Sternarchorhynchus montanus, Santana & Vari, 2010

Santana, Carlos David De & Vari, Richard P., 2010, Electric fishes of the genus Sternarchorhynchus (Teleostei, Ostariophysi, Gymnotiformes); phylogenetic and revisionary studies, Zoological Journal of the Linnean Society 159 (1), pp. 223-371 : 324-330

STERNARCHORHYNCHUS MONTANUS SP. NOV.

( FIGS 58 , 59 ; TABLE 10)

Diagnosis: Sternarchorhynchus montanus is distinguished from congeners by the following combination of characters: a short gape that terminates posteriorly at, or slightly short of, the vertical through the anterior nares, the presence of a definite series of scales along the mid-dorsal region of the body, the lateral line that extends to a point one scale anterior of the base of the caudal fin, the presence of a more lightly coloured narrow band of mid-dorsal pigmentation on the head and mid-dorsal region of the body extending posteriorly to the origin of the electroreceptive filament and sometimes beyond that point, the distinctly dusky anal fin without a dark basal band, the possession of six to seven teeth on the premaxilla, six to seven teeth in the outer row of the dentary, 23–31 anterior unbranched anal-fin rays, 187–191 total anal-fin rays, 12–13 pectoral-fin rays, 16 precaudal vertebrae, the greatest body depth (7.5–13.0% of LEA), the preanal distance (9.5–10.2% of LEA), the prepectoral-fin distance (10.9–16.6% of LEA), the head length (16.3–17.0% of LEA), the distance from the anus to the anal-fin insertion (9.8–12.3% of HL), the caudal length (5.3–6.5% of LEA), the head depth at the eye (34.0–34.5% of HL), the head depth at the nape (53.5–55.7% of HL), the mouth length (4.3–5.2% of HL), the snout length (63.7–65.3% of HL), the distance from the posterior naris to the eye (54.4– 54.6% of HL), the eye diameter (4.0–4.3% of HL), the internarial distance (2.1–2.2% of HL), the interocular distance (5.3–5.4% of HL), the postocular distance (42.3–43.2% of HL), the height of the branchial opening (15.5–18.1% of HL), the pectoral-fin length (47.8–49.1% of HL), and the tail depth (21.1–21.7% of caudal length).

Description: Morphometric data for examined specimens in Table 10.

Lateral line extending posteriorly to point one scale anterior of base of caudal fin and absent on remainder of tail and on caudal fin. Snout elongate, compressed and curved ventrally. Mouth terminal with fleshy process arising from anterior limit of dentary. Rictus located along vertical slightly anterior of anterior naris. Anus and urogenital papilla located ventral to head, with position of openings variable; located within area delimited posteriorly by vertical through eye and anteriorly by vertical approximately four orbital diameters anterior of eye (secondary sexual dimorphism). Combined opening for anus and urogenital papilla ranging from circular to longitudinally ovoid.

Premaxilla with six to seven teeth (N = 2) apparent in whole specimens. Dentary with two tooth rows; outer row with six to seven teeth and inner row with two teeth (N = 2).

Branchiostegal rays five; with first to third rays narrow and elongate and fourth and fifth rays large and broad. Precaudal vertebrae 16 (13 anterior; three transitional; N = 2).

Pectoral-fin rays ii + 12–13 [12] (N = 2). Anal-fin origin located anterior to opercle. Anterior unbranched anal-fin rays 23–31 [23] (N = 2). Total anal-fin rays 187–191 [187] (N = 2). Scales above lateral line at midbody nine to 12 [9] (N = 2). Scales present along mid-dorsal region to origin of electroreceptive filament. Origin of midsaggital electroreceptive filament located approximately at 65% of TL. Filament extending to point one to two scales anterior of vertical through posterior terminus of base of anal fin. Tail compressed and short, ending in small, elongate caudal fin. Caudal-fin rays 12–16 (N = 2).

Coloration in alcohol: Overall coloration of head and body ranging from tan to dark brown. Snout with distinct dark band extending from slightly anterior of eye nearly to tip of snout. Ventrolateral surface of snout somewhat darker than ground coloration. Two dark regions on snout together delimit somewhat lighter intermediate band along lateral surface of anterior two-thirds of snout. Dorsal margin of dark pigmentation on snout forms lateral margin of narrow, lightly coloured stripe running along middorsal region of snout. More lightly coloured middorsal stripe continues onto and expands somewhat laterally on postocular portion of head. Expanded lightly coloured region slightly less apparent over posteriormost portion of head, but nonetheless continuous posteriorly with narrow, mid-dorsal stripe on body. Mid-dorsal stripe on body obvious, more so in darker holotype and extending from rear of head posteriorly to origin of electroreceptive filament or slightly beyond that point. Pectoral fin dusky, more so distally; very dark in overall more intensely pigmented holotype. Anal fin dusky with small, dark chromatophores overlying fin rays and inter-radial filaments. Intensity of pigmentation more pronounced along distal third to half of fin and forming obvious distal dark band. Caudal fin dark overall.

Distribution: Sternarchorhynchus montanus is known from two locations in the Río Marañon of Peru ( Fig. 58 ). It is uncertain where the two nontype specimens originated because they were secured from a dealer in the aquarium trade based in Iquitos, northeastern Peru. If the locality information associated with the nontypes is correct, it would extend the distribution of S. montanus to the Iquitos region. The two nontypes agree with the type series in all features that can be unequivocally determined, but both have regenerated tails, which makes it impossible to count the total number of anal-fin rays or determine morphometric values dependent on measurements taken to the end of the anal fin.

Secondary sexual dimorphism: Sternarchorhynchus montanus does not demonstrate the sexual dimorphism of the dentary and associated dentition present in some congeners. The male holotype is distinctly darker overall than the female paratype. A similar difference in coloration occurs between the nontype male and female. The female nontype, which is larger than the paratypic female, also has the posterior portion of the snout deeper than in the males. This specimen has the combined opening for the anus and urogenital papilla positioned approximately four orbital diameters anterior of the vertical through the eye contrary to the location of those combined openings approximately at the vertical through the eye in the nontype male of similar size and the male holotype and female paratype, both of which are of smaller sizes. This may indicate both ontogenetic and sexual dimorphism in the location of that opening comparable to that in congeners.

Etymology: The species name, montanus , from the Latin for mountains, refers to the type location of the type series in the foothills of the Andean Cordilleras. Material examined

Holotype: – PERU. Amazonas : Río Marañon , pongo above Borja , 35.5 km north-east Juan Velasco, Santa Maria de Nieva (4°27′36″S, 77°34″53′W), collected by N. K. Lujan, D. C. Werneke, D. C. Taphorn, A. S. Flecker, K. A. Capps, D. P. German, D. Osorio, 6.viii.2006; MUSM 31312 (226; formerly AUM 46270, in part).

Paratype: – PERU. Amazonas : Río Marañon , vicinity of Santa Maria de Nieva (Santa Maria de Nieva at 4°27′36″S, 77°34′53′W), collected by D. J. Stewart, 16.iv.1980; LACM 41741–44, 1 (258, female) .

Nontype specimens: – PERU. Amazonas: Río Amazonas, near Iquitos, 1 h above or below, purchased from aquarium fish dealer at Belen, 20.i.2004; UF uncatalogued, 2 (276–277, male and female).

STERNARCHORHYNCHUS MORMYRUS (STEINDACHNER)

( FIGS 58 , 60 , 61 ; TABLE 11)

Sternarchus mormyrus Steindachner, 1868a: 176 [description of species in abstract of primary description that appeared in Steindachner, 1868b]. Steindachner, 1868b: 253, pl. 1, fig. 3 [more detailed description following from Steindachner, 1868a; type locality reported as Brazil, Marabitanos (= Río Negro , north of Marabitanas at foot of Cocui mountains; Remarks); head and anterior portion of body of type illustrated]. – Eigenmann & Eigenmann, 1891: 62 [assignment to Sternarchorhynchus ]. – Ellis, 1913: 141 [placed as junior synonym of S. oxyrhynchus ]. – Fernández-Yépez, 1967: 18 [species resurrected from synonymy of S. oxyrhynchus ]. – Eschmeyer, 1998: 1122 [discussion as to which publication constitutes original description of species]. Sternarchorhynchus oxyrhynchus, Fowler, 1951: 431 [in part; citations of Sternarchus mormyrus and S. mormyrus , not other references].

Sternarchorhynchus mormyrus, Mago-Leccia, 1970: 76 [ Venezuela]. – Machado-Allison, 1987: 132 [llanos of Venezuela]. – Mago-Leccia, 1994: 37, fig. 54 [as valid species in listing of members of genus]. – Taphorn et al., 1997: 80 [ Venezuela]. – Campos-da- Paz, 2000: 528, fig. 2 [as valid species of Sternarchorhynchus in key to species of genus; syntype illustrated]. – Albert, 2003: 501 [in listing of members of genus]. – Lasso et al., 2004b: 142 [ Río Orinoco basin in Colombia and Venezuela]. – Lasso et al., 2004a: 181 [ Venezuela; Río Orinoco basin ]. – Crampton, 2007: 289 [widespread in Amazon and Orinoco basins]. – Triques, 2007: 125 [Amazon basin].

Diagnosis: Sternarchorhynchus mormyrus is distinguished from congeners by the following combination of characters: a short gape that terminates posteriorly at, or slightly short of, the vertical through the anterior nares, the absence of scales along the mid-dorsal region of the body as far posteriorly as the origin of the electroreceptive filament, and the possession of 222–245 anal-fin rays.

Description: Morphometric data for examined specimens in Table 11.

Lateral line extending posteriorly to base of caudal fin, but absent on fin. Snout elongate, compressed and curved ventrally. Mature males with wider snout than females ( de Santana & Crampton, 2006: 58). Mouth terminal and relatively small, with rictus located anterior to vertical through posterior naris. Anus and urogenital papilla located ventral to head, with position ontogenetically variable. Smaller examined specimens (c. 190 mm TL) with both structures positioned along vertical midway between rear of eye and Number of specimens indicated in parentheses. H, holotype; range includes nontype specimens.

Many specimens of S. mormyrus that served as basis for measurements had tails damaged as a consequence of apparent predation and various proportions could not be determined for these individuals. Sexually dimorphic features for S. retzeri are presented as two entries. First entry is data for all specimens other than sexually dimorphic mature males with information for sexually dimorphic male in second entry based on three specimens of 371–390 mm total length.

posterior border of opercle. Midsized specimens (c. 315 mm TL) with anus and urogenital papilla located along vertical one-third of distance between posterior margin of eye and posterior border of opercle. Largest examined specimens (c. 450–470 mm SL) with openings shifted distinctly anteriorly and positioned along verticals falling within region delimited posteriorly by vertical located slightly anterior to eye and anteriorly by vertical approximately one-third of distance between anterior margin of eye and tip of snout. Combined opening for anus and urogenital papillae circular to longitudinally ovoid in females, longitudinally ovoid in males.

Premaxilla with ten to 11 [ten in both syntypes] teeth and ten replacement teeth in cleared and stained specimen (122 TL) and with ten to 14 functional teeth apparent in whole specimens (N = 5). Sexual dimorphism in form of dentary and associated dentition present in some congeners not apparent in examined specimens. Dentary in cleared and stained specimen (122 TL) with one functional tooth row of nine curved conical teeth bordered medially by eight replacement teeth. Whole specimens with two tooth rows with 11–16 [13 in both syntypes] teeth in outer row and three to four [four in one syntype] teeth apparent in inner row (N = 4) .

Branchiostegal rays five; with first ray narrow and elongate, second and third rays somewhat wider, and fourth and fifth rays very large and broad with triangular ventral margins. Precaudal vertebrae 17–18 (four anterior; three to four transitional; N = 23).

Pectoral-fin rays ii + 13–15 (N = 23) [13 and 14 branched rays in syntypes]. Anal-fin origin located anterior to opercle. Anterior unbranched anal-fin rays 22–38 (N = 14). Total anal-fin rays 222–245 (N = 15) [226 in syntypes according to Steindachner (1868b: 254) but with 228 rays in smaller and 225 in larger syntypes; both specimens with regenerated tails]. Scales above lateral line at midbody nine to 12 [11 scales in syntypes] (N = 20). Scales along mid-dorsal line absent in many specimens along most of body anterior to origin of midsaggital electroreceptive filament. Larger specimens with areas lacking scales sometimes separated by scaled mid-dorsal patches, and with position and extent of unscaled regions variable both ontogenetically and within some population samples. Origin of midsaggital electroreceptive filament located approximately at 60% of TL. Filament extending posteriorly beyond vertical through posterior terminus of base of anal fin for distance of approximately four scales. Tail compressed and short, ending in small, elongate, pointed caudal fin. Caudal-fin rays 16–19 (N = 6) [16–17 in syntypes according to Steindachner (1868b: 254) but fins regenerated in both specimens].

Coloration in alcohol: Overall ground coloration light brown. Head in smaller specimens with scattered, small, dark chromatophores dorsally and on lateral surface of postocular region. More concentrated band of dark chromatophores located along dorsal region of snout in region from vertical through posterior naris to slightly posterior of eye. Dark pigmentation on head more obvious in larger individuals, with dark dorsal preorbital region often more obvious and sometimes extending anteriorly nearly to snout tip. Body in small specimens with light brown pigmentation overlain by relatively dense pattern of irregularly positioned, small, dark chromatophores. Larger individuals with overall coloration distinctly darker, but without any distinct pigmentation pattern.

Pectoral fin in smaller specimens hyaline to very slightly dusky distally. Distal pigmentation on fin increasingly pronounced in both extent and intensity ontogenetically. Largest individuals with pectoral fin sometimes nearly completely very darkly pigmented and with overall pigmentation distinctly darker than that present in juveniles. Anal fin in smallest examined individuals hyaline to very slightly pigmented distally, with distal pigmentation distinctly darker in largest specimens and sometimes covering distal twothirds of fin and forming irregular band. Caudal fin unpigmented.

Distribution: Sternarchorhynchus mormyrus is known from the mainstream of the Amazon River from Manaus in the central portions of the basin to the vicinity of Iquitos in north-eastern Peru, the Río Negro , and from the Río Orinoco basin in both Venezuela and south-eastern Colombia ( Fig. 58 ). A photograph that we examined shows a specimen that either S. mormyrus or a very similar undescribed species captured in the central portions of the Rio Madeira in the vicinity of Porto Velho. This location lies a considerable distance from the mainstream Amazon. Two questionable records of the species (see comments under Remarks below) would extend its distribution to the lower portions of the Amazon River basin.

The distribution of this species is the greatest in Sternarchorhynchus , but we did not identify any differences across that range (e.g. Orinoco versus Amazon basins) that justified the recognition of more than one species. Comparable broad ranges occur in some fish species that have been critically analysed across those basins within the Apteronotidae (e.g. Sternarchorhamphus muelleri , Campos-da-Paz, 1995: fig. 2) and other major groups in those ichthyofaunas (e.g. Siluriformes : Hoplosternum littorale, Reis, 1997 : fig. 4; Cetopsis coecutiens, Vari, Ferraris & de Pinna, 2005 : fig. 19. Cichlidae : Cichla ocellaris , Cichla temensis, Kullander & Ferreira, 2007 : figs 9, 75. Characidae : Roeboides affinis, de Lucena, 2007 : fig. 3).

Ecology: Juveniles of S. mormyrus live within várzea along the shores of the main river (C. D. de Santana, pers. observ.) whereas adults are inhabitants of main river channels ( Cox-Fernandes, Podos & Lundberg, 2004: supplemental information).

Electrical organ discharge: Crampton & Albert (2006: 688) briefly described the EOD in S. mormyrus as resembling the IR Type B pattern, but ‘in which the descending voltage curve has no, or only a very slight, outward inflection giving the waveform an asymmetrical aspect in the horizontal plane’. These authors consequently termed this EOD pattern as type C.

Secondary sexual dimorphism: de Santana & Crampton (2006: 58) remarked that S. mormyrus demonstrates sexual dimorphism in the form of the anterior portion of the neurocranium, with mature males having a wider snout than do conspecific females. Hilton & Cox-Fernandes (2006: 836) reported that S. mormyrus demonstrates sexual dimorphism of the lower jaw, with males having distended jaws relative to females. These authors also reported that males have many more teeth on that jaw than do females. We have not found such differences in the form of the lower jaw and dentary dentition in the material of S. mormyrus examined in this study.

Remarks: The two extant known syntypes of Sternarchus mormyrus (NMW 65336, 65345; Eschmeyer, 1998: 1122), both have regenerated tails makes it impossible to determine the total length and other distances and proportions that are a function of that measurement. The count of the anal-fin rays is also likely to be reduced as a consequence of that damage.

Steindachner (1868b: 253) reported the type locality of Sternarchus mormyrus as ‘Maribitanos’ without elaboration as to the river basin and country within which the collecting site was located. That site is undoubtedly Marabitanas, the type locality for various other lots of fishes deposited at NMW (e.g. Heros psittacus Heckel ) collected at ‘Rio-negro, nordlich von Marabitanas am Fusse des Berges Cocui’ (= Río Negro , north of Marabitanas at foot of Cocui mountains; Kullander, 2003: 637). Marabitanas is at approximately 00°58′N, 66°51′W in the region where Colombia, Brazil, and Venezuela border each other along the upper Río Negro.

Steindachner often published two accounts of species that he described as new. One paper was typically a brief abstract in the Anzeiger de Akademie der Wissenschaften, Wien with the name of the species and a brief listing of certain diagnostic characters. He complimented these brief initial accounts with a second more detailed account that was often accompanied by detailed illustrations. These accounts were typically published in the Sitzungsberichte der Akademie der Wissenschaften, Matematicsh- Naturwissenschafrliche Classe, Wien, although on occasion in other outlets. In the case of Sternarchus mormyrus , the Sternarchorhynchus mormyrus of this study, previous authors (e.g. Mago-Leccia, 1994; Campos-da-Paz, 2000) understandably assumed that the detailed description with an associated illustration of the head and anterior portion of the body of a syntype ( Steindachner, 1868b) constituted the formal description. In this instance the abstract ( Steindachner, 1868a) was published first ( Eschmeyer, 1998: 1122) and, thus, constitutes the formal original description of Sternarchus mormyrus .

Eigenmann & Bean (1907) proposed that S. curvirostris was a likely senior synonym of S. mormyrus . Sternarchorhynchus mormyrus and S. curvirostris were, in turn, placed as junior synonyms of S. oxyrhynchus by Ellis (1913: 141), who considered the latter species to be a monotypic, morphologically highly variable form. Fernández-Yépez (1967: 18) resurrected S. mormyrus and S. curvirostris from synonymy on the basis of various external features of the head. Based on the illustration provided by Fernández-Yépez (1967: 19), the material that he reported as S. curvirostris differed from that species in various details and is likely to be another species. It is also questionable whether Fernández-Yépez had material of S. mormyrus at hand given the differences between the illustrated specimen and S. mormyrus , most notably in the form of the snout and position of the anus and urogenital papilla. That question notwithstanding, the practice of recognizing S. mormyrus as a distinct species was continued by Mago-Leccia (1994: 37) and Campos-da-Paz (2000: 528). Our results confirm the distinctiveness of S. mormyrus . Indeed it is one of the more easily recognized species within Sternarchorhynchus .

Eigenmann & Bean (1907: 666) reported on specimens of what they identified as S. mormyrus from along the Amazon River in the region between Manaus and Pará (= Belém). Although S. mormyrus does occur in that region, those specimens had 191 to 194 anal-fin rays, a range distinctly lower than the 222 to 245 rays present in S. mormyrus . Examination of the specimens (USNM 52542) that served as the basis for that record has shown them to be S. starksi .

The easternmost records for S. mormyrus within the Amazon basin in this study ( Fig. 58 ) are based on two specimens (USNM 373026, USNM 373050) lacking portions of their tails. This damage renders a definitive identification problematic, but these specimens are assigned to S. mormyrus based on their correspondence to that species in other features including morphometrics of the head, overall head and body form, and coloration.

Material examined

BRAZIL. Amazonas: Marabitanas (approximately 00°58′N, 66°51′W), NMW 65345, approximately 315 [syntype of Sternarchus mormyrus , tail regenerated]; NMW 65336, 384 [syntype of Sternarchus mormyrus , tail regenerated]. Rio Solimões , Ilha do Careiro, Lago Juanico; INPA 4899, 2 (378–413), INPA 27473, 3 (243–251), INPA 27474, 1 (214); INPA 4900, 1 (505). Rio Solimões , Ilha da Machantaria, INPA 17608, 1 (342), INPA 17609, 3 (310–350), INPA 27470, 1 (300). Rio Solimões , Paraná do Xiborena; INPA 17610, 1 (240), INPA 27475, 1 (270), INPA 27746, 1 (382). Rio Solimões , Paraná do Cuarí; INPA 17611, 1 (180). Rio Japurá , mouth of Lago Caxinguba; INPA 18295, 1 (243). Rio Purus, Beruri ; INPA 27477, 1 (365). Lago Manacapuru (3°06′S, 61°30′W); MCZ 34338, 1 (250). Rio Amazonas, 28.5 km below Manaus (3°05′33″S, 59°46′27″W); USNM 306843, 2 (1 CS, 119–122); USNM 229916, 1 (133); USNM 375479, 1 (315). Rio Jutaí , near Zinho (2°57′40″S 67°00′48″W); MZUSP 55855, 1 (257). Rio Amazonas, Parintins (2°38′S, 56°46′W); MZUSP 79856, 1 (105). Rio Uaupés (2°55′S 69°38′W); MZUSP 91647, 1 (410). Rio Negro , 5.4 km below Unini (1°41′41″S 61°29′19″W); MZUSP 55852, 1 (279). Rio Negro , below Daraá (approximately 0°30′S, 64°40′W); MZUSP 32202, 2, 335–379. Rio Negro , at Manaus (3°06′S, 60°00′W); MCZ 9347, 1 (258).

COLOMBIA. Río Orinoco basin , Río Meta, no specified locality; IAVHP 2674; 1 (520).

PERU. Amazonas: Río Marañon , pongo above Borja, 35.5 km north-east of Juan Velasco at Santa Maria de Neiva (approximately 4°50′S, 77°51′W); AUM 47285, 1 (305; formerly AUM 46270, in part). Loreto: Río Amazonas, vicinity of Iquitos, upstream and downstream of mouth Río Itaya (3°40′36″S, 73°14′37″W); ANSP 182583, 1 (190).

VENEZUELA. Apure: Río Guariquito at confluence with Río Orinoco ; MBUCV 15711, 1 (300). Río Apure, in front of mouth of Caño Manglar (approximately 7°52′N, 67°36′W); MBUCV 20670, 1 (522). Río Matyure , just south of village of Achaguas (7°45′N, 68°15′W); CU 72165, 1 (148). Delta Amacuro : Caño at mouth of Anabata into Río Orinoco , north of Isla Portuguesa (approximately 8°37′12″N, 61°47′33″W); CU 80960, 2 (252–275). Río Orinoco , south of Isla Portuguesa, 116 nautical miles (= 214.6 km) upstream from sea buoy (approximately 8°37′N, 61°49′W); LACM 43044–5, 1 (420). Río Orinoco , on north shore at Isla Portuguesa (approximately 8°37′N, 61°49′W); LACM 43295–84, 2 (261–273). Río Orinoco , in front of Isla Iguana; MBUCV 10512, 1 (200). Río Orinoco , in front of Isla Tres Caños (8°40′N, 62°00″W; MBUCV 10885, 1 (239), MBUCV 12081, 1 (229). Río Orinoco , shallow river downstream from buoy 82, near mouth of small caño (8°28′24″N, 61°17′12″W); USNM 228646, 1 (264). Río Orinoco (8°40′12″N, 62°00′00″W); USNM 228875, 1 (495). Guárico: Caño Casi Seco, 42 km east of Guayabal (8°01′67″N, 67°07′50″W); MCNG 14427, 1 (110).

The following material is tentatively identified as S. mormyrus (comments under Remarks above):

BRAZIL. Pará: Rio Amazonas, between Almerim and Gurupá (01°28′38″S, 52°04′00″W); USNM 373026, 1 (261). Rio Amazonas, 58.5 km below Jurutí, 21.1 km above Óbidos (1°55′56″S, 55°40′58″W); USNM 373050, 1 (235).

Figures

Figure 58. Map of central and northern South America showing geographical distribution of Sternarchorhynchus mesensis, Sternarchorhynchus montanus sp. nov. (1 = holotype locality), and Sternarchorhynchus mormyrus (some symbols represent more than one locality and/or lot of specimens).

Figure 59. Sternarchorhynchus montanus sp. nov., holotype, male, 226 mm total length, MUSM 31312; Peru, Amazonas, Río Marañon.

Figure 60. Sternarchorhynchus mormyrus, illustration of head of one of the syntypes (from Steindachner, 1868b: table 1, fig. 3). Figure reversed from original orientation.

Figure 61. Sternarchorhynchus mormyrus, male, 315 mm total length, USNM 375479; Brazil, Amazonas, Rio Amazonas.