Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004 ), Zarske, Gery & Isbrucker, 2004

Silva, Gabriel S. C., Melo, Bruno F., Oliveira, Claudio & Benine, Ricardo C., 2016, Revision of the South American genus Tetragonopterus Cuvier, 1816 (Teleostei: Characidae) with description of four new species, Zootaxa 4200 (1), pp. 1-46 : 23-25

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Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004 )


Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004)

Fig. 6 View FIGURE 6 , Table 5 View TABLE 5

Moenkhausia rara Zarske, Géry & Isbrücker, 2004: 19 –30 (original description; type locality: “Surinam, Marowijne, rapid in Oelemari (Ulemari) River); Vari et al., 2009: 32 (listed, Guiana Shield).

Tetragonopterus lemniscatus Benine, Pelição & Vari, 2004: 339 –345 (original description; type locality: “Suriname, Nickerie District, tributary to Sisa Creek; Vari et al., 2009: 35 (listed, Guiana shield).

Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004) : Melo et al., 2011: 49 –56 (new combination); Melo et al., 2016: 709 –717 (molecular phylogeny).

Diagnosis. Tetragonopterus rarus is distinguished from all congeners by the presence of longitudinal dark stripes on the lateral surface of body ( Fig. 6 View FIGURE 6 ) (vs. absence of longitudinal dark stripes). In addition, T. rarus is distinguished from all congeners, except T. georgiae , by the number of longitudinal scale rows between lateral line and pelvic-fin origin (4.5–5.5 vs. 3.5). Tetragonopterus rarus differs from T. anostomus , T. denticulatus , T. juruena and T. kuluene by the presence of four principal dentary teeth (vs. 5–6) and by possessing relatively robust teeth on dentary (vs. sharper teeth). Tetragonopterus rarus differs from T. anostomus and T. araguaiensis by the presence of 12–13 gill-rakers on the lower limb of the first gill arch (vs. 16–20), and from T. carvalhoi by the presence of a rounded dark mark on the caudal peduncle (vs. lozengular dark mark on the caudal peduncle). Tetragonopterus rarus is further distinguished from T. ommatus by having 2–4 teeth on the maxilla (vs. 7–8) and by having the dark mark centered on caudal peduncle (vs. mark limited to the posterior portion of caudal peduncle); it differs from T. anostomus by having terminal mouth (vs. subsuperior mouth) and from T. anostomus and T. kuluene by having two humeral marks (vs. only one humeral mark). Tetragonopterus rarus differs from T. argenteus by the presence of 8 predorsal scales (vs. 11–17) and from T. denticulatus by having humeral marks separated by one vertical scale row (vs. marks separated by three vertical scale rows).

Description. Morphometric data summarized in Table 5 View TABLE 5 . Body shape compressed, moderately elongated when compared with congeners. Greatest body depth at dorsal-fin origin. Dorsal profile slightly convex between tip of snout and vertical through middle of orbit; slightly concave from this point to end of occipital process, convex from tip of occipital process to dorsal-fin origin; then slightly convex between dorsal-fin base and 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; slightly convex or straight along base of anal fin. Caudal peduncle with slightly concave dorsal and ventral profiles.

Mouth terminal. Upper and lower jaws of similar size. Premaxilla in two rows of relatively robust teeth. Outer row with 4 (3), 5 (7) or 6 (1) teeth with three cusps, central cusps longest. Inner row with 5 (11) teeth with three or five cusps, central cusps twice as long as the lateral cusps. Maxilla with 2 (2), 3 (6) or 4 (3) tricuspidate teeth. Dentary with 4 (5) or 5 (6) anteriormost teeth with 3 or 5 cusps, followed by one smaller teeth with three cusps and then several small conical teeth of similar size.

Dorsal-fin rays ii,9 (11). First unbranched ray shorter than second one. Dorsal-fin origin slightly anterior to middle of body. Anal-fin rays iv,28 (1), iv,30 (4), iv,31 (4) or iv,33 (2); posterior unbranched rays and anterior branched rays usually slightly longer than following rays. Anal-fin origin situated posterior to vertical line through posterior most branched dorsal-fin ray. Pelvic-fin rays i,7 (11); origin situated anterior to vertical line through dorsal-fin origin; tip of adpressed pelvic fin reaching one or two scales before first unbranched anal-fin ray. Pectoral-fin rays i,12 (1), i,13 (7) or i,14 (3). Caudal fin forked.

Scales large and cycloid. Lateral line complete and slightly bent downward anteriorly. Longitudinal scales 33 (5), 34 (3), or 35 (3). Scale rows between lateral line and dorsal-fin origin 6 (9) or 7 (2). Scale rows between lateral line and pelvic-fin origin 5 (10). Predorsal scales 7 to 9. Scale rows around caudal peduncle 14 (11). Anal-fin base covered by a single row of small scales. Lobes of caudal-fin base covered by small scales, smaller than those covering lateral surface of body.

First gill arch with 7 (2) or 8 (7) gill rakers on upper limb and 12 (3) or 13 (7) gill rakers on lower limb. Total vertebrae 30, precaudal vertebrae 11, intermediate vertebrae 2 and caudal vertebrae 17 (2 c&s). Supraneurals 3 (2 c&s).

Color in alcohol. General body color yellowish. Dorsal portions of head and body darkly pigmented. Dorsolateral portion of body with small chromatophores along distal margin of scales; scales of ventrolateral portion of body unpigmented. Opercular and infraorbital bones silvery. Posterior margin of scales densely pigmented resulting in dark, horizontally aligned stripes along the lateral surface of the body. Two conspicuous vertical dark humeral marks separated by one scale, with anterior mark more evident. Anterior humeral mark extending over four horizontal scale rows above and one horizontal scale rows bellow lateral line. Posterior humeral mark located over three horizontal scales rows above lateral line. Caudal peduncle with a rounded dark mark. Midlateral silvery stripe broad, extending from supracleithrum to caudal peduncle. Anal, pelvic, and dorsal fins hyaline, outlined by small chromatophores, more so in distal portions of the rays. Adipose fin mostly hyaline, scattered by small chromatophores at distal border ( Fig. 6 View FIGURE 6 a).

Sexual dimorphism. None observed.

Distribution. Tetragonopterus rarus is known from Corantijn River basin in western Suriname, the Marowijne River basin (type locality of Moenkhausia rara ), the Rio Jari, and Rio Paru of the Amazon basin, northern Brazil ( Fig. 2 a).

Remarks. The molecular phylogeny of Tetragonopterus ( Melo et al., 2016) supports the new combination proposed by Melo et al. (2011).

Material examined. Types: ANSP 94708, 1 paratype, 57.9 mm SL, Suriname /French Guyana, upper Marowijne, Tampoc (into Litany rivier), J. Géry, 29 Nov 1957 . ANSP 112246, 1 paratype, 33.7 mm SL, ANSP 139714, 2 paratypes, 35.9–48.4 mm SL, French Guyana, Marowijne basin, middle Mana River , between Saut-Chien and Saut-Topi-Topi, J. Géry , 15 Oct 1957. Non-types: Venezuela: ANSP 168083, 39 , 20.5–50.8 mm SL , Bolivar, Cuyuni basin, Rio Hacha. MZUSP 77808, 3 , 34.6–40.9 mm SL , Bolivar, Rio Nichare. Guyana: ANSP 177000 View Materials , not measured , Essequibo basin, Siparuni river , 4°44’41”N 59°00’18”W GoogleMaps . ANSP 190828, 16 , not measured, Rupununi region, upper Essequibo, Yukanopito falls . ANSP 190465, 4 , 35.3–41.5 mm SL, Rupununi region, Essequibo basin, Kuyuwini river . ANSP 190525, 7 , 31.2–56.2 mm SL, Rupununi region , Essequibo river, Kassi-Atae rapids . Suriname: ANSP 189638, 3 , 38.4–44.3 mm SL ; ANSP 189639, 3 , 38.4–44.3 mm SL; Marowijne basin , Sipaliwini, Anapaike, Lawa river . USNM 229604, 3 , 37–61.9 mm SL , Brokopondo , Marowijne river, 63 km Z. Van Afobaka. Brazil: LBP 21093 View Materials , 1, 26.4 mm SL , Amapá, Oiapoque, Rio Oyapock, Igarapé Pantanari , 3°48’47.6”N 51°48’31.6”W GoogleMaps . MZUSP 16758, 18 , 50.4–68.0 mm SL, Pará, Alto Paru d’Oeste, Amazon basin, upper Rio Paru .

TABLE 5. Morphometric data for Tetragonopterus rarus (n = 12). Range includes paratypes.

  Range Mean
Standard length (mm) 42.1–85.4 60.7
Percentages of standard length    
Greatest depth 46.0–52.6 49.4
Predorsal length 46.9–53.2 50.8
Prepectoral length 27.0–29.3 27.5
Prepelvic length 45.8–50.4 48.5
Preanal length 61.8–68.2 66.4
Caudal peduncle depth 8.3–11.8 10.3
Caudal peduncle length 6.3–9.4 8.5
Pectoral-fin length 22.2–23.9 23.3
Pelvic-fin length 14.6–24.2 18.7
Dorsal-fin length 32.6–42.2 33.2
Length of dorsal-fin base 14.7–17.6 16.7
Anal-fin length 16.8–25.4 17.6
Length of anal-fin base 34.2–38.7 37.6
Distance from eye to dorsal-fin origin 35.8–48.6 48.1
Distance from dorsal-fin origin to caudal-fin base 50.7–57.8 52.4
Head length 23.0–27.6 26.0
Head depth 21.2–27.6 22.0
Percentages of head length    
Snout length 22–24 23.3
Maxillary length 41–50 42.3
Horizontal orbital diameter 48–54 48.9
Least interorbital width 32–41 37.5

Academy of Natural Sciences of Philadelphia


Museu de Zoologia da Universidade de Sao Paulo


Smithsonian Institution, National Museum of Natural History














Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004 )

Silva, Gabriel S. C., Melo, Bruno F., Oliveira, Claudio & Benine, Ricardo C. 2016

Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004 )

Melo 2016: 709
Melo 2011: 49

Moenkhausia rara Zarske, Géry & Isbrücker, 2004 : 19

Vari 2009: 32
Zarske 2004: 19

Tetragonopterus lemniscatus Benine, Pelição & Vari, 2004 : 339

Vari 2009: 35
Benine 2004: 339
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