Tetragonopterus argenteus Cuvier 1816

Tetragonopterus argenteus Cuvier, 1816

(Fig. 3, Table 2)

Tetragonopterus argenteus Cuvier, 1816: 166 (description; type locality: “South America); Müller & Troschel, 1845: 1 –2, 13 (description; Brazil, Guyana); Günther,1864: 318 (description; Bahia?); Eigenmann, 1917: 54 –55 (description; from Orinoco and Guiana to the Paranahyba basin, Amazons and Paraguay, Paraná to Buenos Aires); Fowler, 1932: 352 (description; illustration; upper Paraguay, Descalvados, MT, Brazil); 1940: 90 (citation; Boca Chapare, Bolivia); 1941: 185 (citation; northeastern Brazil, Rio Paranaíba, Piau; Rio Jaguaribe, Cear); Géry, 1964a: 5 (citation; Peruvian Amazonia); Ringuelet et al., 1967: 131 –132 (description; upper Paran, Candelária and Arroio Uruguai, Missiones; Middle Paran, Empredado; Ilha Apipé Grande, Corrientes; Río La Plata; upper and middle río Paraguay; Goiás; Amazonas; Guyana); Ortega & Vari, 1986: 9 (citation: Amazonas, Peru); Stewart et al., 1987: 29 (citation, río Napo, Ecuador Oriental); Taphorn, 1992: 343 (description; Apure River drainage, illustration); Britski et al., 1999: 29 –31 (description; Pantanal matogrossense); Reis, 2003: 212 (list of Tetragonopterinae species); Lima et al., 2013; 352–353 (description; Rio Madeira basin, Brazil; photo).

Tetragonopterus sawa Castelnau, 1855: 65, pl. 33 (original description; type locality: “rio Crixas qui se jette dans L’Araguaia [Brazil]).

Tetragonopterus huberi Steindachner, 1909: 172 (original description; type locality: “Purus, Amazonas).

Diagnosis. Tetragonopteurs argenteus is distinguished from all other congeners by having 11–17 predorsal scales (vs. 7–9). It further differs from T. anostomus, T. denticulatus, T. kuluene, and T. juruena by having 4 principal teeth in dentary (vs. 5–6), and larger and more robust teeth (vs. thinner and sharper teeth; Silva et al. 2013: Fig. 2). Tetragonopterus argenteus differs from T. anostomus and T. araguaiensis by having 12–15 gill-rakers on the upper limb of the first gill arch (vs. 17–20; Silva et al. 2013: Fig. 3); it also differs from T. anostomus by having a terminal mouth (vs. subsuperior mouth). Tetragonopterus argenteus differs from T. ommatus sp. n. by bearing 1–4 maxillary teeth (vs. 7–8) and by the presence of a conspicuous dark mark on the caudal peduncle (vs. inconspicuous mark limited to the posterior portion of the caudal peduncle). Tetragonopterus argenteus differs from T. carvalhoi by the presence of a rounded dark mark on the caudal peduncle (vs. lozenge-shaped dark mark on the caudal peduncle). Tetragonopterus argenteus differs from T. rarus by the absence of dark longitudinal stripes on the trunk (vs. presence of such stripes); it differs from T. rarus and T. georgiae n. comb. by having 3.5 scale rows between lateral line and pelvic-fin origin (vs. 4.5–5.5). Finally, T. argenteus differs from T. denticulatus by having humeral marks separated by one or two vertical rows of scales (vs. humeral marks separated by three vertical scale rows).

Description. Morphometric data presented in Table 2. Body deep, compressed laterally, with greatest depth at dorsal-fin origin. Dorsal profile slightly convex between snout tip and vertical through middle of orbit; slightly concave from this point to end of occipital process; convex from that point to dorsal-fin origin. Slightly convex from dorsal-fin origin to adipose-fin end. Prepelvic region transversely flattened with distinct, longitudinally aligned lateral keels. Ventral profile of body convex from lower lip to anal-fin origin; straight or somewhat convex along base of anal fin. Caudal peduncle with dorsal and ventral profiles slightly concaves.

Olfactory lamellae 17 (1), 18 (4), 19 (7), 20 (5), 21 (7), 22 (16), 23 (8), 24 (6), 25 (4), 26 (7), 28 (2), 32 (1), 35 (2) or 40 (1). Snout length smaller than orbital diameter. Mouth terminal. Premaxilla in two rows of relatively robust teeth. Outer row with 4 (6), 5 (68), 6 (104), 7 (31) or 8 (10) teeth with three cusps, central cusps longest. Inner row with 4 (1), 5 (228) or 6 (3) teeth with three, four or five cusps; if present, central cusp twice as long and broader than other cusps. Maxilla with 1 (3), 2 (62), 3 (132) or 4 (29) teeth with three cusps. Dentary with 3 (1) or 4 (228) anteriormost teeth with three or five cusps followed by a smaller tricuspid tooth and 8–13 smaller conical teeth of similar size (5 c&s).

Dorsal-fin rays ii,9 (232). First unbranched ray very short. Dorsal-fin origin anterior to middle of body in SL. Anal-fin rays v,28 (1) v,29 (1), v,30 (4), v,31 (9), iv,32 (36), iv,33 (43), iv,34 (56), iv,35 (44), iv,36 (22), iv,37 (9) or iv,40 (1); posterior unbranched rays and anterior branched rays usually slightly longer than following rays. Analfin origin at vertical through base of last branched dorsal-fin ray. Pelvic-fin rays i,7 (228). Pelvic-fin origin anterior to vertical through dorsal-fin origin. Distal margin of pelvic fin reaching pelvic-fin origin with anterior rays longest. Tip of adpressed pelvic fin surpassing anal-fin origin. Pectoral-fin rays i,11 (4), i,12 (59), i,13 (105), i,14 (49) or i,15 (7). Caudal fin forked with i,17,i principal rays (5 c&s). Dorsal procurrent rays 11–13 (5 c&s) and ventral procurrent rays 8–9 (5 c&s).

Scales large and cycloid. Lateral line complete and distinctly curved downward anteriorly. Longitudinal scales 30 (5), 31 (17), 32 (48), 33 (79), 34 (52) or 35 (4). Scale rows between lateral line and dorsal-fin origin 7 (64) or 8 (162). Scale rows between lateral line and pelvic-fin origin 3.5 (234). Predorsal scales 11 (6), 12 (19), 13 (31), 14 (54), 15 (58), 16 (16), 17 (10) or 18 (2). Scale rows around caudal peduncle 13 (43) or 14 (138). Anal-fin base covered by a single row of small scales; anterior two thirds of lobes of caudal fin densely scaled in many specimens.

First gill arch with 8 (5), 9 (80), 10 (71) or 11 (13) gill rakers on upper limb and 12 (18), 13 (68), 14 (69) or 15 (6) gill rakers on lower limb. Total vertebrae 27, precaudal vertebrae 11, caudal vertebrae 16 (5 c&s). Supraneurals 3 (5 c&s).

Color in alcohol. General body color yellowish. Dorsal portion of head and body darkly pigmented (OS 18365 from Río Itaya in Peru with predorsal region densely pigmented). Dorsolateral portion of body with few minute chromatophores along distal margin of scales. Scales of ventrolateral portion of body unpigmented. Opercular and infraorbital bones silvery speckled with a few larger chromatophores. Two conspicuous vertical dark humeral marks separated by one or two vertical rows of scales. Anterior humeral mark extending over five horizontal scale rows above lateral line and two horizontal scale rows bellow lateral line. Posterior humeral mark extending over five or six horizontal scales rows above lateral line. Caudal peduncle with a rounded or vertically-oriented ellipsoid mark. Midlateral silvery stripe broad, extending from supracleithrum to anterior margin of the dark mark on the caudal peduncle. Anal, pelvic, and dorsal fins mostly hyaline, with chromatophores concentrated at distal portions of rays. Adipose fin speckled with small, dark chromatophores (Fig. 3 b).

Sexual dimorphism. Adult males with bony hooks on distal segments of fourth unbranched and anteriormost branched rays of anal fin; usually two bony hooks per segment. One adult male (ANSP 134765) from Río Meta in Colombia with bony hooks on fourth unbranched ray and on anteriormost 22 branched rays of anal fin.

Distribution. Tetragonopterus argenteus is distributed across the Amazon basin, upper Essequibo, Orinoco, Parnaíba, Jaguaribe, Paraguay and lower Paraná river basins (Fig. 2 a).

Material examined. Non types: Ecuador: ANSP 75902, 1, 102.3 mm SL, Chicherota, Napo basin, Río Pastaza, 2°25’15.1”S 76°38’39.4”W. ANSP 137656, 9, 42.7–97.8 mm SL, Río Lagartococha. Peru: ANSP 18365, 3, 75.1–82.7 mm SL, Loreto, Maynas, Río Itaya, 4°13’31.2”S 73°28’57.3”W. ANSP 143548, 1, 54.9 mm SL, Sandoval, Cosha, Río Madre de Diós. LBP 12401, 1, 65.6 mm SL, Loreto, San Juan Bautista, Río Marañon, 4°09’04.2”S 73°28’25.7”W. LBP 12578, 1, 57.7 mm SL, Loreto, Nauta, Río Marañon, 4°18’13.6”S 73°31’16.1”W. MZUSP 26393, 10, 40.8–67.5 mm SL, Pucallpa, Río Ucayali. MZUSP 26434, 4, 55.7–61.1 mm SL, Cocha, Supay. OS 18365, 3, 75.1–82.7 mm SL, Loreto, Maynas, Río Itaya, 4°13’31.2”S 73°28’57.3”W. Colombia: ANSP 131848, 4, 51.7–69.3 mm SL, Quebrada Venturosa, Río Meta. ANSP 134765, 3, 46.2–66.5 mm SL, Río Meta. ANSP 137585, 1, 54.9 mm SL, La Balsa, Río Meta, Río Negrito. ANSP 192316, 3, 45.0– 48.2 mm SL, Río Meta. LBP 18642, 2, 41.6–45.8 mm SL, Granada, Orinoco basin, Río Guaviare. Venezuela: LBP 3058, 2, 58.1–81.2 mm SL, Caicara de Orinoco, Río Orinoco, 7°38’11”N 66°19’04.2”W. LBP 3059, 1, 57.1 mm SL, Caicara del Orinoco, Río Orinoco, 7°38’11”N 66°19’04.2”W. Guyana: ANSP 190547, 6, 43.1–71.0 mm SL, Rupununi, Essequibo basin, Rupununi river. ANSP 193496, 3, 55–60 mm SL, Rupununi, Essequibo basin. Brazil: Acre: LBP 185, 2, 71.2–72.5 mm SL; LBP 16805, 8, 56.4–80.7 mm SL; LBP 16862, 1, 62.0 mm SL, Rio Acre-Purus, Rio Branco, 10°03.320’S 67°51.450’W. MZUSP 30363, 4, 41.7–47.4 mm SL, Tarauacá, Rio Juruá. MZUSP 50116, 2, 75.2–85.6 mm SL, Manuel Urbano, Rio Purus. MZUSP 50301, 3, 81.8–88.4 mm SL, Colocação Volta Grande, Rio Juruá. Amazonas: LIRP 4973, 1, 50.9 mm SL, Paraná do Janauacá. MZUSP 5773, 14, 66.3–88.4 mm SL, Paraná de Urucará. MZUSP 6516, 5, 64.9–80.6 mm SL, Manacapuru, Rio Solimões, 3°13’00”S 60°45’00”W. MZUSP 17353, 9, 41.7–66.4 mm SL, Coari, Rio Solimões, 3°55’00”S 63°20’00”W. MZUSP 17509, 9, 61.7–72.1 mm SL, Santo Antonio do Içá, Rio Içá, 3°08’00”S 67°57’00”. MZUSP 27756, 5, 70.9–82.5 mm SL, Benjamin Constant, Rio Içá mouth, 24°04’00”S 69°49’00”W. MZUSP 74668, 3, 64.8–67.0 mm SL, Rio Solimões, 3°22’00”S 60°11’00”W. MZUSP 74687, 9, 55.4–68.1 mm SL, Rio Solimões. Pará: LBP 17608, 1, 65.0 mm SL, Altamira, Rio Xingu, 3°30’14.3”S 52°02’19.9”W. MZUSP 3528, 3, 87.6–91.4 mm SL, Santarém, Rio Tapajós, 2°25’00”S 54°44’00”W. MZUSP 5449, 4, 65.1–79.4 mm SL, Oriximiná, Rio Trombetas, 1°46’00”S 55°52’00”W. MZUSP 9494, 6, 48.6–55.3 mm SL, Monte Alegre, 2°01’00”S 54°55’00”W. Piauí: ANSP 84415, 5, 53.1–61.9 mm SL, Terezina, Rio Parnaíba. MZUSP 5091, 15, 30.1–57.4 mm SL, Teresina, Rio Parnaíba, 5°05’00”S 42°50’00”W. MZUSP 74891, 14, 56.7–76.1 mm SL, Teresina, Rio Parnaíba. Ceará: ANSP 84416, 2, 72.5–82.1 mm SL, Russas, Rio Jaguaribe, Russas. Goiás: LBP 1832, 1, 68,8 mm SL, Aragarças, Rio Araguaia, 15°53’35.6”S 52o15’01”W. LBP 17275, 1, 60.9 mm SL, Britânia, Rio Araguaia, Rio Vermelho, 15°10’23.2”S 51°09’27.1”W. MZUSP 4814, 28, 42.6–58.5 mm SL, Aruanã, Rio Araguaia. MZUSP 54523, 1, 73.5 mm SL, Rio Araguaia. MZUSP 110039, 3, 76.4–88.2 mm SL, Minaçu, Rio Tocantins. Maranhão: LBP 5535, 1, 74.4 mm SL, Balsas, rio Parnaíba basin, Rio Balsas, 7°32’26”S 46°02’21”W. Mato Grosso: LBP 3967, 1, 59.4 mm SL, Cuiabá, Rio Paraguai, Rio Mutuca, 15°21’20”S 56°06’04”W. LBP 4633, 3, 64.5–72.3 mm SL, Poconé, Rio Paraguai. LBP 5108, 1, 67.6 mm SL, Cáceres, Rio Paraguay, 16°06’66”S 57°44’33”W. LBP 8442, 3, 51.8–63.8 mm SL, Cáceres, Rio Paraguai, 16°03’13.6”S 57°48’31.8”W. LBP 14046, 1, 79.5 mm SL, Poconé, Rio Paraguai, Rio Cuiabá, 17°50’49.9”S 57°26’22.3”W. LBP 15921, 1, 78,6 mm SL, Canarana, Rio Xingu, Rio Culuene, 13°31’02.8”S 53°04’41.8”W. LBP 15962, 3, 52.4– 44.3 mm SL, Canarana, Rio Culuene, 13°29’41.8”S 53°04’57.7”W. LIRP 713, 2, 65.4–65.9 mm SL, Barão de Melgaço, Rio Paraguai, Rio Cuiabá, 16°12’00”S 55°57’30”W. MZUSP 101060, 1, 52.1 mm SL, Rio Madeira basin, Rio Aripuanã, 10°12’33”S 59°27’39”W. MZUSP 101069, 15, 41.3–47.1 mm SL, Aripuanã, Rio Madeira basin, Rio Aripuanã. NUP 3381, 5, 62.9–82.0 mm SL, Aripuanã, Rio Madeira basin, Rio Aripuanã. NUP 4092, 3, 65.0– 87.6 mm SL, Chapada dos Guimarães, Rio Paraguai, Rio Cuiabá. NUP 7189, 2, 55.6–57.6 mm SL, Aripuanã. NUP 10758, 17, 21.9–44.4 mm SL, Rosário Oeste, Rio Paraguai basin, Rio Cuiabá. NUP 10768, 1, 101 mm SL, Nova Brasilândia, Rio Paraguay basin, Rio Manso. Mato Grosso do Sul: LBP 1476, 7, 27.4–42.4 mm SL, Coxim, Rio Paraguai, 18°25’42.5”S 54°50’02”W. LBP 1776, 4, 81.3–97.8 mm SL, Coxim, Rio Paraguai. LBP 3758, 20, 50.4–66.6 mm SL, Aquidauana, Rio Paraguai, 19°34’33.7”W 56°14’49.5”S. LBP 13558, 1, 51.5 mm SL, Corumbá, Rio Paraguai, 17°55’16”S 57°28’31.6”W. LBP 14036, 2, 55.7–94.1 mm SL, Poconé, Río Paraguai, 17°30’49”S 57°14’26.3”W. MZUSP 59706, 21, 45.1–60.8 mm SL, Aquidauana, Rio Paraguai basin, Rio Negro. Paraná: NUP 7341, 1, 110.9 mm SL, Foz do Iguaçu, Rio Paraná.