Hassar orestis ( Steindachner, 1875 )

Birindelli, José L. O., Fayal, Danielle F. & Wosiacki, Wolmar B., 2011, Taxonomic revision of thorny catfish genus Hassar (Siluriformes: Doradidae), Neotropical Ichthyology 9 (3), pp. 515-542 : 525-533

Hassar orestis ( Steindachner, 1875)

Figs. 9 and 10

Oxydoras Orestis Steindachner, 1875: 138 , pl. 1 [type locality: “ Rio Xingu (bei den Wasserfällen) und Rio Iça ” (= rio Xingu near 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 type species].— 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].

Hemidoras notospilus Eigenmann, 1912: 196 , pl. 19, fig. 2 [type locality: Crab Falls (= Essequibo basin, Guyana)].— Eigenmann, 1910: 394 [nomen nudum in 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 [type locality: Ucayali River basin, 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].

Hassar sp. — Moyer et al., 2004: 555 [cladistic analysis based on molecular data].

Type-specimens. ANSP 68647 (1, 68.9 mm SL, holotype of Hassar ucayalensis ), Contamana , Peru , Jul 1937, W. C. Morrow. NMW 45428 (1, 66.8 mm SL, lectotype of Oxydoras orestis [herein designated]) ; NMW 45428 (2, 47.9-48.0 mm SL, paralectotypes of Oxydoras orestis ); Rio Iça (=rio Iça, tributary of rio Amazonas, AM, Brazil) . NMW 45427 (1, 206.0 mm SL) ; NMW 45429 (2, 148.3-162.0 mm SL) ; NMW 45430 (1, 198.0 mm SL) ; NMW 60015 (1 sk, c. 189 mm SL) ; NMW 78651 (1, 169.0 mm SL); Xingu Cascades (= rio Xingu near rapids, PA, Brazil; all paralectotypes of Oxydoras orestis ) .

Non-type specimens. Amazon basin ( Brazil): ANSP 185357 (1, 105.2 mm SL), 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 mm SL), rio Amazonas , Monte Alegre, Ternetz . CAS 76797 (1, 111.3 mm SL), rio Amazonas , Santarém, PA, Aug 1924 , C. Ternetz. INPA 17742 (1, 48.8 mm SL), near igarapé Curumbaú, rio Branco basin, 1°2’44’’S 61°51’21’’W, RR, Nov 1996 , L. Chao. INPA 5312 (1, 166 mm SL), ilha da Marchantaria , Iranduba, AM, Feb 1976 . MPEG 1452 (1, 196.2 mm SL), rio Xingu , Ilha de Mucuripe, PA, Jun 1984 , Paulo Sá . MPEG 2219 (1, 216.4 mm SL), rio Xingu , Baía Sousel, PA, Dec 1984 , Paulo Sá . MZUSP 3719 (1, 143.6 mm SL), rio Tapajós , c. 2°25’S 54°44’W, Santarém, PA . MZUSP 6721 (1, 79.4 mm SL), rio Negro , c. 3°0’S 60°0’W, Manaus, AM . MZUSP 6991 (1 c&s, 65.7 mm SL), rio Madeira , c. 3°53’S 59°5’W, Nova Olinda do Norte, AM, Nov 1967 . MZUSP 7650 (3, 65.1-72.7 mm SL), 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 mm SL), rio Tapajós, Aveiro , c. 3°35’S 55°20’W, PA . MZUSP 9531 (2, 103.8- 141.4 mm SL), rio Tapajós , Alter do Chão, PA . MZUSP 9536 (2, 141.0- 162.4 mm SL), rio Nhamundá , PA, Aug 1968 . MZUSP 9547 (2, 137.3- 156.1 mm SL), rio Uatumã , São Sebastião do Uatumã, AM, Sep 1968 . MZUSP 15528 (1, 195.8 mm SL), 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 mm SL), rio Tapajós, Itaituba , c. 4°17’S 55°59’W, PA . MZUSP 31696 (1, 127.2 mm SL), rio Tefé, Jurupari , c. 3°22’S 64°43’W, Tefé, AM, Aug 1979 , M. Goulding. MZUSP 32539 (142, 109.2- 180.6 mm SL), rio Tapajós, São Luis , c. 4°27’S 56°15’W, PA, M. Goulding . MZUSP 32540 (12, 125.9- 164.3 mm SL), rio Tapajós , c. 4°17’S 55°59’W, Itaituba, PA . MZUSP 32541 (2, 117.3- 209.2 mm SL), rio Trombetas , c. 1°46’S 55°52’W, Oriximiná, PA . MZUSP 32542 (2 sk, 237, 140.6- 246.8 mm SL), rio Xingu, Belo Monte , c. 3°7’S 51°42’W, PA, M. Goulding . MZUSP 46010 (1 c&s, 11, 57.8-80.7 mm SL), rio Solimões , Coari, Ilha de Sorubim, AM . MZUSP 49179 (4, 122.0- 139.2 mm SL), rio Trombetas , c. 1°46’S 55°52’W, Oriximiná, PA . MZUSP 49181 (13, 122.3- 187.1 mm SL), rio Tapajós, Monte Cristo , c. 4°5’S 55°37’W, PA . MZUSP 49183 (13, 147.4- 200.5 mm SL), 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 mm SL), 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 mm SL), 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 mm SL), rio Tefé, Jurupari , c. 3°22’S 64°43’W, Tefé, AM . MZUSP 82256 (1, 186.6 mm SL), 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. Amazon basin ( Peru) : ANSP 181090 (1, 67.2 mm SL), 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 mm SL), near Iquitos, Peru, Aug 2006 , M. H. Sabaj et al. INHS 53720 (2, 59.0- 83.8 mm SL), rio Nanay drainage, Pampa Chica, 4.5 Km from Iquitos downtown, near Loreto, 3°45’9”S 73°17’0’’W, Aug 1999 . Essequibo basin ( Guyana): ANSP 175875 (1, 140.8 mm SL), Essequibo river, Maipuri , 4°45’43”N 58°45’52”W, Jan 1997 , W. Saul. ANSP 175876 (1, 82.1 mm SL), Essequibo river , 4°34’17”N 58°35’17”W, Maipuri, Jan 1997 , W. Saul et al. ANSP 179642 (1, 119.9 mm SL), 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 mm SL), Rupununi river, at sandcreek road crossing South Savannas ( RHL602 ), Apr 1961 , R. Lowe-McConnel. Orinoco basin ( Colombia) : AUM 28765 (4, 45.3-58.9 mm SL), río Manacias , río Meta basin, Puerto Gaitan, Colombia, X-1978 , J. S. Ramsey et al. Orinoco basin ( Venezuela) : ANSP 152870 (1, 43.9 mm SL), 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 mm SL), mouth of río Cuchivero , c. 7°40’N 65°57’W, Bolívar, Nov 1985 , B. Chernoff. ANSP 165493 (1, 146.7 mm SL), río Capanaparo, mouth of Caño Las Varitas, near San Fernando de 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 mm SL), Anzoategui, Soledad, l. Tineo , 8°11’25”N 63°28’20”W, Jan 1987 , M. Rodriguez & S. Richardson. ANSP 166597 (1, 70.9 mm SL), 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 mm SL), río Ventuari, Macuruco, San Fernando deAtabapo, 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 mm SL), río Ventuari , 4°6’55”N 66°45’52”W, May 2004 , Sabaj et al . ANSP 182796 (1, 101.3 mm SL), río Manapiare, San Juan de Manapiare , 5°26’12”N 66°6’45”W, Apr 2004 , M. H. Sabaj et al. CAS 58084 (1, 54.1 mm SL), río Orinoco , Delta Amacuro, Nov 1979 , J. N. Baskin & J. G. Lundberg. INHS 35082 (3, 90.5-95.4 mm SL), Laguna Castillero , 7°38’20”N 66°9’W, Bolívar, Jan 1988 , M. A. Rodriguez. MZUSP 105827 (1 sk, 144.7 mm SL), 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 mm SL), río San Jose, 10 km from mouth of San Jose and río Guariquito , Feb 1987 , W.L. Fink. No data: MZUSP 84553 (2 c&s, not measured) .

Diagnosis. Hassar orestis is diagnosed among its congeners by having the 1 st through 8 th (modally 3 rd) midlateral scute as the anteriormost with median thorn (vs. 9 th through 17 th), and tip of upper caudal-fin lobe usually darkened (vs. rarely or never darkened). Hassar orestis is further distinguished from H. affinis and H. gabiru by 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 orestis is yet distinguished from H. affinis by 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 th midlateral 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 orestis is also distinguished from H. gabiru by 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 3 and 4; morphometric data for type specimens in Table 4; type specimens 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 rd scute (range 1 st through 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 mm SL); 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.

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.

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 mm SL), or broad with continuous cartilaginous margin (in specimens <60 mm SL); 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 Type C (sensu Lundberg 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 superficialis and arrector ventralis muscles 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.

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 orestis is distributed in the Amazon, Orinoco and Essequibo river basins, in Bolivia, Brazil, Colombia, Guyana, Peru, and Venezuela, particularly in the Amazon lowlands ( Fig. 6 ). Hassar orestis is apparently absent in the upper Tapajós, middle and upper Xingu, and Tocantins basins.

Ecology. Specimens of Hassar orestis are 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. orestis develop 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 types specimens 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 Orestis Agass. 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 orestis was 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 types of Hassar orestis in overall morphology, and herein referred to as Hassar orestis . The Volta Grande rapids seem to be the upstream geographical limit of Hassar orestis in 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 Essequibo River in Guyana, as a valid species. The holotype of H. notospilus (FMNH 53184) is currently missing (Sabaj & Ferraris, 2003:461; Sabaj Pérez, pers. comm. 2011), but the specimen is clearly assignable to Hassar based 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 Essequibo River 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 Essequibo River and other localities, we agree with previous authors (e.g., Sabaj & Ferraris, 2003) in considering Hemidoras notospilus a junior synonym of Hassar orestis .

Fowler (1940) described Hassar ucayalensis from the río Ucayali, upper Amazon basin in Peru. Comparisons of juveniles and adults of H. orestis with the holotype of H. ucayalensis (SL= 6.89 cm; ANSP 68647) revealed only a difference in the number of secondary maxillary barbels (8-16 in H. orestis vs. 3 in the holotype of H. ucayalensis ). We believe that the reduced number of maxillary-barbel fimbriae might be best attributed to damaging and poor preservation of the holotype of H. ucayalensis . In the absence of additional differences that we could identify, the suspicion of Sabaj & Ferraris (2003) that H. ucayalensis is a junior synonym of H. orestis is corroborated. To avoid further taxonomic changes, we herein designated as lectotype of Hassar orestis a specimen from rio Iça in the upper Brazilian Amazon, near the Peruvian Amazon.

Figures

Fig. 9. (a) Lectotype of Hassar orestis, NMW45428, 66.8 mm SL, (b) paralectotype of Hassar orestis, NMW 45427, 206.0 mm SL; and (c) holotype of Hassar ucayalensis, ANSP 68647, 68.9 mm SL. Photos (b) and (c) by Mark Sabaj Pérez.

Fig. 10. Hassar orestis: (a) MZUSP 32542, 218.5 mm SL, rio Xingu at Belo Monte; (b) MZUSP 15528, 186.5 mm SL, rio Trombetas; (c) MZUSP 74680, 123.5 mm SL, rio Tefé; (d) MZUSP 6721, 79.4 mm SL, rio Negro.

Fig. 4. Gas bladders in ventral view of Hassar affinis (a-d): (a) MZUSP 90583, 54.4 mm SL; (b) MZUSP 74890, 85.9 mm SL; (c) MZUSP 43604, 228.0 mm SL; (d) ANSP 69392, 201.6 mm SL (holotype of Hassar woodi, photo by Mark Sabaj Pérez); Hassar gabiru (e-h): (e) MZUSP 87026, 69.0 mm SL; (f) MZUSP 94142, 137.6 mm SL; (g) INPA 31043, 122.5 mm SL; (h) MZUSP 94142, 128.6 mm SL; Hassar wilderi (i-l): (i) MZUSP 46016, 67.0 mm SL; (j) MZUSP 4857, 103.6 mm SL; (k) MZUSP 63148, 148.8 mm SL; (l) MZUSP 62998, 161.6 mm SL; Hassar orestis (m-p): (m) MZUSP 6991, 71.0 mm SL; (n) MZUSP 74680, 123.5 mm SL; (o) MZUSP 15512, 132.0 mm SL; (p) MZUSP 32542, 220.0 mm SL. Scale bars = 5 mm.

Fig. 11. Head and anterior portion of body in dorsal (above) and lateral (below) views of Hassar orestis, MZUSP 105827, 144.7 mm SL. AAR, anguloarticular; acf, anterior cranial fontanel; ANP, anterior nuchal plate; CLE, cleithrum; DEN, dentary; ENT, entopterygoid; EPO, epoccipital; FRO, frontal; INS, infranuchal scute; IO, infraorbital; IOP, interopercle; LET, lateral ethmoid; MAX, maxilla; MES, mesethmoid; MNP, middle nuchal plate; MTP, metapterygoid; Mr, Müllerian ramus; NAS, nasal; nf, nuchal foramina; OPE, opercle; PAL, autopalatine; pcf, posterior cranial fontanel; pEPO, epioccipital process; PNP, posterior nuchal plate; POP, preopercle; PTO, pterotic; QUA, quadrate; SCL, posttemporo-supracleithrum; SOC, parieto-supraoccipital; SPH, sphenotic. Scale bar = 5 mm.

Fig. 12. Schematic illustration of the hyoid and branchial arches of Hassar orestis, based on MZUSP 6991, 65.7 mm SL. ACH, anterior ceratohyal; BB, basibranchial; CB, ceratobranchial; DHH, dorsal hypohyal; EB, epibranchial; HB, hypobranchial; PB, pharyngobranchial; PCH, posterior ceratohyal; PTP, pharyngobranchial tooth plate; VHH, ventral hypohyal.

Fig. 13. Pectoral girdle in dorsal (left) and ventral (right) views of Hassar orestis, MZUSP 105827, 144.7 mm SL. Scale bar = 5 mm.

Fig. 14. Pelvic girdle in dorsal view of Hassar orestis, MZUSP 105827, 144.7 mm SL. Scale bar = 5 mm.

Fig. 15. Hassar orestis, MZUSP 103327, 106.5 mm SL, rio Jari, Monte Dourado, PA, photographed live.

Fig. 6. Distribution map of Hassar affinis (yellow triangles), H. gabiru (white diamonds), H. orestis (red circles), H. wilderi (orange pentamer). Stars represent type localities. Brown star indicates the type locality of Hassar ucayalensis, and pink star indicates that of Hassar woodi.