Taxonomic revision of thorny catfish genus Hassar (Siluriformes: Doradidae)

The genus Hassar (Doradidae) is diagnosed by a single exclusive feature: basioccipital with ventral ring-like arch surrounding aorta; and by the combination of several non-exclusive characters, including dark blotch in distal half of anterior branched rays of dorsal fin, and anteriormost postinfranuchal scutes reduced in size. Three nominal species are recognized and redescribed in Hassar: H. orestis from the Orinoco, Essequibo and Amazonas basins, excluding Tocantins and middle to upper Xingu drainages; H. wilderi from Tocantins; and H. affinis from northeastern Brazil, including Turiaçu, Pindaré-Mearim, Itapecuru and Parnaíba drainages. The nominal Hemidoras notospilus and Hassar ucayalensis are recognized as junior synonyms of Hassar orestis; Hassar woodi is considered a junior synonym of H. affinis; Hassar iheringi is recognized as a junior synonym of H. wilderi, and its type locality as originally reported is considered incorrect. A fourth new species, Hassar gabiru, is described from middle to upper Xingu river basin. Hassar is considered to be the sister taxon of Anduzedoras + Leptodoras. A detailed anatomical description and discussion of the phylogenetic relationships of Hassar among fimbriate-barbel doradids are provided.

Five additional species were added to Hassar between 1912 described Hemidoras notospilus from the Essequibo River, Guyana, and subsequently transferred this species to Hassar . Fowler (1940) described Hassar ucayalensis based on a single juvenile from the río Ucayali, Peru, and Fowler (1941) described Hassar woodi and H. iheringi considering both from the rio Parnaíba, Brazil. Finally,  described Hassar praelongus from the rio Negro, Brazil. None of these species were considered valid in Hassar by Sabaj & Ferraris (2003), who treated H. notospilus as a junior synonym of Hassar orestis, H. ucayalensis as a questionable junior synonym of H. orestis, H. woodi and H. iheringi as junior synonyms of H. affinis, and H. praelongus as a valid species in the genus Leptodoras Boulenger, 1898. Sabaj & Ferraris (2003) recognized three valid species of Hassar: H. affinis in the Parnaíba basin, H. orestis in the Amazon, Orinoco and Essequibo basins, and H. wilderi in the Tocantins basin. Higuchi (1992) provided the first cladistic hypothesis of phylogenetic relationships among genera of Doradidae, and his morphological analysis recovered Hassar as sister to Opsodoras + Hemidoras. That same relationship was hypothesized by Moyer et al. (2004) in a parsimony analysis of molecular data combining sequences of mitochondrial genes 12S and 16S rRNA and nuclear gene elongation factor-1 alpha fig. 9A). However, their maximum likelihood analysis of the same sequences placed Hassar as sister to Nemadoras. Sabaj (2002), in a cladistic analysis of the relationships among species of Leptodoras, recovered Hassar as sister to Anduzedoras + Leptodoras, and alternatively but less parsimoniously, as sister to Hemidoras (Opsodoras was not considered). Birindelli (2006Birindelli ( , 2010 studied the phylogenetic relationships among most genera and species of Doradidae, and diagnosed Hassar based on internal and external characteristics. Birindelli (2006Birindelli ( , 2010 also recovered Hassar as sister to Anduzedoras + Leptodoras, and distinguished its three valid species (H. affinis, H. orestis, H. wilderi) according to the ratio of body depth to standard length, and coloration of the dorsal fin.
In this paper we redefine the genus Hassar by unique and non-exclusive characters, redescribe H. affinis, H. orestis, H. wilderi, and describe a new species from the middle to upper rio Xingu. We also discuss the phylogenetic relationships of Hassar among fimbriate-barbel doradids.

Material and Methods
Measurements were made preferentially on the left side of the body using digital calipers (0.1 mm) and a stereomicroscope. Measurements follow Sabaj (2005), with the following additions: prepelvic distance (horizontal distance from snout tip to base of first pelvic-fin ray); preanal distance (horizontal distance from snout tip to base of first anal-fin ray); body depth at analfin origin (vertical distance between anal-fin origin and dorsal margin of adipose fin); length of first branched ray of dorsal fin; length of dorsal-fin base; head width at operculum (transverse distance between the dorsalmost opening of opercula); body width at nuchal shield (minimum transverse distance between lateral margins of nuchal shield). All measurements were treated as percentages of standard length (SL), except for subunits of head, treated as percentages of head length (HL), and depth of 10 th midlateral scute, treated as percentage of body depth at 10 th midlateral scute (BD10). All measurements in material examined section refer to standard length in millimeters.
Osteological examinations were made on dry skeletons (sk), cleared and stained (c&s) material prepared according to Taylor & Van Dyke (1985) and Song & Parenti (1995), and radiographs taken with a Faxitron MX-20 digital x-ray system. Osteological terminology follows Weitzman (1962) with exceptions noted by Birindelli & Sabaj Pérez (in press); gas bladder terminology follows Birindelli et al. (2009). Institutional abbreviations are: fontanel relatively large, extending posteriorly into the parietosupraoccipital; 7) first infraorbital long and slender, with dilated anterior extremity, articulating with the lateral border of mesethmoid; 8) ossified and extremely well-developed epioccipital process, sutured to the posterior nuchal plate; 9) less than 10 premaxillary teeth; 10) less than 20 dentary teeth; 11) well-developed nuchal foramina; 12) reduced anterior nuchal plate, enclosed by the posterior margin of the parietosupraoccipital and anterior margin of the middle nuchal plate; 13) 30 to 34 midlateral scutes on each side of body. See Discussion for additional notes on the aforementioned diagnostic features.
Etymology. Eigenmann & Eigenmann (1888) did not specify the origin of Hassar, but it possibly refers to the name commonly applied to certain catfishes in Guyana, such as Hoplosternum littorale or Hypostomus watawata . ( Description. Morphometric data are summarized in Tables 1  and 2; type specimens illustrated in Fig. 2; additional specimens in Fig. 3. Largest specimen examined 201.6 mm SL (ANSP 69392, holotype of Hassar woodi); reported to 213 mm SL (Menezes, 1949). 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 from 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 Three pairs of barbels (maxillary, inner and outer mental), all fimbriate. Maxillary barbel usually reaching base of first pectoral-fin ray; with 7 to 16 (mode 11, n=47) 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.

Hassar affinis
Gill rakers small on first gill arch, absent 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=17) 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 13 th scute (range 12 th through 17 th , n=19); medial thorn and dorsal and ventral wings gradually increasing in size posteriorly; scutes with serrated posterior margins and overlapping on the last third of the body.
Gas bladder (Fig. 4) moderately large, cordiform. Gas bladder walls entirely smooth in small specimens (up to 50 mm SL). Large specimens have only two short rounded diverticula on each side of anterior chamber; in the largest specimen examined (ANSP 69392, 201.6 mm SL) a third pair of diverticula are present at middle of lateral margin of posterior chambers; lateral diverticula rarely branched (only in large specimens). Gas bladder rounded posteriorly, not extended into terminal diverticula.
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. First two (or rarely three) branched dorsal-fin rays and membranes distally darkened (distalmost fifth to third of fin-ray length), dark pigment extending to tips of rays and membranes (except in some large specimens with dorsal fin uniformely tan). Tip of upper caudal-fin lobe not conspicuously darkened. Soares (2005) noted the upper sides and flanks yellowish-gray and ventral surfaces white in a live specimen of Hassar affinis.
Ecology. Menezes (1949) examined the diet of 25 specimens (48-180 mm SL) collected in lentic and lotic environments of the rio Parnaíba, Piauí, and observed that H. affinis feeds primarily on insects and, to a lesser extent, on crustaceans and plant residue. Fish remains were found in the intestine of a large examined specimen (213 mm SL). According to Soares (2005) Hassar affinis inhabits igarapés, lakes and rivers, and has an omnivorous diet.
Remarks. Steindachner (1881) distinguished Hassar affinis by having 18 to 20 midlateral scutes with thorns (vs. more in H. orestis), and a "slightly darker coloration on the superior marginal portion of the first rays of [dorsal] fin" (vs. a "sharply defined black mark" on the dorsal fin in H. orestis). Both characters are corroborated herein as consistent differences between the two species. Fowler (1941a) reported a single juvenile specimen (ANSP 69396, 76 mm SL) as collected in Fortaleza (Ceará). However, since no large drainage exists between Fortaleza and rio Parnaíba, Sabaj (2002) suggested that that specimen was probably obtained in a fish market, making it unfeasible to substantiate its origin.

Diagnosis.
Hassar gabiru is distinguished from H. orestis and H. wilderi by having two weakly-branched diverticula restricted to each side of anterior chamber of gas bladder (rarely one extra pair on posterior chambers) (vs. gas bladder with many well-branched diverticula along margins of entire bladder); and gas bladder rounded posteriorly (vs. gas bladder triangular posteriorly, each posterior chamber extended posteriorly into a short terminal diverticulum sharing medial septum with its pair Dorsal profile of head rising moderately, evenly (usually in smaller specimens) or slightly 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 weakly developed adipose eyelid in juveniles and adults, extended slightly beyond anterior and posterior limits of eye. Eyes positioned about half way between tip of snout and dorsalfin origin.
Three pairs of barbels (maxillary, inner and outer mental), all fimbriate. Maxillary barbel usually reaching base of first pectoral-fin ray; with 10 to 14 (mode 12, n=13) 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 small on first gill arch, absent 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.
Gas bladder (Fig. 4) moderately large, cordiform. Gas bladder walls entirely smooth in small specimens (up to 50 mm SL). Large specimens have only two short weaklybranched diverticula on each side of anterior chamber; in the largest specimens examined a third pair of diverticula are present at middle of lateral margin of posterior chambers. Gas bladder rounded posteriorly, not extended into terminal diverticula.
Osteology. Osteology generally similar to that described for Hassar orestis, excepting differences as follows. Total vertebrae 35 (n=1), vertebrae 6-13 bearing ribs. Eight (n=1) dorsal-fin pterygiophores, 10 (n=1) pelvic-fin pterygiophores; 12 (n=2) dorsal and 12 (n=1) ventral caudal-fin procurrent rays. All examined specimens with hypural fusion pattern PH; HY 1+2; HY 3+4; HY 5, and with complete ossification of sutural joint at junction of sphenotic, parieto-supraoccipital and frontal.  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 not conspicuously darkened.
In life, ground color yellowish or greenish laterally and white ventrally; lower lip pinkish; eye silvery ( Fig. 8).
Distribution. Hassar gabiru occurs in the middle to upper Xingu river basin (Fig. 6), and is apparently endemic to the Xingu basin above the rapids of Volta Grande, near Altamira.
Ecology. Like its congeners, Hassar gabiru was collected usually in swift water over sand beaches at night. Camargo (2009) considered that specimens of Hassar orestis (=Hassar gabiru) collected at the Volta Grande rapids have preference for benthic invertebrates and detritus.
Etymology. Named in honor of Leandro Melo de Sousa, known to his friends as "Gabiru", for his many contributions to the understanding of the Doradidae, including his MSc and PhD dissertations (Sousa & Rapp Py-Daniel, 2005;Sousa, 2010). Leandro also helped to collect part of the type series of the new species. Treated as a noun in apposition.
Remarks. Specimens of Hassar from the rio Xingu above the rapids of Volta Grande are distinct from the specimens below the rapids (including the area near Belo Monte) in overall body shape and gas bladder morphology, and are similar to the specimens from the upper Xingu river basin, herein referred to as the new species Hassar gabiru. This indicates that the Volta Grande rapids impose a distributional limit between H. gabiru and H. orestis. The identity of the specimens cited by Camargo et al. (2004), Camargo (2009) and Camargo & Giarrizzo (2009) were not verified by us. However, specimens collected at the rapids of Volta Grande or upstream (putatively including rio Bacajá) are likely to be Hassar gabiru. 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). Tables 3  and 4; morphometric data for type specimens in Table 4; type specimens illustrated in Fig. 9, additional specimens in Fig. 10. Largest specimen examined 246.8 mm SL (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.

Description. Morphometric data are summarized in
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.
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 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.
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.  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  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 &

Diagnosis.
Hassar wilderi is distinguished from H. orestis by having 9 th through 14 th , modally 12 th , midlateral scute as the anteriormost with median thorn (vs. 1 st through 8 th , modally 3 rd ), and tip of upper caudal-fin lobe rarely darkened (vs. usually darkened). Hassar wilderi is distinguished from H. affinis and H. gabiru by having gas bladder with many well-branched diverticula on margins of the entire bladder (vs. gas bladder with two rounded or weakly-branched diverticula restricted to each side of anterior chamber of the gas 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) (Fig. 4). Hassar wilderi is further distinguished from Hassar affinis by having the first branched dorsal-fin rays and membranes pale (vs. first branched dorsal-fin rays and membranes distally darkened). Tables 3  and 4; morphometric data for type specimens in Table 4; type and non-type specimens illustrated in Fig. 16. Largest specimen examined 188.4 mm SL (MZUSP 52394). Dorsal profile of head rising moderately, evenly (usually in smaller specimens) or slightly convex (especially in larger specimens) from snout tip to anterior margin of orbit, and relatively straight from that point to the 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 that 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 weakly developed adipose eyelid in juveniles (SL < 14 cm), extended slightly beyond anterior and posterior limits of eye, and moderately developed in adults (SL >14 cm), extended slightly further anteriorly than in juveniles. Eyes positioned about half way between tip of snout and dorsal-fin origin.

Description. Morphometric data are summarized in
Three pairs of barbels (maxillary, inner and outer mental), all fimbriate. Maxillary barbel usually reaching base of first pectoral-fin ray; with 8 to 13 (mode 10, n=66) 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 small on first gill arch, absent 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=60) 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 Table 2. Morphometric data for type specimens of the Hassar affinis and H. gabiru. SD = standard deviation. starting at 12 th scute (range 9 th through 14 th , n=60); medial thorn and dorsal and ventral wings gradually increasing in size posteriorly; scutes with serrated posterior margin and overlapping on last third of body.
Gas bladder (Fig. 4) moderately large, cordiform. Bundles of diverticula present along the anterior, lateral, and posterior margins of the entire bladder in small specimens (< 50 mm SL); diverticula become thinner and more branched in larger specimens. Gas bladder triangular posteriorly, each posterior chamber extended into a short terminal diverticulum sharing medial septum with its pair and possessing smaller lateral diverticula.
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 only rarely darkened. In life, ground color yellowish or greenish laterally and white ventrally; lower lip pinkish. Eye silvery, distinctly contrasted with pale surrounding adipose tissue.
Ecology. Like its congeners, specimens of Hassar wilderi are usually collected over sandy beaches (substrate sometimes with fine gravel or muddy), and often in the main channel of large rivers. Santos et al. (1984) stated that individuals of H. wilderi reach sexual maturity with approximately 15 cm long. Eggs are deposited between November and January.
Etymology. Named in honor of B. G. Wilder, who sent the collection made by C. F. Hartt in Brazil to C. H. Eigenmann for identification. The catfishes of this collection were then transmitted to E. M. Kindle for final determination. According to Kindle (1895: 249), the collection contained 19 genera and 27 species, including two new species: Hassar wilderi and Hemiancistrus longipinnis (= Baryancistrus longipinnis). Fowler's (1941a) description of Hassar iheringi, three of the four type specimens (including the holotype) were collected in "Rio Parnahyba, Terezina, Piauhy". Examination of these specimens, however, revealed that they possess some characters that are absent in specimens from northeastern Brazilian drainages, which are herein referred to as H. affinis. Those characters are: many thin, branched lateral diverticula on entire margin of gas bladder, dark blotch over the median portion of the first branched dorsal-fin rays, first five postinfranuchal scutes developed with two posteriorly directed thorns, and relatively deep body (see Tables 1 to 4). Actually, these features are present in H. wilderi, who seems to occur exclusively in the Tocantins basin according to the specimens we examined. This indicates that the locality of three type specimens of H. iheringi referred by Fowler (1941a) is probably wrong, and that those specimens were probably collected in the Tocantins basin. Similar locality errors have already been recorded by Vari (1995), Vari & Harold (2001), and Castro & Vari (2004). We therefore consider that H. iheringi is a junior synonym of H. wilderi, and that Fowler (1941a)'s referred locality is wrong.

Remarks. According to
Hassar wilderi was described based on four specimens first deposited in the Cornell University (under catalogue numbers CU 1703-1705, plus one uncatalogued specimen), which were then transferred to the Indiana University to be identified by Eigenmann (catalogued as IU 5120).  monograph listed the specimens as "I.U.M. 5120, types, 162 and 207 mm" (measurements given in TL), and included an illustration of the smallest specimen  pl. 22, fig. 2). Those specimens were subsequently transferred to the