Sternarchorhynchus retzeri, 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 : 334-340

STERNARCHORHYNCHUS RETZERI SP. NOV.

( FIGS 63–65 ; TABLE 11)

Sternarchorhynchus cf. roseni – Crampton, 2007: 320, fig. 11.13c [sexual dimorphism in form of anterior portion of dentary].

Diagnosis: Sternarchorhynchus retzeri 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 posteriorly to the base of the caudal fin, the presence of a narrow, more lightly coloured 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 distinct band of dark pigmentation along the distal third to half of most of the anal fin and covering most of the posterior rays on that fin, the possession of eight to 11 teeth on the premaxilla, five to nine teeth in the outer tooth row of the dentary, one to two teeth in the inner tooth row of the dentary, 17–25 anterior unbranched anal-fin rays, 198–225 total anal-fin rays, 14–18 caudal-fin rays, 15 precaudal vertebrae, the greatest body depth (8.3– 10.1% of LEA), the preanal distance (13.0–15.2% of LEA), the caudal length (7.1–10.3% of LEA), the head width (15.9–18.7% of HL), the head depth at the eye (21.4–27.7% of HL), the head depth at the nape (34.1– 41.8% of HL), the snout length (65.4–71.2% of HL), the distance from the posterior naris to the eye (57.3– 74.0% of HL), the distance from the posterior naris to the snout (5.7–7.0% of HL), the eye diameter (2.5– 3.4% of HL), the postocular distance (31.6–34.9% of HL), the height of the branchial opening (10.0–12.5% of HL), the pectoral-fin length (34.4–39.1% of HL), and the tail depth (15.3–15.8% of caudal length).

Description: Morphometric data for holotype and paratypes in Table 11.

Lateral line extending to base of caudal fin, but absent on fin. Snout elongate, compressed and straight to very slightly curved ventrally distally. Posterior naris closer to tip of snout than to anterior margin of eye. Branchial opening restricted and situated slightly anterior to vertical through pectoral-fin origin. Location of anus and urogenital papilla ontogenetically variable and apparently sexually dimorphic. Openings in smaller individuals positioned along vertical located slight distance posterior of vertical through rear margin of orbit. Anus and urogenital papilla located at vertical slightly anterior of anterior margin of orbit in mature females and also in mature males lacking patch of large teeth at anterior of dentary. Males with patch of large teeth at anterior of dentary with anus and urogenital papilla positioned further anteriorly approximately at vertical one-third of distance between anterior margin of eye and tip of snout. Combined opening relatively rounded in juveniles and somewhat to distinctly horizontally elongate in larger specimens.

Premaxilla of small size, somewhat rounded, with eight to 11 teeth (N = 3). Dentary sexually dimorphic. Dentary in mature males extended further anteriorly than in females and juveniles and with anterior portion widened transversely into bulbous structure rounded from dorsal view and bearing series of enlarged, posteriorly recurved teeth on dorsal surface. Dentary bearing two irregular tooth rows with approximately five to nine teeth present in outer row and one to two in inner row (N = 3). Mouth terminal with rictus located anterior to vertical through posterior naris.

Branchiostegal rays five; with first to third rays relatively narrow and elongate and fourth and fifth branchiostegals large and broad. Precaudal vertebrae 16 (12–13 anterior; three to four transitional, N = 10).

Pectoral-fin rays ii + 12–15 [ii + 14] (N = 20). Analfin origin located slightly posterior of vertical through anterior margin of opercle. Anterior unbranched anal-fin rays 17–27 [27] (N = 12). Total anal-fin rays 198–225 [225] (N = 14); number of rays apparently increases ontogenetically based on correlation between increased body length and greater numbers of rays in examined samples. Scales above lateral line at midbody ten to 11 [10] (N = 20). Scales along mid-dorsal region of body readily apparent. Origin of midsaggital electroreceptive filament located approximately at 67% of TL. Filament typically extending posteriorly to vertical through posterior terminus of base of anal fin. Tail compressed and of moderate length, ending in small and elongate caudal fin. Caudal-fin rays 14–18 (N = 13).

Coloration in alcohol: Overall ground coloration ranging from light to dark brown. Head and body with dark chromatophores relatively densely scattered over surfaces. Relative size of chromatophores and intensity of pigmentation greater in overall darker specimens. Snout with variably distinct, narrow band of pigmentation somewhat darker than ground coloration extending anteriorly from region slightly forward of orbit to, or slightly short of, anterior portion of snout. Band of dark pigmentation on snout borders narrow, lightly coloured, mid-dorsal band on head; lightly pigmented band apparent even in overall darkly pigmented specimens. Ventral margin of snout somewhat darker than lateral surface of snout in some specimens. Body pigmentation slightly darker dorsally, but with mid-dorsal, more lightly coloured stripe extending from stripe on head posteriorly onto basal portions of electroreceptive filament and then to varying degrees further posteriorly.

Pectoral fin coloration ranging from dusky to distinctly dark, with pigmentation more pronounced over fin rays and distally. Anal fin with distinct band of dark pigmentation along distal third to half of fin along most of its length, but with dark pigmentation covering nearly all of shorter fin rays posteriorly. Caudal-fin rays dark.

Distribution: Sternarchorhynchus retzeri is broadly distributed across the Amazon basin from the Rio Iça basin in the western portions of Amazonas, Brazil, to the Rio Trombetas in Pará, Brazil ( Fig. 63 ).

Electrical organ discharge: Crampton & Albert (2006: 688) reported that S. retzeri (identified by those authors as S. cf. roseni ) had an EOD resembling their type B, 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’. In light of this difference they proposed that it be separated as a type C EOD pattern.

Secondary sexual dimorphism: Specimens of S. retzeri examined in this study demonstrate a striking sexual dimorphism in the form of the dentary and in the position of the anus and urogenital opening. At least some males have the dentary extended further anteriorly and widened transversely into a dorsally bulbous structure that is distinctly rounded from dorsal view and bears a series of enlarged, posteriorly recurved teeth ( Crampton, 2007: fig. 11.13c; species identified therein as S. cf. roseni ). Juveniles and adults without these elaborations instead have the anus and urogenital opening positioned approximately along the vertical through the eye. Males as evidenced by the presence of a well-developed patch of teeth on the anterior portion of the dentary have these structures instead significantly shifted anteriorly and positioned within the region delimited by the verticals falling one-quarter to one-third of the distance from the anterior margin of the orbit to the tip of the snout.

Geographical variation: Nearly all specimens of S. retzeri examined in this study have the termination of the electroreceptive filament located at the vertical through the posterior terminus of the base of the anal fin. One possible specimen of the species captured in the Rio Negro (FMNH 115484), has the filament extending somewhat more posteriorly for a distance of about four scales beyond the vertical through the posterior termination of the base of the anal fin. This specimen is a mature male as evidenced by the gonads, but has the anus and urogenital papilla anteriorly positioned along a vertical approximately onethird of the distance between the anterior margin of the orbit and the tip of the snout. This anterior position of the anus and urogenital papilla occurs elsewhere in S. retzeri only in mature males with a distinct batch of enlarged dentition on the anterior portion of the dentary. The specimen from the Rio Negro may represent a male of this species without such modifications of the anterior portions of the dentary and associated dentition, a situation that occurs in males of some congeners. Additional samples are necessary to determine whether it represents a geographical variant, possible differential expression of secondary sexual characters in males because of seasonality in the presence of such dentary modifications, or an undescribed species.

Etymology: The specific name, retzeri , is in honour of Michael Retzer of the Illinois Natural History Survey who provided invaluable assistance through the years to both authors in the course of this and other research projects.

Material examined

Holotype: – BRAZIL. Amazonas : Rio Tefé, Toco Preto, Tefé (3°47′19″S, 64°59′54″W), collected by W. G. R. Crampton, 25.x.1999; MCP 41636, 1 (372).

Paratypes: – BRAZIL. Amazonas : Rio Tefé, Toco Preto, Tefé (3°47′19″S, 64°59′54″W), collected by W. G. R. Crampton, 22–25.x.1999; MCP 41635 , 10 (281–390).

Nontype specimens: – BRAZIL. Amazonas: FMNH 115481, 1 (279), FMNH 115504, 1 (222); Río Iça, between Paraná do Curumim and Rio Solimões , between towns of Betânia and São Antônio do Iça (3°8′48″S, 68°02′07″W). FMNH 115484, 1 (327); Rio Negro between Paraná Cantagalo and Paraná Onças, between São Francisco and São Francisco de Assis (1°44′22″S, 61°24′56″W). MZUSP 55847, 1 (200), Río Negro , 24.4 km below Paraná Aliaque (1°13′32″S 62°13′49″W). INPA 27493 1 (374); Rio Negro, Lago do Prato, Anavilhanas. USNM 375475, 1 (270); Rio Solimões (3°35′43″S, 61°07′16″W). MZUSP uncat.; 1 (197), Rio Solimões , below Purus (3°36′25″S, 61°19′40″W). MZUSP 56161, 2 (240–290), Rio Solimões , 15.4 km below Paraná do Taiacutuba (2°36′24′S 65°44′23″W). INPA 27490, 1 (362); INPA 17607, 1 (237); Rio Solimões , Ilha da Machantaria. INPA 17606, 1 (242); Rio Solimões. INPA 17604, 1 (308); Rio Purus , at Beruri. INPA 17605 2 (190–279); Rio Solimões , Costa do Marimba, Ilha do Careiro. Pará: FMNH 115515, 3 (188–236); Rio Amazonas between Paraná de Santa Rita and Rio Trombetas , between towns of Jurutí and Óbidos (1°56′7″S, 55°41′19″W). USNM 373027, 3 (186–286); Rio Trombetas , 9.9 km above Vila Aracuá (1°30′48″S, 56°10′19″W).

STERNARCHORHYNCHUS ROSENI MAGO- LECCIA

( FIGS 66–68 ; TABLE 12)

Sternarchorhynchus roseni (nomen nudum), Marrero & Taphorn, 1991: 129 [use of manuscript name; secondary sexual dimorphism in species discussed]. – Machado-Allison & Moreno, 1993: 88 [use of manuscript name; Venezuela, Guarico, Río Orituco ].

Sternarchorhynchus roseni Mago-Leccia, 1994: 99 , fig. 92 [type locality: Venezuela, Río Orinoco basin , Estado Apure, Río Apure in front of Jarina, near San Fernando de Apure]. – Taphorn et al., 1997: 80 [ Venezuela]. – Campos-da-Paz, 2000: 528 [recognized as valid species in key to species of Sternarchorhynchus ]. – Albert, 2003: 501 [in listing of members of Sternarchorhynchus ]. – Lasso et al., 2004b: 142 [ Río Orinoco basin in Colombia and Venezuela]. – Lasso et al., 2004a: 181 [ Venezuela; Río Orinoco basin ]. – Machado-Allison, 2006: 26 [ Venezuela]. – Crampton, 2007: 289 [widespread in Orinoco basin ; not cited occurrence in Amazon].

Diagnosis: Sternarchorhynchus roseni 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, having the scales along the mid-dorsal portion of the body anterior to the origin of the electroreceptive filament sparse and covered by skin, the presence of a more lightly coloured, narrow band of mid-dorsal pigmentation on the head and middorsal region of the body extending posteriorly to the origin of the electroreceptive filament and sometimes beyond that point, the possession of a total of eight to 11 teeth on the dentary, 16 precaudal vertebrae, 19–27 anterior unbranched anal-fin rays, 193–210 total anal-fin rays, the greatest body depth (8.6–10.9 of LEA), the caudal length (10.7–12.8 of LEA), the head depth at the nape (40.1–46.3 of HL), the head depth at the eye (23.0–29.9 of HL), the head width (19.7–23.0 of HL), the distance from the posterior naris to the snout (6.0–8.4 of HL), the distance from the posterior naris to the eye (49.8–63.4 of HL), the postocular distance (34.0–40.7 of HL), the pectoral-fin length (34.4–41.0 of HL), and the tail depth (11.0– 16.1 of caudal length).

Description: Morphometric data for holotype and paratypes in Table 12.

Lateral line extending to base of caudal fin, but absent on fin. Snout elongate, compressed and slightly curved ventrally, more so distally. Posterior naris located closer to tip of snout than to anterior margin of eye. Branchial opening restricted and situated slightly anterior to vertical through pectoral-fin origin. Location of anus and urogenital papilla apparently sexually dimorphic. Openings positioned within range between verticals running slightly anterior to slightly posterior to eye in smaller individuals, females, and mature males lacking expanded dentary and patch of enlarged dentition on dentary. Anus and urogenital aperture much more anteriorly positioned in males with definite patch of enlarged dentition on dentary and located between verticals approximately one-quarter to one-third distance between anterior limit of eye and tip of snout. Combined opening for anus and urogenital papilla slightly horizontally elongate in males with well-developed patch of teeth on dentary; opening more rounded in other examined specimens.

Premaxilla of small size, somewhat rounded, with seven to eight teeth (N = 2). Dentary with two rows of teeth with total of eight to 11 teeth (N = 2). Dentary form sexually dimorphic. Dentary in some males extending further anteriorly than in females and widened transversely into dorsally bulbous structure, rounded from dorsal view and bearing series of enlarged, slightly posteriorly recurved teeth. Mouth terminal with rictus located anterior to vertical through anterior naris in juveniles, posterior of that vertical in males with enlarged dentary with patch of teeth, but still located distinctly anterior of vertical through posterior naris.

Branchiostegal rays five; with first to third rays relatively narrow and elongate and fourth and fifth rays large and broad. Precaudal vertebrae 16 (12–13 anterior, three to four transitional; N = 10).

Pectoral-fin rays ii + 11–14 [ii + 12] (N = 25). Analfin origin located slightly posterior of vertical through anterior margin of opercle. Anterior unbranched analfin rays 19–27 (N = 18). Total anal-fin rays 193–210 [208] (N = 21); number of fin rays apparently increases ontogenetically based on correlation between greater body size and increased numbers of fin rays within examined samples. Scales above lateral line at midbody seven to 12 [12] (N = 25). Scales along mid-dorsal region of body somewhat sparse and not readily apparent on body surface. Origin of midsaggital electroreceptive filament located approximately at 62% of TL. Filament extending one to two scales posterior of vertical through Sexually dimorphic features for S. roseni are presented as two entries. First entry is data for all specimens other than sexually dimorphic mature males. Information for sexually dimorphic male in second entry based on two specimens of 385–405 mm total length. Number of specimens indicated in parentheses.

posterior terminus of base of anal fin. Tail compressed and of moderate length, ending in small and elongate caudal fin. Caudal-fin rays 12–16 [16] (N = 14).

Coloration in life: In his original description of S. roseni, Mago-Leccia (1994: 102) reported that recently collected males from the Río Apure, had a ‘dark, almost black’ life coloration with a dark snout and hyaline midsaggital electroreceptive filament (the thong of that author). Females collected together with the males were ‘gray with a snout clear which had a dark line contacting the midline pale stripe’ and the filament was reported as ‘grayish’ and the anal fin was reported to have a ‘dark border’.

Coloration in alcohol: Overall ground coloration light to dark brown. Head and body covered with relatively densely packed dark chromatophores. Size of individual chromatophores and intensity of pigmentation greater in overall darker specimens. Snout with variably distinct, narrow band of somewhat darker pigmentation extending forward from region anterior of orbit and reaching to anterior portion of snout in many specimens. Anterior portion of snout darker than adjoining areas in some males with welldeveloped patches of enlarged dentition on lower jaw. Dark band on lateral surface of snout apparent even in overall darkly pigmented specimens and forms lateral margin of narrow, lightly coloured, mid-dorsal band on snout. Lightly coloured mid-dorsal band on head expands laterally along dorsal portion of postocular region of head and continuous posteriorly with narrow, mid-dorsal lightly coloured stripe on body. Body pigmentation overall slightly darker dorsally, but with narrow, lightly coloured mid-dorsal stripe extending from rear of head posteriorly onto basal portions of electroreceptive filament and then to varying degrees further posteriorly in various specimens.

Pectoral-fin coloration ranging from nearly hyaline in many specimens to dusky in darker individuals, with dark chromatophores overlying pectoral-fin rays. Anal-fin pigmentation apparently sexually dimorphic. Anal fin completely hyaline in most examined specimens, including apparently mature females. Some of darker individuals with overall hyaline anal fins having basal portions of rays outlined by series of dark chromatophores and forming very faint band. Males with anteriorly and laterally expanded dentary with patch of enlarged dentary teeth have distal half of most of anal fin darker and forming distinct band; band extends across all rays in narrower posterior portion of fin. Caudal-fin pigmentation variable, with coloration of rays ranging from somewhat to distinctly dark and with pigmentation always more developed on basal portions of rays. Some males with expanded dentaries have additional distal dark pigmentation on caudal fin.

Distribution: Examined specimens of S. roseni all originated in the central portions of the Río Orinoco system in Colombia and Venezuela ( Fig. 68 ). Lasso et al. (2004b: 142) reported the species as inhabiting other portions of the basin ranging from the state of Delta Amacuro in eastern Venezuela to the Río Meta system in the western portions of the Río Orinoco system.

Ecology: Specimens of S. roseni collected at Caño Bravo in the Río Apure drainage of Venezuela came, in part, from a white water habitat over a substrate of sand and clay covered with leaf litter and at water depths of up to 1.5 m (de Santana et al., 2006: 279).

Secondary sexual dimorphism: Sternarchorhynchus roseni demonstrates sexual dimorphism of the anterior portion of the dentary and associated dentition comparable to that present in some congeners. The species also demonstrates a striking sexual dimorphism in the position of the anus and urogenital papilla. Females along with juveniles have the anus and urogenital papilla positioned approximately at the vertical through the eye. Mature males, as evidenced by the presence of a well-developed patch of enlarged teeth on the expanded anterior portion of the dentary, have the anus and urogenital papilla instead significantly shifted anteriorly and positioned in the region delimited by verticals running onequarter to one-third of distance from the anterior margin of the orbit to the tip of the snout.

Remarks: As aforementioned under Coloration in life, Mago-Leccia (1994) reported a distinct sexual dimorphism in the coloration in S. roseni , with males being much darker than females. Our samples demonstrate a significant degree of variation in overall coloration with the species. We found, however, that in preserved samples the mature males with well-developed patches of enlarged teeth on the expanded dentary had only a slightly darker coloration than did females collected at the same time. It is possible that the distinct sexual dimorphism in pigmentation reported by Mago-Leccia (1994) for S. roseni is apparent only in life or is limited to the breeding season.

Material examined

COLOMBIA. Río Meta, unspecified localities; IAVHP 2981, 1 (221), IAVHP 6278, 1 (129).

VENEZUELA. Apure: Río Apure, near of mouth of Río Manglar (approximately 7°52′N, 67°36′W); MCNG 50521, 1 (192). Río Apure, near San Fernando de Apure; INHS 28403, 1 (240); Río Apure (7°16.26′N, 71°5.20′W). AMNH 58665, 2 (233–253; paratypes), MBUCV 15809, 6 (212–273; paratypes), MBUCV 19839, 8 (144–256; paratypes). Río Apure, 1 km upstream from San Fernando de Apure; MBUCV 19843, 1 (400). Río Apure, 3 to 5 km downstream from bridge of San Fernando de Apure; MBUCV 19844, 1 (383). Río Apure, near Isla del Medio; MBUCV 20025, 2 (208–289; paratypes). Río Apure, between mouth of Río Portuguesa and San Fernando de Apure airport (7°54′00″N, 67°32′00″W); ANSP 165215, 2 (202–330). Río Apure, near San Fernando de Apure; MCNG 24068, 1 (216). Río Apure at confluence with Río Portuguesa; MBUCV 7562, 1 (143; paratype). Río Meta, upstream from confluence with Río Orinoco ; MBUCV 15722, 1 (171; paratype). MBUCV 15807, 5 (170–245; paratypes), MBUCV 15811, 1 (117; paratype); Río Apure, in front of Isla Apurito (8°00′N, 67°31′W). Río Apure, at Jarina (7°56′N, 67°30′W). MCNG 52591, 18 (115–172), Río Aruaca, Caño Bucaral ; MBUCV 20037, holotype (267), MBUCV 20066, 1 (166; paratype); MBUCV 15808, 2 (154–247; paratypes). Río Arauca, mouth of Caño Bucaral; MBUCV 15810, 1 (108; paratype). Río Apure, at La Rompia; MBUCV 15813, 1 (180; paratype). Río Apure, 10 km downstream of San Fernando de Apure (7°86′39″N, 67°39′17″W); MCNG 13875, 5 (161–285). Río Apure, mouth of Río Portuguesa near San Fernando de Apure (7°95′00″N, 67°52′78″W); MCNG 14040, 1 (206), MCNG 14041, 1 (145). Río Portuguesa, between Estudos Barinas and Guarico; MCNG 51457, 2 (175–323), MCNG 51458, 5 (172–240), MCNG 51459, 3 (166–222). Río Apure, Caño Caujarito; MCNG 45131, 2 (152–221). Río Apure, Caño Caicara, where crossed by bridge on road from Mantecal (7°22′N, 69°21′W); USNM 260248, 4 (164–222). Barinas: Río Apure, mouth of Río Portuguesa; MCNG 52552, 3 (185–335), MCNG 52546, 1 (326). Río Masparro , 5 km north-west from Libertad to Barinas; INHS 29916, 1 (255). Río Apure, Caño Bravo (8°00′00″N, 67°98′33″E); MCNG 49176, 1 (196), MCNG 49284, 1 (171), MCNG 49314, 3 (131–180), MCNG 49341, 1 (168), MCNG 49462, 1 (78), MCNG 49614, 1, (184), MCNG 51727, 1 (96), MCNG 51747, 4 (105–170), MCNG 51770, 1 (228), MCNG 51790, 2 (137–170), MCNG 52106, 1 (310), MCNG 52233, 8 (123–222), MCNG 52264, 1 (52). Bolivar: Río Orinoco , near Puerto Las Majadas, at confluence with Río Caura ; MBUCV 15697, 1 (217). Río Portuguesa (9°06′67″N, 69°50′00″W); MCNG 15827, 3 (91–120). Río Orinoco , near Isla de Farjado (8°22′N, 62°42W); USNM 228879, 1 (410). Delta de Amacuro : Río Orinoco, LACM 43252–3, 4 (186–377). Río Orinoco , old shipping channel south of Isla Portuguesa; MBUCV 10411, 1 (235; paratype). Río Orinoco , downstream from El Concejo; MBUCV 12201, 3 (228–260). Río Orinoco , at Isla Tres Caños (8°39′48″N, 61°58′40″W); USNM 228786, 1 (226). Guarico: Río Orituco ; MBUCV 5491, 1 (93; paratype). Río Orinoco , mouth of Caño Guine (8°39′54″N, 62°02′06″W); USNM 228880, 2 (333–413). Río Orituco (8°52′N, 67°18′W); USNM 260246, 1 (123). Río Guarico, at Flores Moradas ranch approximately 3–4 km east of road from Calabozo to San Fernando de Apure (8°27″N, 67°25″W); USNM 260249, 1 (242).

Figures

Figure 63. Map of central and northern South America showing geographical distribution of Sternarchorhynchus oxyrhynchus (1 – Essequibo River, reported type locality of species, but see Remarks in species account concerning possible erroneous locality information), and Sternarchorhynchus retzeri sp. nov. (2 = holotype locality) (some symbols represent more than one locality and/or lot of specimens).

Figure 64. Sternarchorhynchus retzeri sp. nov., holotype, sexually dimorphic male demonstrating modifications of dentary and dentary dentition, 297 mm total length, MCP 41636; Brazil, Amazonas, Rio Solimões, Rio Tefé, Tefé.

Figure 65. Sternarchorhynchus retzeri sp. nov., female, 382 mm total length, MCP 41635; Brazil, Amazonas, Rio Solimões.

Figure 66. Sternarchorhynchus roseni, sexually dimorphic male demonstrating modifications of dentary and dentary dentition, 383 mm total length, MBUCV 19844; Venezuela, Apure, Río Apure.

Figure 67. Sternarchorhynchus roseni, female, 377 mm total length, LACM 43252-3; Venezuela, Delta de Amacuro, Río Orinoco.

Figure 68. Map of central and northern South America showing geographical distribution of Sternarchorhynchus roseni, Sternarchorhynchus schwassmanni sp. nov. (1 = holotype locality), Sternarchorhynchus severii, and Sternarchorhynchus starksi sp. nov. (2 = holotype locality) (some symbols represent more than one locality and/or lot of specimens).