latter locality probably refers to some place in the rio Xingu near Belo Monte, just downstream of the Volta Grande rapids, where the rio Xingu begins (upstream) to have rocky bottom and rapids. Examined specimens from Belo Monte are identical to the typesof  Hassar orestisin overall morphology, and herein referred to as  Hassar orestis. The Volta Grande rapids seem to be the upstream geographical limit of  Hassar orestisin the Xingu basin.  Steindachner (1875)described  Oxydoras orestis, currently  Hassar orestis,noting morphometric differences between juveniles and adults. According to him, juveniles have shorter snout and vestigial adipose eyelid. Both characters are corroborated in this study.  Eigenmann (1912, 1925) proposed  Hemidoras notospilus, from the EssequiboRiver in Guyana, as a valid species. The holotypeof  H. notospilus(FMNH 53184) is currently missing (Sabaj & Ferraris, 2003:461; Sabaj Pérez, pers. comm. 2011), but the specimen is clearly assignable to  Hassarbased on Eigenmann’s (1912)illustration (Plate 19, fig. 2), and is also a juvenile, with a length (probably TL) reported as 7 cm( Eigenmann, 1912: 196). The only difference between specimens from the EssequiboRiver is that most individuals have tympanal and infranuchal scutes with emergent median thorns, whereas most examined specimens from the Amazonas-Solimões and Negro basins lack this feature. In the absence of other conspicuous differences between specimens from the EssequiboRiver and other localities, we agree with previous authors ( e.g., Sabaj & Ferraris, 2003) in considering  Hemidoras notospilusa junior synonym of  Hassar orestis.  Fowler (1940)described  Hassar ucayalensisfrom the río Ucayali, upper Amazon basin in Peru. Comparisons of juveniles and adults of  H. orestiswith the holotypeof  H. ucayalensis(SL= 6.89 cm; ANSP 68647) revealed only a difference in the number of secondary maxillary barbels ( 8-16 in  H. orestisvs. 3 inthe holotypeof  H. ucayalensis). We believe that the reduced number of maxillary-barbel fimbriae might be best attributed to damaging and poor preservation of the holotypeof  H. ucayalensis. In the absence of additional differences that we could identify, the suspicion of Sabaj & Ferraris (2003) that  H. ucayalensisis a junior synonym of  H. orestisis corroborated. To avoid further taxonomic changes, we herein designated as lectotypeof  Hassar orestisa specimen from rio Içain the upper Brazilian Amazon, near the Peruvian Amazon. [1003,1256,1232,1251] den Wasserfallen rio Xingu Rio Xingu 10 525 1 Ica ANSP Peru Contamana 11 526 ANSP 68647 1 holotype NMW 45428 NMW Peru 13 528 11 526 1 lectotype NMW 45428 NMW Amazonas, AM Brazil Rio 13 528 1 Ica paralectotype NMW 45427 [266,591,252,269] NMW Brazil 13 528 1 Ica paralectotype NMW 45429 NMW Brazil 13 528 1 Ica paralectotype NMW 45430 [338,637,281,298] NMW Brazil 13 528 1 Ica paralectotype NMW 60015 NMW Brazil 13 528 1 Ica paralectotype NMW 78651 NMW Xingu Cascades Brazil rio Xingu 13 528 1 paralectotype 1994-10 ANSP Oriximina, PA Brazil 1.6663889 Santa Cecilia 21 -55.95667 rio Trombetas 13 528 ANSP 185357 1 BMNH Monte Alegre & Ternetz Brazil rio Amazonas 13 528 BMNH 1926.10 1 CAS 76797 1924-08 CAS Santarem, PA Brazil rio Amazonas 13 528 1 1996-11 INPA Brazil -1.0455555 rio Branco 21 -61.85583 Curumbau 13 528 INPA 17742 1 1976-02 INPA Iranduba, AM Brazil ilha da Marchantaria 13 528 INPA 5312 1 1984-06 MPEG Ilha de Mucuripe, PA Brazil rio Xingu 13 528 MPEG 1452 1 [191,281,677,694] Brazil Paulo Sa 13 528 1 1984-12 MPEG Sousel, PA Brazil rio Xingu 13 528 MPEG 2219 1 Bahia [341,427,705,722] Brazil Paulo Sa 13 528 1 MZUSP Santarem, PA Brazil -2.4166667 rio Tapajos 1307 -54.733334 13 528 MZUSP 3719 1 MZUSP Manaus, AM Brazil -3.0 rio Negro 1307 -60.0 13 528 MZUSP 6721 1 1967-11 MZUSP Nova Olinda do Norte, AM Brazil -3.8833332 rio Madeira 1307 -59.083332 13 528 MZUSP 6991 1 1967-07 MZUSP Parintins, AM Brazil -2.6666667 Boca do Lago Sao Jose Acu 1307 -56.616665 rio Amazonas 13 528 MZUSP 7650 1 MZUSP Brazil -3.5833333 Aveiro 1307 -55.333332 rio Tapajos 13 528 MZUSP 9516 1 MZUSP Alter do Chao, PA Brazil rio Tapajos 13 528 MZUSP 9531 1 1968-08 MZUSP Brazil rio Nhamunda 13 528 MZUSP 9536 1 1968-09 MZUSP Sao Sebastiao do Uatuma, AM Brazil rio Uatuma 13 528 MZUSP 9547 1 MZUSP Brazil -1.4166666 Reserva Biologica do Trombetas 21 -56.616665 13 528 MZUSP 15528 1 1979-07 MZUSP Brazil -1.4166666 Igapo do Lago Farias 1308 -56.616665 13 528 MZUSP 15762 1 [129,194,1137,1154] Brazil Castro 13 528 1 MZUSP Brazil -4.2833333 Itaituba 1306 -55.983334 rio Tapajos 13 528 MZUSP 21915 1 1979-08 MZUSP Tefe, AM Brazil -3.3666668 Jurupari 1307 -64.71667 rio Tefe 13 528 MZUSP 31696 1 MZUSP M. Goulding Brazil -4.45 Sao Luis 1306 -56.25 rio Tapajos 13 528 MZUSP 32539 1 MZUSP Itaituba, PA Brazil -4.2833333 rio Tapajos 1306 -55.983334 13 528 MZUSP 32540 1 MZUSP Oriximina, PA Brazil -1.7666667 rio Trombetas 1308 -55.866665 13 528 MZUSP 32541 1 MZUSP M. Goulding Brazil -3.1166666 Belo Monte 1307 -51.7 rio Xingu 13 528 MZUSP 32542 1 MZUSP Coari & Ilha de Sorubim, AM Brazil rio Solimoes 13 528 MZUSP 46010 1 MZUSP Oriximina, PA Brazil -1.7666667 rio Trombetas 1308 -55.866665 13 528 MZUSP 49179 1 MZUSP Brazil -4.0833335 Monte Cristo 1307 -55.616665 rio Tapajos 13 528 MZUSP 49181 1 1970-11 MZUSP Barreirinha, PA Brazil rio Tapajos 13 528 MZUSP 49183 1 MZUSP Brazil -4.45 Sao Luis 1306 -56.25 rio Tapajos 13 528 MZUSP 49184 1 1968-12 MZUSP Brazil rio Solimoes -2.7333333 rio Jutai 1307 -66.76667 Ilha Barurua 13 528 MZUSP 50839 1 MZUSP Brazil -2.8880553 rio Jutai 21 -67.00667 rio Amazonas 13 528 MZUSP 56680 1 MZUSP Brazil -3.6430554 rio Madeira 21 -59.047222 13 528 MZUSP 56865 1 MZUSP Tefe, AM Brazil -3.3666668 Jurupari 1307 -64.71667 rio Tefe 13 528 MZUSP 74680 1 MZUSP Brazil -3.1166666 Belo Monte 1307 -51.7 rio Xingu 13 528 MZUSP 82256 1 MZUSP Amazon Peru -3.1166666 Belo Monte 1307 -51.7 rio Xingu 13 528 MZUSP 86781 1 2005-08 ANSP Peru -3.6766667 rio Itaya 21 -73.24361 Iquitos 13 528 ANSP 181090 1 [129,768,1886,1903] 2006-08 ANSP Iquitos & Peru Peru 13 528 ANSP 181094 1 1999-08 INHS Peru rio Nanay -3.7525 Km 21 -73.28333 Pampa Chica 13 528 INHS 53720 1 Loreto 1997-01 ANSP Guyana 4.7619443 Maipuri 21 -58.764446 Essequibo river 13 528 ANSP 175875 1 1997-01 ANSP Maipuri Guyana 4.5713887 Essequibo river 21 -58.588055 13 528 ANSP 175876 1 2002-10 ANSP Guyana 3.894722 Rupununi river 21 -59.29361 13 528 ANSP 179642 1 1961-04 BMNH, RHL Guyana South Savannas Rupununi river 13 528 BMNH 1971.4, RHL602 1 Colombia Orinoco 13 528 1 AUM 28765 1978-10 AUM Puerto Gaitan & Colombia Colombia rio Manacias 13 528 1 Meta J. S. Ramsey & Orinoco Venezuela Venezuela 13 528 1 1979-11 ANSP Venezuela 8.311945 Isla Isabela 21 -65.94778 13 528 ANSP 152870 1 Bolivar 1985-11 ANSP Venezuela 7.6666665 rio Cuchivero 1303 -65.95 13 528 ANSP 160904 1 Bolivar 1989-11 ANSP Venezuela rio Capanaparo 7.0333333 San Fernando 1303 -67.416664 Cano Las Varitas 13 528 ANSP 165493 1 Apure 1985-11 ANSP Venezuela 7.645 rio Caura 21 -64.880005 13 528 ANSP 165787 1 Bolivar 1987-01 ANSP Venezuela 8.190278 Tineo 21 -63.47222 Soledad 13 528 ANSP 166595 1 Anzoategui 1987-01 ANSP Venezuela 7.6416664 Bartolico 917 -66.11667 Caicara 13 528 ANSP 166597 1 2004-04 ANSP Venezuela rio Ventuari 4.75 San Fernando 21 -66.35361 Macuruco 13 528 ANSP 180294 1 2004-04 ANSP Venezuela rio Orinoco -4.314167 Macuruco 21 -66.29222 rio Ventuari 13 528 ANSP 180295 1 2004-05 ANSP Venezuela 4.115278 rio Ventuari 21 -66.76444 13 528 ANSP 182221 1 [1056,1162,971,988] Venezuela Sabaj 13 528 1 2004-04 ANSP Venezuela 5.436667 San Juan de Manapiare 21 -66.112495 rio Manapiare 13 528 ANSP 182796 1 CAS 58084 1979-11 CAS Venezuela rio Orinoco 13 528 1 Delta Amacuro 1988-01 INHS Venezuela 7.638889 Laguna Castillero 917 -66.15 13 528 INHS 35082 1 Bolivar 2010-04 MZUSP Puerto Maldonado Venezuela 4.2269444 rio Ventuari 21 -66.42389 13 528 MZUSP 105827 1 1987-02 UMMZ San Jose Venezuela rio Guariquito rio San Jose 13 528 UMMZ 214799 1 [1100,1448,1230,1247] MZUSP Venezuela 13 528 MZUSP 84553 1