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

Tetragonopterus rarus ( Zarske, Géry & Isbrücker, 2004)

Fig. 6 , 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 ) (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 . 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 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 , not measured , Essequibo basin, Siparuni river , 4°44’41”N 59°00’18”W . 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, 1, 26.4 mm SL , Amapá, Oiapoque, Rio Oyapock, Igarapé Pantanari , 3°48’47.6”N 51°48’31.6”W . MZUSP 16758, 18 , 50.4–68.0 mm SL, Pará, Alto Paru d’Oeste, Amazon basin, upper Rio Paru .

Figures

FIGURE 6. Tetragonopterus rarus. a) MZUSP 88029, 85.4 mm SL, Brazil, Pará, Rio Paru, Amazon basin. Live specimens from (b) Marowijne and (c) Corantijn river basins, Suriname. Photos (b – c) by R. Covain.

Tables

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