Tetragonopterus anostomus Silva & Benine, 2011

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: 27-29

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Tetragonopterus anostomus Silva & Benine, 2011


Tetragonopterus anostomus Silva & Benine, 2011 

Fig. 8View FIGURE 8

Tetragonopterus anostomus Silva & Benine, 2011: 50  –56 (original description; type locality: “Goiás state, Nova Crixás, rio Preto, rio Araguaia basin; Silva et al., 2013: 1613 –1631 (diagnosis); Araujo & Lucinda, 2014: 309 –315 (diagnosis). Tetragonopterus akamai Araujo & Lucinda, 2014: 309  –315. (original description; type locality: “Tocantins, Peixe, rio Tocantins close to the confluence with rio Santa Tereza).

Diagnosis. Tetragonopterus anostomus  is distinguished from all congeners by having subsuperior mouth (vs. terminal mouth). Tetragonopterus anostomus  differs from all other species, except T. araguaiensis  , by the presence of 17–19 gill rakers on the lower limb of the first gill arch (vs. 11–14). It differs from its congeners, except T. denticulatus  , T. juruena  and T. kuluene  by bearing 5–6 principal teeth on dentary (vs. 4) and by having thinner and sharper teeth on dentary (vs. large and more robust teeth). Tetragonopterus anostomus  further differs from T. ommatus  by the presence of 2–4 teeth on maxilla (vs. 7–8) and by having a mark centered on the caudal peduncle (vs. mark limited to the posterior portion of the peduncle). Tetragonopterus anostomus  differs from T. carvalhoi  by the presence of a rounded mark on the caudal peduncle (vs. a lozenge-shaped mark). It differs from T. rarus  by the absence of longitudinal dark stripes on the flank (vs. the presence of stripes). Tetragonopterus anostomus  differs from T. rarus  and T. georgiae  by having 3.5 longitudinal scale rows between lateral line and pelvic-fin origin (vs. 4.5–5.5). Finally, T. anostomus  differs from T. argenteus  by possessing eight predorsal scales (vs. 11–17).

Description. A detailed description of Tetragonopterus anostomus  was recently provided by Silva & Benine (2011).

Distribution. Tetragonopterus anostomus  was described from the rio Araguaia system. During the course of this study, several specimens of T. anostomus  were also found in the Rio Tocantins, which is not surprising given the fact that the rio Araguaia is a tributary of the rio Tocantins ( Fig. 2 a).

Remarks. Araujo & Lucinda (2014) recently described Tetragonopterus akamai  based on material collected in the Rio Tocantins basin. This species has a strong resemblance with T. anostomus  from the Tocantins-Araguaia system. A reanalysis of type specimens of T. akamai  provided evidence that T. akamai  is a junior synonym of T. anostomus  ( Fig. 9View FIGURE 9). The main character used to diagnose T. akamai  from T. anostomus  and from all others congeners is the shape of the anterodorsal portion of the maxilla, which is bent over and in close contact with the dorsal suface of the premaxilla (vs. anterodorsal portion of the maxilla not bent over and not in contact with the dorsal surface of the premaxilla, according to Araujo & Lucinda, 2014). The examination of a cleared and stained paratype ( UNTAbout UNT 2788) and non-type specimens ( MZUSPAbout MZUSP 52120) of T. akamai  revealed that the anterodorsal portion of the maxilla is not bent over the premaxilla as stated in the original description ( Araujo & Lucinda, 2014: fig. 2). The anterodorsal tip of the maxilla of a paratype of T. anostomus  (LBP 7687; Fig. 9View FIGURE 9 c) is even more bent downward than that observed in the paratype of T. akamai  ( UNTAbout UNT 2788; Fig. 9View FIGURE 9 a). Further, we noticed substantial variability in the shape of the anterodorsal portion of the maxilla in specimens of T. argenteus  . The summed evidence above clearly indicate that this character used to diagnose T. akamai  is extremely variable within Tetragonopterus  and should not be regarded as a valid character for diagnosing taxa at the specific level. Other proposed characters to diagnose T. akamai  from T. anostomus  are snout length and size of teeth in the inner series of premaxilla ( Araujo & Lucinda, 2014). However, we have not observed significant differences in these two features that allowed the distinction of two species. In order to further evaluate the hypothesis of conspecificity between these two nominal taxa, we included specimens of T. akamai  from a locality where paratypes of this nominal species were collected (Brejinho de Nazaré, Rio Tocantins; see Table 1) and used a molecular approach to evaluate the genetic divergence between both nominal taxa. Our results show no genetic divergence (genetic distance = 0.0%) between these samples ( Fig. 1View FIGURE 1), which means that T. akamai  from the Rio Tocantins has the same genetic information ( COIAbout COI sequences) as T. anostomus  from the Rio Araguaia. Thereby, both morphological and molecular evidence support that T. akamai  as a junior synonym of T. anostomus  .

Material examined. Types: Tetragonopterus anostomus  : MZUSPAbout MZUSP 108957View Materials, holotype, 45.4 mm SL, Goiás, Nova Crixás , Araguaia basin, Rio Preto , 14°22’18”S 50°39’13”W, L. S. Sousa, M. Melo, C. Chamon and L. M. Sousa, 26 Jul 2005GoogleMaps  . MZUSP 89295, 5 paratypes, 34.8–41.0 mm SL, collected with holotype. LBP 7687, 17 paratypes (2 c&s), 34.6–38.9 mm SL, Mato Grosso, Cocalinho, marginal lagoon of the Rio Araguaia. Tetragonopterus akamai  : UNTAbout UNT 2800, 2, 50.5– 49.9 mm SL, Tocantins, Peixe , Tocantins basin, Lagoa Água Branca , 11°49’20”S 48°38’40”W, 13 Oct 2000GoogleMaps  . UNTAbout UNT 5176, 5, 49.6–54.3 mm SL, Tocantins, Brejinho de Nazaré, Tocantins basin, Lagoa Capivara , 11°12’9”S 48°30’14”W, 14 Feb 1996GoogleMaps  . UNTAbout UNT 5175, 3, 34.1–35.6 mm SL, Tocantins, Ipueiras , Rio Tocantins basin, 11°18’55”S 48°27’28”W, L. Araujo & P. Lucinda, 28 Nov 2001GoogleMaps  . UNTAbout UNT 2788, 1 c&s, 54.4 mm SL, Tocantins, Brejinho de Nazaré, Tocantins basin, Lagoa Capivara , 11°12’9”S 48°30’14”W, L. Araujo & P. Lucinda, 14 Feb 1995GoogleMaps  . Non types. LBP 19055View Materials, 6, 36.9–42.8 mm SL, Tocantins, Brejinho de Nazaré, Tocantins basin, Rio Crixás , 11°03’14.3”S 48°34’22.0”WGoogleMaps  . MZUSPAbout MZUSP 18106, 1, 63.9 mm SL, Pará, Tocantins basin, Igarapé Muru  . MZUSPAbout MZUSP 52120, 18 (2 c&s), 44.2–55.8 mm SL, Tocantins, Araguaçu, Araguaia basin, Rio Água Fria , 12°44’42”S, 49°56’11”WGoogleMaps  . MZUSPAbout MZUSP 89096, 2, 44.3– 35.8 mm SL, Goiás, Aruanã, Araguaia basin, 14°45’50”S 050°57’50”WGoogleMaps  . MZUSPAbout MZUSP 89190, 1, 38.6 mm SL, Goiás, Aruanã, Araguaia basin, Rio do Peixe , 14°20’11”S 50°46’31”WGoogleMaps  . MZUSPAbout MZUSP 89446, 4, 30.3–41.1 mm SL, Goiás, Nova Crixás, Araguaia basin, 13°46’28”S 50°16’00”WGoogleMaps  . NUP 12746View Materials, 4, 47.6–52.6 mm SL, Mato Grosso, Cocalinho, Araguaia basin, Lago Montaria , 13°22’43”S 50°40’15”WGoogleMaps  . NUP 12922View Materials, 2, 61.7–62.4 mm SL, Goiás, São Miguel do Araguaia, Araguaia basin, Lago Piratinga , 13°04’10.5”S 50°35’06.7”W.GoogleMaps 


Universidad nacional de Tucumn


Museu de Zoologia da Universidade de Sao Paulo


University of Coimbra Botany Department














Tetragonopterus anostomus Silva & Benine, 2011

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


Tetragonopterus anostomus

Araujo 2014: 309Araujo 2014: 309
Silva 2013: 1613Silva 2011: 50