Moenkhausia rondoni, Mathubara & Toledo-Piza, 2020

Mathubara, Kleber & Toledo-Piza, Mônica, 2020, Taxonomic study of Moenkhausia cotinho Eigenmann, 1908 and Hemigrammus newboldi (Fernández-Yépez, 1949) with the description of two new species of Moenkhausia (Teleostei: Characiformes: Characidae), Zootaxa 4852 (1), pp. 1-40 : 18-25

Moenkhausia rondoni , new species

( Fig. 10 )

urn:lsid:zoobank.org:act:8C5EC3C9-08C3-416F-A923-75C152FB6DD1

Moenkhausia cotinho (not of Eigenmann): Pearson, 1924: 38 [listed; Bolivia: Río Beni]; Fowler, 1940:99 [listed: Bolivia, Río Beni]; Rojas & Rumiz, 2008: 79 [listed: Bolivia, Río Paraguá]; Pouilly et al., 2010: 81, table 2 [listed; Bolívia: Río Beni, Río Itenéz, Río Madre de Dios, Río Mamoré]; Pedroza et al., 2012: table 2, 12 [listed; Brazil: rio Guariba, rio Roosevelt]; Casatti et al., 2013: 1500 [listed; Brazil: rio Machado]; Lima et al., 2013: 308 [short description, photo, diagnosis in key, map of distribution; Brazil, middle rio Madeira]; Queiroz et al., 2013: 544 [listed; Brazil: Lago Cuniã]; Jegú et al., 2014: 127 [listed; Brazil and Bolivia: rio Guaporé and Río Itenez]; Sarmiento et al., 2016: 363 [listed; Bolivia: Río Beni];

Holotype: MZUSP 125775 (1, 38.4 mm SL). Brazil, Rondônia, Igarapé Arara, tributary of rio Madeira, Porto Velho , 10°0’48”S 65°19’5”W, F. Vieira, Aug 2015.

Paratypes: MZUSP 125776 (20, 29.1–37.5 mm SL); ZUEC 17236 (20, 33.1–37 mm SL); UFRO 6810 (16, 30.2–35.0 mm SL), same data as holotype .

Non-type material: Brazil: Amazonas: rio Madeira basin: INPA 26721 (3-6, 33.6–36.2 mm SL), Igarapé Inferno, rio Sucundurí, Apuí, 7°48’18”S 58°54’1”W, L. Rapp Py-Daniel, 1 Jul 2006; INPA 33688 (3-5, 33.8–41.8 mm SL), beach of rio Guariba - Resex Guariba, Apuí, 8°42’42”S 60°25’53”W, W. Pedroza, W. Ohara, F. Ribeiro, T. Teixeira, 6 Nov 2008; INPA 24699 (4-7, 38.6–44.6 mm SL), rio Mapuepauá, igarapé “Thayeria” Community Ponta Nova, Manaus, 5°22’4”S 60°44’52”W, L. Rapp Py-Daniel, 24 Sep 2004; INPA 262871 (1-1, 39.7 mm SL), rio Sucunduri, Community Terra Preta, Apuí, L. Rapp Py-Daniel, 27 Jun 2006; INPA 50572 (1-1, 15.5 mm SL), rio Canumã, Nova Olinda do Norte, 3°59’19”S 59°6’3”W, J. Zuanon, DA. Bastos, P. Guarido, J. Sodré and Eduardo, 6 Aug 2015; UFRO 22967 (5-10, 37.1 43.8 mm SL), rio Ipixuna, Humaitá, 7°21’8”S 63°14’57”W, F. Fernandes. Mato Grosso: rio Madeira basin: INPA 40988 (10-87, 35.6–55.1 mm SL), Aripuanã, Igarapé Praia Grande, downstream of Cachoeira Dardanelos, Aripuanã, Ichthyology team INPA, 9 Nov 1976; INPA 41050 (2-22, 32– 47.2 mm SL), rio Aripuanã, Igarapé do Poraquê, below Cachoeira de Dardanelos, Aripuanã, INPA Ichthyology team, 9 Nov 1976. MZUSP 99769 (1-1, 38.3 mm SL), rio Aripuanã, Balneário Primavera, downstream of Cachoeira de Dardanelos, Aripuanã, 10°9’54”S 59°26’55”W, F.A. Machado, C.M.C. Leite, N.E. Silva & F. Rosa, 12 Dec 2004; UFRO 12251 (8-125, 36.1–47.2 mm SL), rio Guaporé, under bridge of Vila Bela da Santíssima Trindade, Vila Bela da Santíssima Trindade, 15°0’27”S 59°57’22”W, W.M. Ohara; UFRO 12740 (1-1, 40.4 mm SL), rio Guaporé, under bridge of Vila Bela de Santíssima Trindade, Vila Bela da Santíssima Trindade, 15°0’27”S 59°57’22”W, W.M. Ohara; UFRO 21535 (1-1, 43.3 mm SL), rio Aripuanã, 32 km on road to Colniza, Aripuanã, 9°22’36”S 59°41’00”W, W.M. Ohara; UFRO 21842 (3-3, 44.2–48.7 mm SL), Igarapé Colniza, road Aripuanã, Aripuanã, 9°35’15”S 59°21’11”W, D.Hungria; UFRO 21861 (1-1, 42.1 mm SL), Igarapé Tigrinum, rio Branco,Aripuanã basins, 9°57’30”S 59°18’49”W, B. Barros; UFRO 22594 (5-7, 30.9–42.9 mm SL), Linha 32, road to Colniza, rio Branco, Aripuanã, 9°22’36”S 59°41’00”W, W.M. Ohara. UFRO 22630 (1-1, 40 mm SL), rio Aripuanã, Cachoeira das Andorinhas, Aripuanã, 10°9’58”S 59°27’0”W, WM. Ohara; ZUEC 9301 (2-3, 28– 34.9 mm SL), rio Aripuanã, Balneário Primavera, Aripuanã, 10°09’56”S 59°26’59”W, F.A. Machado et al., 3 Apr 2004; ZUEC 9691 (4-6, 26.6–30.2 mm SL), rio Aripuanã, downstream of Cachoeira de Dardanelos/Andorinhas, Aripuanã, 10°09’52”S 59°26’13”W, F.A. Machado et al., 8 Jul 2005. Rondônia: rio Madeira basin: INPA 12306 (2-8, 28.5–37.3 mm SL), rio Pimenta Bueno, Pimenta Bueno, G.M. dos Santos, 21 Nov 1984; INPA 12317 (2-4, 24.7–30.8 mm SL), rio Machado, Ji-Paraná, Ji-Paraná, G.M. dos Santos, 9 Nov 1983; INPA 2039 (2-2, 41.6–42 mm SL), rio Guaporé, 5 km above city, Costa Marques, 12°26’42”S 64°13’38”W, G.M. dos Santos; INPA 20845 (2-27, 24.8–35.1 mm SL), rio Machado, Nazaré, Ji-Paraná, Ji-Paraná, 10°53’7”S 61°57’6”W, G.M. dos Santos, 1 Oct 1985; INPA 20901 (1-2, 36.3 mm SL), rio Urupá, tributary of rio Machado, Ji-Paraná, G.M. dos Santos, 5 Jun 1984; INPA 20903 (4-10, 26.5–34.3 mm SL), rio Machado, 15 km below of Ji-Paraná, Ji-Paraná, 10°53’7”S 61°57’6”W, G.M. dos Santos, 9 Nov 1983; INPA 20913 (3-5, 36.5–43.2 mm SL), rio Guaporé, Pimenteiras, Costa Marques, 15°0’29”S 59°57’2”W, G.M. dos Santos, 1 Dec 1984; INPA 21618 (3-3, 37.6–40.7 mm SL), rio Guaporé, 5 km from Costa Marques, 12°26’42”S 64°13’38”W, G.M. dos Santos, 20 Nov 1983; INPA 21653 (2-4, 20.1–37.8 mm SL), rio Mamoré, ahead and just above Lago Guajará-Mirim, Guajará-Mirim, 10°47’59”S 65°23’24”W, G.M. dos Santos, 26 Nov 1983; MPEG 21878 (9-11, 27.4–42.3 mm SL), Reserva Biológica Jaru, Igarapé Lurdes, Ji-Paraná, 10°23’14”S 61°47’1”W, F. R. Silva. MPEG 21891 (2-2, 29.6–30.8 mm SL), REBIO Jaru, Igarapé Taboca, Ji-Paraná, 9°32’21”S 61°48’19”W, F. R. Silva; MPEG 21898 (1-1, 35.4 mm SL), REBIO Jaru, Igarapé Jacarezinho, Ji-Paraná, 10°18’25”S 61°49’28”W, FR. Silva; MPEG 21906 (1-1, 26.9 mm SL), Igarapé Jatuarana, Ji-Paraná, 10°20’43”S 61°48’48”W, FR. Silva; UFRO-I 326 (3-3, 21.7–38.5 mm SL), mouth of rio Mutumparaná, Porto Velho, 9°36’39”S 64°55’37”W, L.J. Queiroz. UFRO 716 (5- 9, 32.3–39.1 mm SL), Igarapé Arara, Porto Velho, 10°0’51”S 65°19’5”W, C. Röpke. UFRO-I 774 (1-1, 40 mm SL), mouth of rio Cautário, Porto Velho, 12°11’10”S 63°33’21”W, J.M. Monteiro-Netto, 18 Nov 2008; UFRO 1037 (3-3, 37.1–40.4 mm SL), rio Cautário, Costa Marques, 12°12’30”S 64°29’9”W, Equipe LIP/ UNIR; UFRO 1300 (5-15, 35.7–42.2 mm SL), Igarapé Arara, 10°0’51”S 65°19’5”W, ER. Silva; UFRO 1548 (4-10, 34.6–43 mm SL), rio Jaciparaná, tributary of rio Madeira, Jaciparaná, 9°17’1”S 64°23’57”W, CP. Röpke; UFRO 6027 (3-6, 39.8–41.9 mm SL), rio Guaporé, upstream of mouth of rio Corumbiara, Corumbiara, 13°18’3”S 62°1’37”W; UFRO 1770 (1-1, 37.1 mm SL), rio Guaporé, beach near mouth of rio Cautário, Pimenteiras do Oeste, D. Hungria. UFRO 1777 (1-1, 31.2 mm SL), upstream of rio Machado, Ji-Paraná, 8°20’32”S 62°41’31”W, A. Santos; UFRO 2182 (2-2, 42.3–46.1 mm SL), mouth of rio Mutumparaná, rio Madeira 9°37’0”S 64°56’4”W, R.A.S.B. Martins; UFRO 2296 (1-1, 32.2 mm SL), mouth of Igarapé Belmont, rio Madeira, Porto Velho, 8°38’34”S 63°50’56”W, J. Monteiro-Neto; UFRO 2392 (2-2, 20 - 36.3 mm SL), rio Guaporé, Pimenteiras do Oeste, Equipe LIP/ UNIR; UFRO 2472 (5-10, 26.7–48.1 mm SL), Igarapé Arara, Porto Velho, 10°0’52”S 65°17’55”W, J. Monteiro-Neto, 3 May 2009; UFRO 2933 (3-6, 33.4–40 mm SL), Lago Cuniã, rio Madeira, Porto Velho, 8°19’28”S 63°29’42”W, L. Queiroz; UFRO 3000 (3-3, 34.8–43.9 mm SL), mouth of rio Mutumparaná, Porto Velho, 9°36’39”S 64°55’37”W, A. Santos; UFRO 3060 (6-84, 28.9–40.1 mm SL), Igarapé Arara, tributary of right margin of rio Madeira, Porto Velho, 10°0’50”S 65°18’55”W, F. Vieira; UFRO 3576 (5-25, 23.6–39.2 mm SL), mouth of rio Jaciparaná, in front Lago Madalena, Jaciparaná, 9°17’19”S 64°24’35”W, A. Ribeiro. UFRO 3598 (2-2, 37.9–39.3 mm SL), upstream of igarapé Belmont, Porto Velho, 8°36’44”S 63°52’42”W, I. Nascimento; UFRO 3685 (1-1, 38.7 mm SL), Lago do Cuniã, rio Madeira, Porto Velho, 8°19’38”S 63°3’55”W, T.H.S. Pires; UFRO 3798 (1-1, 35.4 mm SL), mouth of rio Machado, rio Madeira, Porto Velho, 8°4’3”S 62°53’23”W, D. Dutra. UFRO 3800 (5-68, 31.6–40.1 mm SL), Lago do Cuniã, Porto Velho, 8°19’7”S 63°29’50”W, T.M. Silva; UFRO 3831 (5-59, 32.6–40 mm SL), Igarapé Arara, near Nova Mamoré, 10°0’51”S 65°19’9”W, Equipe LIP/ UNIR. UFRO 4154 (2-2, 30.4–43.2 mm SL), Três Praias, rio Jaciparaná, Porto Velho, 9°27’10”S 64°24’57”W, F. Vieira. UFRO 4259 (1-2, 18.60 mm SL), Lago do Cuniã, ICMBIO port, Porto Velho, 8°19’6”S 63°29’51”W, F. Vieira; UFRO 4443 (2-4, 36.2–40.2 mm SL), Ji-Paraná, 10°25’59”S 61°34’14”W, M. R. Anjos; UFRO 4575 (1-1, 37.7 mm SL), mouth of rio Jaciparaná, Lago Madalena, Porto Velho, 9°17’8”S 64°23’59”W, G.M. R. Guimarães; UFRO 4642 (4-8, 36– 42.5 mm SL), Lago Cuniã, rio Madeira, Porto Velho, 10°0’52”S 65°18’56”W, A. Santos; UFRO 4643 (6-46, 20.7–40.2 mm SL), Lago Cuniã, rio Madeira, Porto Velho, 8°19’2”S 63°20’1”W, E. Silva; UFRO 4790 (5-44, 38– 40.3 mm SL), rio Jaciparaná, 1200m in front old entrance of Lago Madalena, Jaciparaná, 9°17’17”S 64°24’35”W, A. Queiroz; UFRO 4852 (1-1, 35.80 mm SL), Colocação Jatobá, rio Cautário, Costa Marques, 12°35’00”S 60°55’00”W, G. Torrente-Vilara; UFRO-I 5076 (1-1, 41.7 mm SL), Lago Cuniã, rio Madeira, Porto Velho, 8°19’9”S 63°29’55”W, C. Lima; UFRO-I 5152 (1-1, 44.20 mm SL), rio Cautário, Porto Velho, 12°11’31”S 64°32’49”W, F. Fernandes; UFRO-I 5189 (2-2, 35.8–37.3 mm SL), rio Jaciparaná, near Lago Madalena, Porto Velho, 9°24’2”S 64°17’12”W, Equipe LIP/ UNIR, 1 Oct 2011; UFRO-I 5847 (2- 10, 14– 31.7 mm SL), in front of camp of Reserva Biológica Cuniã, São Carlos, 8°19’6”S 63°29’51”W, D.M. Ayalla, 15 Apr 2011; UFRO-I 5933 (1-1, 17.2 mm SL), rio Guaporé, beach near mouth of rio Cautário, Pimenteiras do Oeste, 12º12’50’’S 64º35’09’’W, D. Hungria, 10 Jan 2012; UFRO-I 6721 (5-65, 32.7–41.3 mm SL), Igarapé Arara, tributary of rio Madeira, Nova Mamoré, 10°0’50”S 65°18’55”W, J.A. Lima-Filho, 11 Jan 2012; UFRO-I 67595 (6- 38, 30.5–49 mm SL), Igarapé Arara, Porto Velho, 10°0’49”S 65°18’56”W, L.F. Machado-Neto; UFRO-I 6778, (1-1, 33.7 mm SL), rio Mutumparaná, Porto Velho, 9°37’2”S 64°56’1”W, Equipe LIP/ UNIR; UFRO-I 6779 (6-6, 26.8– 34.9 mm SL), Porto Velho, mouth of rio Mutumparaná, rio Madeira, 9°36’39”S 64°55’39”W, A. Santos; UFRO-I 6780 (2-3, 29.7–32.3 mm SL), Igarapé Arara, Nova Mamoré, 10°0’48”S 60°18’56”W, A.C. Mota; UFRO-I 678 (2- 3, 35.90–46.2 mm SL), mouth of rio Mutumparaná, rio Madeira, Porto Velho, 9°37’0”S 64°56’0”W, L.C. R. Melo; UFRO-I 6782 (4-4, 34.5–41.4 mm SL), rio Jaciparaná, beach in front of Lago Madalena, Porto Velho, 9°17’12”S 64°24’1”W, Equipe LIP/ UNIR; UFRO-I 6783 (7-20, 33.6–39.3 mm SL), Lago Cuniã, rio Madeira, Porto Velho, 8°19’37”S 63°30’27”W, D.M. Ayalla; UFRO-I 6784 (1-2, 42.3 mm SL), Três Praias, rio Jaciparaná, Porto Velho, 9°27’16”S 64°24’16”W, L.C. R. Melo; UFRO-I 6785 (4-12, 33– 41.1 mm SL), Igarapé Arara, Porto Velho, 10°0’47”S 65°18’52”W, A. Santos; UFRO-I 6786 (1-2, 28.7 mm SL), mouth of rio São Lourenço, Praia do Avião Porto Velho, 9°22’3”S 64°50’37”W, T. R. Araujo; UFRO-I 6787 (1-1, 33.6 mm SL), rio São Lourenço, near confluence of rio Madeira, Porto Velho, 9°22’5”S 64°50’44”W, T.H.S. Pires; UFRO-I 6788 (1-1, 25.9 mm SL), mouth of Igarapé Arara, rio Madeira, Porto Velho, 10°0’50”S 65°19’9”W, Equipe LIP/ UNIR; UFRO-I 6789 (1-2, 26.8 mm SL), mouth of rio Sotério, rio Mamoré, Guajará-Mirim, 11°35’55”S 65°13’48”W, C. Röpke; UFRO-I 6790 (1-2, 39 mm SL), rio Cautário, near Bico do Prancha, Costa Marques, 12°10’42”S 64°34’16”W, T. Fernandes; UFRO-I 6791 (1- 1, 36.4 mm SL), mouth of rio Jaciparaná, tributary of rio Madeira, Porto Velho, 9°13’2”S 64°22’58”W, T. Fernandes; UFRO-I 6792 (5-10, 25– 38.5 mm SL), mouth of igarapé Karipuna, rio Madeira, Porto Velho, 9°11’34”S 63°37’17”W, T.H.S. Pires; UFRO-I 6793 (1-1, 24.40 mm SL), Igarapé Arara, Nova Mamoré, 10°0’51”S 65°19’9”W, Equipe LIP/ UNIR; UFRO-I 6794 (1-1, 24.2 mm SL), Igarapé Karipuna, rio Madeira, Jaciparaná, 9°11’33”S 64°37’49”W, A.C. Mota; UFRO-I 7301 (2-6, 34.8–40.3 mm SL) rio Pacaás Novos, Guajará-Mirim, 10°52’58”S 65°15’24”W, J.A. Lima-Filho; UFRO-I 11277 (1-1, 43.9 mm SL), Igarapé, tributary of rio Machado, Rolim de Moura, 11°54’21”S 61°32’41”W, Equipe LIP/ UNIR; UFRO-I 1211 (2-4, 25.8–34.1 mm SL), rio Sotério, beach at mouth of rio Negro, Guajará-Mirim, 11°35’52”S 65°13’49”W, Equipe LIP/ UNIR; UFRO-I 13551 (1-1, 39.6 mm SL), beach at mouth of rio Pacaás Novos, Guajará-Mirim, 10°52’58”S 65°15’23”W, A. Ribeiro; UFRO-I 13649 (1- 1, 43.4 mm SL, rio Pacaás Novos, upstream of the mouth, Guajará-Mirim, 11°1’6”S 65°8’32”W, D. Hungria; UFRO-I 13657 (3-6, 35.2–41.1 mm SL), rio Guaporé, beach near mouth of rio Cautário, Pimenteiras do Oeste, 12°12’50”S 64°35’9”W, D. Hungria; UFRO-I 1579 (3-5, 36.6–38.8 mm SL), upstream of rio Jaciparaná, beach on left margin, Porto Velho, 9°27’16”S 64°24’52”W, T. Fernandes; UFRO-I 16763 (1-1, 25.1 mm SL), mouth of Igarapé Karipuna, rio Madeira, Porto Velho, 9°11’34”S 64°37’12”W, Equipe LIP/ UNIR; UFRO-I 17118 (4-6, 38.5– 42.8 mm SL), upstream of rio Jaciparaná, Lago das Três Praias, Porto Velho, 9°27’17”S 64°24’14”W, D. Hungria; UFRO-I 17376 (1-1, 41.7 mm SL), Igarapé Belmont, tributary of the right margin of rio Madeira, Porto Velho, J, Zuanon; UFRO-I 18129 (1-1, 37.7 mm SL), rio Cautário, Costa Marques, 12°11’52”S 64°32’48”W, I. Nascimento; UFRO-I 018307, (2-5, 41.4 - 43 mm SL), mouth of rio Jaciparaná, Lago Madalena, Jaciparaná, 9°17’12”S 64°24’1”W, A. Santos; UFRO-I 19638 (1-1, 35.7 mm SL), rio Guaporé, near Forte Príncipe da Beira, Pimenteiras do Oeste, J.G. Sodré; UFRO-I 20742 (1-1, 38.7 mm SL), rio Machado, REBIO Jaru, Ji-Paraná, 10°4’47”S 61°57’17”W, WM. Ohara; UFRO-I 21013 (5-12, 32.7–39.2 mm SL), rio Cautário, Costa Marques, 12°11’49”S 64°32’48”W, D. Hungria; UFRO-I 21444 (2-4, 33.3–34.8 mm SL), Fortaleza do Abunã, beach in front of district, Fortaleza do Abunã, 9°47’9”S 65°31’31”W, G. Vilara, 05 Nov 2009; UFRO-I 24012 (2-2, 36.5–38.6 mm SL), rio Guaporé, Pimenteiras do Oeste, 13°28’59”S 61°2’43”W, C. Zawadzki; UFRO-I 2625 (2-3, 36.1–42.6 mm SL), mouth of rio Jaciparaná, Jaciparaná, 9°17’11”S 64°23’58”W, A. Santos, 5 Oct 2009; UFRO-ICT 21974 (2-2, 28.6– 31.4 mm SL), rio Madeirinha, rio Machadinho, Vale do Anari, 9°15’38”S 61°21’33”W, B. Barros; Bolivia: Beni, Río Beni basin: INHS 37073 (10-10, 30.4–40.7 mm SL), Río Matos (Río Apere - Río Mamoré - rio Amazonas), 6 km to the Ecological station of Beni, on road to San Ignácio, LM. Page, BM. Burr, M.H. Sabaj, J. Sarmiento & A. S, Barrera, Jun 1995; Cochabamba, Río Beni basin: INHS 37283 (10-10, 27.7–37.4 mm SL), Río Chaparina (Río Yacuma - rio Amazonas Dr.) 11km W San Borja, L.M. Page, B.M. Burr, M.H. Sabaj, 8 Aug 1995; La Paz, Río Beni basin: FMNH 55037 (1-1, 39.20 mm SL), San Joaquin, J.D. Haseman, 6 Sep 1909. Peru: Madre de Dios, Río Madre de Dios basin: ANSP 185202 (2-2, 43.2–43.6 mm SL), Río Manuripe (Orton-Madre de Dios Dr.) road crossing at town of Mavila, 11°55’44”S 69°7’15”W, M. Sabaj, L. Sousa, M. Arce et al., 31 Jul 2004.

Diagnosis. Moenkhausia rondoni is distinguished from all congeners, except M. celibela , M. ceros , M. cosmops , M. cotinho , M. eurystaenia , M. lepidura , M. lineomaculata , M. mikia , M. monicae and M. pirahan , by the presence of five series of scales between the dorsal-fin origin and the lateral line and three series of scales between the lateral line and the pelvic-fin origin (vs. either more or fewer than five series of scales and three series of scales, respectively). It is distinguished from M. celibela , M. mikia , M. eurystaenia , and M. lepidura by lacking the dark pigmentation on the distal portion of at least one of the caudal-fin lobes (vs. present) and from M. monicae by the presence of a dark spot on the base of the caudal fin (vs. dark spot absent). Moenkhausia rondoni differs from M. cosmops , M. cotinho , M. lineomaculata , and M. pirahan , in the lack of a reticulate color pattern ( Fig. 4C ) (vs. reticulate color pattern present ( Fig. 4 A–B)). Although M. rondoni has the scales of the three dorsalmost longitudinal series of body with few chromatophores along the posterior margin, it does not form a reticulate color pattern. It further differs from those species in the relatively longer pectoral fin, its tip extending beyond the base of the innermost pelvic fin ray ( Fig. 5B ) (vs. tip of pectoral fin not extending beyond the base of innermost pelvic fin ray ( Fig. 5A )). Moenkhausia rondoni differs from M. ceros in having the black spot on the base of the caudal fin not reaching the posterior tip of the middle caudal-fin rays (vs. black spot on the base of the caudal fin reaching posterior tip of middle caudal-fin rays) and in the absence of hooks on the anal-fin rays of mature males (vs. presence of hooks on the anal-fin rays of mature males).

Description: Morphometric data presented in Table 2. Body compressed, moderately elongate. Largest specimen examined 57.5 mm SL; greatest body depth slightly anterior to dorsal-fin origin. Dorsal profile of head convex from snout tip to vertical through posterior nostril; straight to slightly convex from that point to tip of supraoccipital spine. Dorsal profile of body mostly convex to adipose fin; straight and posteriorly inclined along dorsal fin base; concave along dorsal margin of caudal peduncle. Ventral profile of head and body convex from anterior tip of dentary to anal-fin origin; straight to slightly convex along anal-fin base; concave along ventral margin of caudal peduncle. Mouth terminal, jaws equal. Posterior tip of maxilla at or slightly anterior to vertical through middle of orbit. Premaxillary teeth in two rows; outer row with 3(2), 4*(30), or 5(2) tricuspid teeth, inner row with 5*(35) tri- to pentacupid teeth. Maxilla without *(22), or with 2(15) teeth. Dentary with 4*(45) large pentacuspid teeth followed by a series of 6(3) diminutive tricuspid teeth ( Fig. 11 ). Central median cusp of all teeth longer than lateral cusps. Branchiostegal rays 4(3). First gill arch with 3(2) rakers on hypobranchial, 10(2) on ceratobranchial, 1(2) on intermediate cartilage, and 4(2) on epibranchial.

Supraneurals 4(33), obliquely oriented. First supraneural anterior to neural spine of fifth vertebra, fourth supraneural between neural spines of seventh and eighth vertebrae. Origin of dorsal fin at approximately half of SL, first pteryogiophore of dorsal fin anterior to neural spine of ninth vertebra. Dorsal-fin rays ii 9*(277), 10(3); supernumerary dorsal-fin rays 1(3). Origin of anal fin at approximately 2/3 of SL, first pterygiophore of anal fin anterior to haemal spine of 17 th vertebra. Anal fin falcate. Anal-fin rays iv, 16(4), 17*(31), 18(60), 19(67), 20(89), 21(23), 22(3). Pectoral-fin rays i, 11(24), 12(159), 13*(84), 14(6), tip of longest pectoral-fin ray extending beyond base of innermost pelvic fin ray. Pelvic-fin origin anterior to vertical through dorsal-fin origin. Pelvic-fin rays i*, 7*(277), tip of longest pelvic-fin ray reaching urogenital opening. Caudal fin forked, principal caudal-fin rays on dorsal lobe i, 9(2), and on ventral lobe i, 8(2), dorsal procurrent caudal-fin rays 10(2), ventral procurrent caudal-fin rays 10(2). Adipose fin anterior to vertical through base of posteriormost anal-fin ray.

Scales cycloid, with 5(5) well marked radii strongly radiating posteriorly from focus to posterior field of scale; circulii present only on lateral fields ( Fig. 7B ). Axillary scale on pectoral and pelvic fins. Proximal one third of caudal-fin lobes covered by small scales. Lateral line complete. Lateral-line tube present on caudal fin posterior to last perforated scale. Pored lateral-line scales 27(1), 28(1), 29(18), 30(65), 31*(85), 32(33), 33(1), 34(1). Longitudinal scales rows between dorsal-fin origin and lateral line 5*(267), longitudinal scale rows between lateral line and pelvic-fin origin 3*(266). Predorsal scales 8(1), 9(10), 10*(140), 11(29), 12(3). Middorsal scales between base of posteriormost dorsal-fin ray and adipose-fin 7(4), 8(180), 9(58). Circumpeduncular scales 12(23), 13*(98), 14(65). Total vertebrae 25(3): precaudal vertebrae 12(3) and caudal vertebrae 13(3).

Color in alcohol. Overall ground coloration of head and body yellowish to tan. Dorsal portion of head and body slightly darker than ventral. Infraorbitals 5 and 6 and opercular region with scattered chromatophores. Predorsal and preadipose scales dark, forming longitudinal line along dorsal midline of body. Scales of three dorsalmost longitudinal series of body with few chromatophores along posterior margin, but not resulting in reticulate pattern. Humeral blotch vertically elongate, with dorsal portion covering horizontally approximately two scales and extending vertically on scales of three longitudinal rows. Ventral portion of humeral blotch somewhat faded compared to dorsal. A longitudinal stripe extending from vertical through dorsal-fin origin to caudal peduncle; stripe silver on specimens that retain guanine on body, dark on other specimens. A dark rounded spot on base of middle caudal-fin rays, with pigmentation reaching to tip of middle caudal-fin rays in many specimens; dark pigmentation extending from caudal spot to base of dorsal and ventralmost principal caudal-fin rays. Caudal blotch preceded by light area on caudal peduncle. Caudal fin with light spot on each lobe, posterior to area of dark pigmentation. Dorsal, anal, adipose, pectoral and pelvic fins mostly hyaline with few scattered chromatophores ( Fig. 10 ).

Color in life. Based on a photograph of one specimen just after collection. Ground coloration of dorsolateral region of head and body yellowish to olive; ventrolateral region of head and body silvery. Dorsal region of eye yellowish. Dark pigmentation pattern of coloration in life similar to that described for preserved specimens except that humeral blotch is less marked than in preserved specimens due to presence of guanine on body and caudal spot is rounded. A silvery longitudinal stripe extending from vertical through dorsal-fin origin to caudal peduncle. Middle portion of caudal fin rays, proximal portion of dorsal-fin rays and adipose fin yellow; anterior anal-fin rays orange ( Lima et al. 2013: 308).

Distribution. Moenkhausia rondoni is widespread in the rio Madeira and its tributaries Río Beni and Río Madre de Dios. It is also reported for one locality in the rio Purus. It occurs in six of the regions proposed by Dagosta & de Pinna (2017) for the Amazon region (11. Mamoré, 12. Guaporé, 13. Beni-Madre de Dios, 14. Middle-Lower Madeira, 15. Madeira Shield Tributaries, 16. Purus) ( Fig. 12 ).

Etymology. The specific epithet, rondoni is in honor of Marshal Cândido Mariano da Silva Rondon, famous by having explored the Western portion of the Amazon basin. As an indigenist he gave support to the native populations of Brazil along all his life. Marshal Rondon gives name to the state of Rondônia, Brazil, where Moenkhausia rondoni is widely distributed.

Remarks. Lima et al. (2013:309) identified specimens of Moenkhausia from the rio Madeira basin as M. cotinho and described them as lacking a reticulate color pattern, a feature interpreted as characteristic of M. cotinho in previous studies ( Costa, 1994; Lima & Toledo-Piza 2001; but see comments below). As herein presented, M. cotinho has a reticulate color pattern and after examination of the specimens studied by Lima et al. (2013) and additional material from the same drainage, we concluded that they represent the species herein named as Moenkhausia rondoni . Although Moenkhausia cotinho occurs in a few localities in the rio Madeira basin, M. rondoni is much more widespread than M. cotinho within its area of distribution.

Pearson (1924), Fowler (1940), Pouilly et al. (2010) and Sarmiento et al. (2016) reported M. cotinho for drainages in Bolivia. We did not examine specimens listed by those authors, however specimens from Bolivia examined herein were identified as M. rondoni .

Figures

FIGURE 4. Detail of body at region ventral of dorsal fin of A) Moenkhausia cotinho, MNRJ 34892, 38.8 mm SL. B) M. pirahan, MZUSP 122063, 45.6 mm SL; C) M. rondoni, UFRO 3800, 40.1 mm SL and D) Hemigrammus newboldi, INHS 60312, 37.9 mm SL. Note the line of chromatophores forming a dark rim and delineating the posterior margin of the scales in A and B (reticulate pattern). 1: dark spot on posterior edge of scale, sometimes extending to anterior portion of adjacent scale; 2: light spot on central portion of scale.

FIGURE 5. Detail of body at region dorsal of pectoral and pelvic fins of A) Moenkhausia cotinho, MNRJ 34892, 38.8 mm SL; B) M. rondoni, MZUSP 125778, 33.1 mm SL. 1: vertical through tip of pectoral-fin rays; 2: vertical through base of innermost pelvic-fin ray.

FIGURE 7. Scales from region between dorsal-fin origin and lateral line of: A) Moenkhausia cotinho; B) M. rondoni; C) M. pirahan; D) Hemigrammus newboldi. Left side, lateral view. Scale bar = 1 mm.

FIGURE 10. Moenkhausia rondoni, holotype, MZUSP 125775, 38.4 mm SL. Brazil, Rondônia, Porto Velho, rio Madeira.

FIGURE 11. Premaxilla, maxilla and dentary of Moenkhausia rondoni, UFRO 12251, 43.1 mm SL. Right side, medial view. Scale bar = 1 mm.

FIGURE 12. Map of central and northern South America showing geographic distribution and type locality (red star) of Moenkhausia rondoni.