Brachyhypopomus sullivani, Crampton & de Santana & Waddell & Lovejoy, 2016

Crampton, William G. R., Santana, Carlos D. de, Waddell, Joseph C. & Lovejoy, Nathan R., 2016, A taxonomic revision of the Neotropical electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes: Hypopomidae), with descriptions of 15 new species, Neotropical Ichthyology (e 150146) 14 (4), pp. 639-790 : 767-772

Brachyhypopomus sullivani , new species urn:lsid:zoobank.org:act:A5E0AE79-5691-4FEE-AA8B-F9BD8AE86D1C

( Figs. 1k , 43 ; Tables 2-5, 19)

Hypopomidae sp. 11. - Crampton, 1996a: 77, table 6.1.a, species list; 79, fig. 6.1 inset 36-37, color photographs; 85, fig. 6.2; 88, fig. 6.3; 92-94, figs. 6.4a, EOD data; 110, table 7.5, 113, table 7.7, 115, fig. 7.1, habitats ( Brazil, central Amazon, ecology and signal diversity).

Brachyhypopomus royeroi . - Sullivan, 1997: 126 (description in unpublished thesis with disclaimer stating that nomenclatural acts not available, a nomen nudum).

Brachyhypopomus sp. 6 . - Crampton, 1998a: 821, table 4 ( Brazil, Amazonas, species and EOD diversity). - Crampton, 1998b: 314, table 2, list of Brachyhypopomus ( Brazil, Amazonas, hypoxia tolerance).

Brachyhypopomus sp. F . - Crampton, 1999: 17 ( Brazil, Amazonas, Mamirauá Reserve, listing of species). - Crampton & Albert, 2006: 672, fig. 23.8, position in phylogenetic tree; 681, notes on EODs (gymnotiform species and EOD diversity). -Crampton et al., 2008: 231, fig. 6, black and white photograph of head of live individual ( Brazil, Amazonas, adaptations to hypoxia).

Brachyhypopomus beebei . - Galvis, 2006: 528, pl. 104c, color photograph of live individual ( Colombia, Amazonas, listing of Brachyhypopomus ).

Brachyhypopomus sp. “roy”. -Crampton, 2011: 176, table 10.2, species list; 179, figs. 10.2-10.3, phylogeny, geographical and ecological distributions (gymnotiform biology).- Tagliacollo et al., 2016: 28, fig. 5 (phylogeny of Gymnotiformes ).

Brachyhypopomus sp. 2 . -Crampton & Ribeiro, 2013: 240, color photograph ( Brazil, rio Madeira, listing of hypopomids).

Brachyhypopomus sp. “sullivani ”. - Crampton et al., 2016: 1-66, table 1, 3-4, figs. 1-7, 14-15, 18-20 (phylogeny, biogeography and ecology of Brachyhypopomus ).

Holotype. MUSM 39624, 108 mm TL, 91 mm LEA, Peru, Loreto. mun. Requena, stream nr. Jenaro Herrera, affl. río Ucayali, Amazonas dr., 04°54′39″S, 073°39′29″W, 21 Jul 2009, W. Crampton, E Correa Roldán, M. Aldea Guevara & J. Waddell.

Paratypes. 59 specimens. Peru. Loreto (localities are from Amazonas dr.; localities listed from nr. Jenaro Herrera are from the río Ucayali dr., mun. Requena; collected by W. Crampton, E. Correa Roldán, M. Aldea Guevara & J. Waddell unless stated otherwise). MUSM 44682 , 9 (6 immature, 72-94 mm, 2, female, 96-113 mm, 1 male, 107 mm), stream nr. Jenaro Herrera , 04°53′35″S, 073°39′01″W, 11-20 Jul 2009 . MUSM 44731 , 1 , immature, 110 mm, stream nr. Jenaro Herrera, 04°54′49″S, 073°39′43″W, 4 Aug 2009 . MZUSP 91427 , 2 , 45-87 mm, affl. quebrada Chica, nr. Jenaro Herrera , 04º55′S, 073º40′W, Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega & B. Crampton. UF 148513 , 1 , female, 112 mm, quebrada Chupiai nr. Jenaro Herrera , ca. 04°53′S, 073°39′W, 9 Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega & B. Crampton. UF 148515 , 2 (1 immature, 87 mm, 1 male, 94 mm), quebrada Salomé nr. Jenaro Herrera , 04º54′32″S, 073º35′37″W, 13 Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega & B. Crampton. UF 148516 , 9 , 98-120 mm, affl. quebrada Chica, nr. Jenaro Herrera , ca. 04º55′S, 073º40′W, 15 Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega & B. Crampton. UF 148517 , 5 (1 immature, 46 mm, 3 female, 88-105 mm, 1 male, 108 mm), affl. quebrada Chica, nr. Jenaro Herrera , 04º55′22″S, 073º39′45″W, 15 Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega & B. Crampton. UF 148518 , 5 , 95-104 mm, quebrada Chica, nr. Jenaro Herrera , ca. 04º55′S, 073º40′W, 15 Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega & B. Crampton. UF 148519 , 3 (1 immature, 103 mm, 1 female, 101 mm, 1 male, 125 mm), quebrada Fierro caño, affl. quebrada Sapuenillo, nr. Jenaro Herrera , 04º51′39″S, 073º38′59″W, 16 Jan 2004 , W. Crampton, R. Reis, F. Lima, H. Ortega, B. Crampton. UF 184008 , 6 (5 immature, 52- 118 mm, 1 female, 103 mm), stream near Jenaro Herrera , 04°52′42″S, 073°38′51″W, 12-16 Jul 2009 . USNM 405575 , 5 , immature, 58-70 mm, stream nr. Jenaro Herrera, 04°52′24″S, 073°38′49″W, 14 Jul 2009 . USNM 405576 , 3 (2 immature, 89-108 mm, 1 male, 101 mm), stream nr. Jenaro Herrera , 04°54′40″S, 073°39′29″W, 21 Jul 2009 . USNM 405577 , 8 (4 immature, 74-94 mm, 2 female, 101- 104 mm, 2 male, 114-123 mm), stream nr. Jenaro Herrera , 04°56′16″S, 073°39′20″W, 27 Jul 2009 .

Non-types. 326 specimens. Bolivia. Beni (localities from rio Madeira dr., Amazonas dr.). AMNH 39824, 4, 60-71 mm LEA, 10 km SE Costa Marques (Brazil), río Iténez floodplain (río Guaporé), affl. rio Mamoré , 12°30′37″S, 064°12′59″W . CBF 10253 , 1 , immature, 90 mm, mun. Riberalta, stream nr. lago San José, affl. río Beni, 10°54′47″S, 065°59′49″W . CBF 10254 , 1 , female, 127 mm , CBF 102455 , 1 , female, 122 mm , UMSS 7018 , 1 , immature, 66 mm, mun. Riberalta, stream nr. San José, nr. Riberalta, affl. río Beni, 10°55′32″S, 066°00′36″W . UF 177341 , 1 , female, 105 mm , UMSS 7019 , 1 , female, 136 mm, mun. Riberalta, Riberalta-Guayaramerín rd. , nr. km 43, affl. río Beni, 11°01′58″S, 065°44′53″W . Brazil (localities from Amazonas dr.). Acre. MCP 35527 , 1 , 85 mm, mun. rio Branco, igarapé Quinoa, affl. rio Acre, affl. rio Purus , ca. 10°03′S, 067°37′W . Amazonas. INPA 6611 , 1 , Santa Isabel do rio Negro , igarapé de Santo Antônio, nr. Nova Esperança, ca. 00°24′S, 065°01′W [coordinates for Santa Isabel do rio Negro ]. BMNH 1998.3.12.193, 1, female, 84 mm, BMNH 1998.3.12.210, 1, immature, 46 mm , INPA 9954 , 2 (1 immature, 78 mm, 1 female, 94 mm) , MCP 45288 , 1 , female, 92 mm, mun. Tefé, igarapé Curupira, at bridge of Estrada Agrovila rd., affl. lago Tefé ( rio Tefé ), 03º25′48″S, 064º44′15″W . BMNH 1998.3.12.208-209, 1, female, 91 mm, 1 male, 97 mm, MCP 45287 , 3 (2 immature, 60-84 mm, 1 female, 100 mm) , MCP 45336 , 16 (10 female, 81-100 mm, 6 male, 98-113 mm) , MCP 45464 , 1 , immature, 79 mm , MCP 45486 , 10 (2 immature, 84-85 mm, 3 female [1CS], 83-91 mm, 5 male [2CS], 91-101 mm) , MCP 45492 , 2 (1 female, 85 mm, 1 male, 99 mm) , UF 177357 , 2 , 86-88 mm, mun. Tefé, igarapé Repartimento, 1.5 km downstream from Estrada Agrovila rd., affl. lago Tefé ( rio Tefé ), 03º24′25″S, 064º44′08″W . INPA 8886 , 1 , rio Preto da Eva, downstream rio Preta da Eva , ca. 02°40′S, 059°40′W . MCP 41032 (part), 1, mun. Humaitá, stream on BR-319, ca. 96 km S Humaitá, affl. rio Pixuna [Ipixuna], affl. rio Purus , 08°05′31″S, 063°35′47″W . MCP 41033 (part), 1, 56 mm , MCP 41036 (part), 6, 43-85 mm, mun. Canutama, igarapé São João on hwy. BR-319, ca. 60 km S Humaitá, affl. rio Ipixuna, affl. rio Purus , 07°56′07″S, 063°20′03″W . MCP 41040 , 1 , 59 mm, mun. Humaitá, stream ca. 43 km E rio Madeira on Transamazon hwy., affl. rio Madeira , 07°38′49″S, 062°40′57″W . MCP 41042 (part), 2, 59-69 mm, mun. Humaitá, stream ca. 68 km E rio Madeira on Transamazon hwy., affl. rio Madeira , 07°44′02″S, 062°29′40″W . MCP 41045 (part), 1, 68 mm, mun. Humaitá, rio Maicimirim, ca. 45 km rio Madeira on Transamazon hwy., affl. rio Madeira , 07°38′04″S, 062°39′44″W . MCP 45310 , 5 (1 immature, 61 mm, 2 female, 65-67 mm, 2 male, 76-97 mm), mun. Maraã, lago Amanã, rio Baré, igarapé São Sebastião, rio Japurá , 02°17′05″S, 064°41′25″W . MCP 45325 , 1 , immature, 88 mm, mun. Alvarães, igarapé Jarauá, Nogueira-Alvarães rd., affl. Lago Tefé ( rio Tefé ), 03º15′06″S, 064º48′55″W . MCP 45434 , 1 , female, 76 mm, mun. Tefé, igarapé Xidarinini, affl. lago Tefé ( rio Tefé ), 03°22′46″S, 064°41′17″W . MCP 45449 , 1 , male, 109 mm, mun. Tefé, swamp, margin of igarapé Repartimento, at Estrada Agrovila rd., affl. lago Tefé ( rio Tefé ), 03º24′25″S, 064º44′08″W . MPEG 12450, 3, 79-85 mm, mun. Coari, stream in Urucu oil field, affl. rio Urucu , affl. lago de Coarí, Amazonas dr., 04°52′19″S , 065°15′02′W. MPEG 12458, 2, 73-82 mm, mun. Coari, igarapé Tartaruga, affl. rio Urucu , affl. lago de Coarí, affl. Amazonas dr., 04°53′55″S , 065°19′18′W. MPEG 12459, 2, 74-85 mm, MPEG 13110, 1, 62 mm, mun. Coari, igarapé Tamanduá, affl. rio Urucu , affl. lago de Coarí, 04°51′43″S , 065°15′54′W. MPEG 12504, 1, 74 mm, MPEG 12523, 4, 76-122 mm, mun. Coari, igarapé Lontra, affl. rio Urucu , affl. lago de Coarí, 04°52′47″S , 065°08′58′W. MCP 13670 , 1 , 96 mm, mun. Juriti, nr. Juriti, igarapé da Ponte, 02°10′47″S, 056°04′38″W . MZUSP 59227 , 1 , 41 mm, pools in beach, Tapera, rio Negro , ca. 00°12′S, 064°04′W . Mato Grosso. INPA 11585 , 2 , 103- 119 , INPA 11593 , 2 , 113-141 mm , INPA 11595 , 5 (3 CS), 85- 121 mm , INPA 11606 , 2 , 100-104 mm , INPA 11607 , 1 , 98 mm , INPA 11692 , 3 , 88-149 mm , INPA 11693 , 1 , 88 mm , INPA 11722 , 2 , 130- 130 mm, Igarapé doAeroporto, Humboldt [Aripuanã], rio Aripuanã, affl. rio Madeira , 10°11′18″S, 059°27′47″W . MPEG 1313, 1, 74 mm, mun. Juína, Reserva Ecológica Iquê, affl. rio Iquê, on AR 1, Vilhena-Juína hwy., affl. rio Juruena, affl. rio Tapajós , 11°25′S, 058°45′W [coordinates for Juína]. Pará. FMNH 70075, 13 (2 CS), 60- 112 mm, Missão do Cururu, rio Cururu , affl. rio Tapajós , 07°36′50″S, 057°38′58″W . MPEG 3039, 1, 87 mm, mun. igarapé-Açu, bridge over rio Cajueiro, affl. rio Marapanim , ca. 01°07′S, 047°36′W . MPEG 7177, 2, 68-77 mm, mun. Barcarena, igarapé Tauá, nr. hwy. PA 483, affl. Furo do Arrozal , affl. Baía de Marajó, ca. 01°34′S, 048°42′W . MPEG 7468, 1, 71 mm, MPEG 7471, 1, 73 mm, mun. Paragominas, igarapé Cachoeirinha, Fazenda Potiritá, affl. rio Potiritá, affl. rio Capim, affl. rio Guamá , affl. Baía de Marajó, 03°12′13″S , 047°39′52′W. MPEG 15623, 1, 103 mm, mun. Almeirim, rio Ipitinga, affl. rio Jari , 00°49′02″S, 053°56′27″W . UF 36599 , 1, 109 mm, igarapé Pirelli, affl. rio Maguari , affl. Baía de Marajó, 01°21′24″S, 048°19′36″W . Rondônia (localities from rio Madeira dr.). FMNH 54544, 1, 59 mm LEA, Maciel, rio Guaporé, affl. rio Mamoré , ca. 12°30′S, 062°20′W . MCP 41041 , 1 , 77 mm, mun. rio Crespo, stream ca. 20 km E hwy. BR- 364 in direction of rio Crespo, affl. rio Preto do Crespo , affl. rio Jamari , 09°42′21″S, 062°55′38″W . UFRO-I 6494, 2, 72-93 mm, stream, Estação Ecológica do Cuniã (ESEC) , 08°04′30″S, 063°28′34″W . UFRO-I 6495, 1, 73 mm, stream, ESEC, 08°04′07″S, 063°28′34″W. UFRO-I 6506, 4, 62-75 mm, UFRO-I 6508, 1, 67 mm, stream, ESEC, 08°05′30″S, 063°28′35″W. UFRO-I 6509, 1, 73 mm, stream, ESEC 08°04′09″S, 063°28′34″W. Roraima. INPA 7362 , 1 , INPA 7363 , 1 , INPA 7367 , 1 , igarapé do Cajú, 21 km Bonfim on old rd. to Normândia, rio Tacatú, affl. rio Branco, affl. rio Negro , ca. 03°32′N, 059°53′W . Colombia. Meta (localities from Orinoco dr.). MPEG 1105, 9, 90-122 mm, 7 km SE Puerto Lopez , affl. río Meta, ca. 04°03′N, 072°54′W . SU 50348 , 1 , 77 mm, nr. Los Micos, N end Cordillera Macarena, río Guaviare, río Meta, ca. 03°19′N, 073°54′W . SU 53762 , 1 , 67 mm LEA, stream affl. río Guayabero, ca. 5 mi. below El Refugio, affl. río Guayabero , affl. río Guaviare, ca. 02°17′N, 073°44′W . UF 19472 , 1 , 68 mm , UF 26012 , 3 , 66-67 mm , UF 33466 (part), 2, 83-89 mm , UF 33467 , 1 , 66 mm, 4.7 km W Puerto Gaitán, affl. río Yucao, affl. río Manacacias , affl. río Meta, ca. 04°18′N, 072°07′W . UF 33373 , 1, 102 mm, 47 km ENE Villavicencio, affl. río Humea , ca. 04°18′N, 073°11′W . UF 36603 , 2 , 93-98 mm, río Guatiguia nr. Villavicencio , affl. río Meta, ca. 04°09′N, 073°38′W . UF 80991 , 1 , 99 mm, small creek ca. 70 km E Villavicencio on rd. to Puerto López , ca. 04°03′N, 073°04′W . Ecuador. Sucumbios (localities from Río Napo dr.). FMNH 102278, 1, 121 mm, ca. 10 km N Marian and 1 km S río Cuyabeno below rd., affl. to río Cuyabeno, affl. río Aguarico , ca. 00°07′N, 076°17′W . FMNH 102283, 1, 103 mm, headwater río Aguas Negras, 1-2 km N Marian, affl. río Cuyabeno, affl. río Aguarico , ca. 00°46′S, 076°20′W . Guyana. Potaro-Siparuni (localities from Essequibo River dr.). ANSP 175954, 4, 57-70 mm, small creek crossing Kurupukari-Surama River rd. ca. 2.0 mi. from Kurupukari [Iwokroma] field station, 04°30′12″N, 058°42′32″W . FMNH 53323, 1, 99 mm, Chipoo Creek, affl. Ireng River , ca. 04°42′N, 059°06′W . ROM 62556, 1, 83 mm, stream affl. Siparuni River, affl. Siparuni River , 04°49′11″N, 058°51′01″W . Peru. Loreto. ANSP 178620, 4, 50-123 mm, caño Sabolito, terra firme stream, ca. 25 mi. S Iquitos, affl. río Amazonas , 04°14′45″S, 073°24′57″W . INHS 43903, 3, 64-79 mm, quebrada Shushuna, on rd. to Corrientillos, affl. rio Nanay , 03°49′48″S, 073°20′14″W . MUSM 5402 , 2 , 113-126 mm, stream nr. Jenaro Herrera, affl. río Ucayali, ca. 04°54′S, 073°37′W . MUSM 14494 (part), 1, 131 mm, Lagartococha, Aguas Negras, río Aguarico, affl. río Napo , 00°31′22″S, 075°15′25″W . MUSM 44695 , 40 (25 immature, 62-113 mm, 13 female, 76-112 mm, 2 male, 84-112 mm), stream nr. Jenaro Herrera, 04°51′51″S, 073°38′45″W . MUSM 44752 , 4 (3 immature, 17-85 mm, 1 female, 104 mm), stream nr. Jenaro Herrera, affl. río Ucayali, 04°54′54″S, 073°39′25″W . MUSM 44763 , 1 , immature, 55 mm, stream nr. Jenaro Herrera, affl. río Ucayali, 04°54′36″S, 073°39′58″W . UF 148514 , 7 (1 immature, 92 mm, 3 female, 98-107 mm, 3 male, 103-125 mm), Quebreda Sapuena, nr. Jenaro Herrera, 04°54′49″S, 073°34′59″W . UF 183772 , 4 , 29-79 mm, río Nanay , 03°53′50″S, 073°40′01″W . UF 184012 , 10 (8 immature, 66- 118 mm, 1 female, 98 mm, 1 male, 104 mm), stream nr. Jenaro Herrera, 04°53′59″S, 073°38′51″W . UF 184019 , 11 (8 immature, 62-89 mm, 2 female, 108-110 mm, 1 male, 102 mm), stream nr. Jenaro Herrera, 04°55′19″S, 073°38′57″W . UF 184024 , 21 (11 immature, 56-114 mm, 6 female, 90-109 mm, 3 male, 113-116 mm), stream nr. Jenaro Herrera, 04°54′15″S, 073°36′53″W . Venezuela. Amazonas. AMNH 230873, 1, 85 mm , MBUCV-V 29177 , 1 , 86 mm, 1 hr. downstream Campamento Yutaje, río Coracora, affl. río Manapiari, affl. río Ventuari , Orinoco dr., 05°36′25″N, 066°07′03″W . MBUCV-V 228 (part), 2, 84-106 mm, Caños Parú and Canna, upper río Ventuari , Orinoco dr., no coordinates . MBUCV-V 3460 , 3 , 78-83 mm, caño Iguapo, E La Esmeralda, ca. 03°10′N, 065°33′W . MBUCV-V 12986 , 1, 143 mm, Tobogan de la Selva, ca. 36 km de Puerto Ayacucho, affl. río Orinoco , Orinoco dr., 05°23′13″N, 067°37′02″W . MBUCV-V 14330 , 1, 131 mm, small stream nr. Sarama Sota, upper río Cataniapo , Orinoco dr., 05°38′00″N, 067°07′40″W . MBUCV-V 14678 , 1, 132 mm, 0.5- 1 km upstream La Neblina basecamp, río Baria, affl. río Casiquiare, affl. rio Negro , Amazonas dr., ca. 00°50′N, 066°05′W . MBUCV-V 14713 , 5 (2 measured, 120-122 mm), stream nr. La Neblina basecamp, río Baria, affl. río Casiquiare , affl. rio Negro , Amazonas dr., ca. 00°50′N, 066°05′W . MBUCV-V 14720 , 1 , male, 152 mm, La Neblina basecamp, río Baria, aff río Casiquiare , affl. rio Negro , Amazonas dr., ca. 00°50′N, 066°05′W . MBUCV-V 14760 , 1 , 82 mm, stream, 100 m before intersection of Gavilán and Las Palmas, affl. río Cataniapo , Orinoco dr., 05°32′45″N, 67°23′36″W . MBUCV-V 14768 , 1 , 78 mm, Raudal Yahui, 5 km upstream La Reforma, río Cataniapo, affl. río Orinoco , Orinoco dr., ca. 05°33′N, 067°31′W . UF 177354 , 11 (8 immature, 73-104 mm, 4 female, 73-127 mm, 2 male, 89-117 mm, on rd. from Puerto Ayacucho to Gavilan , caño Culebra , affl. río Cataniapo , Orinoco dr., 05°32′48″N, 067°26′55″W. UF 177355 , 6 , 60-117 mm (3 CS), on rd. from Puerto Ayacucho to Gavilan, caño Moia, affl. río Cataniapo , Orinoco dr., 05°32′26″N, 067°23′02″W. UF 177356 , 8 , 61-83 mm, rd. from Puerto Ayacucho to Gavilan, caño Samaria, affl. rio Cataniapo , Orinoco dr., 05°33′52″N, 067°28′15″W. USNM 266718 , 3 , 80-119 mm, “ Cãno Igapo ” [probably río Iguapo ], E La Esmeraldas [ La Esmeralda], affl. upper río Orinoco , Orinoco dr., ca. 03°07′N, 065°28′W. Apure. MCNG 26553, 2, 62-63 mm LEA, stream W Parque Nacional Galeras del Cinaruco, affl. río Cinaruco , Orinoco dr., ca. 06°34′N, 067°17′W. Bolívar. SU 54492 , 1 , 73 mm LEA, SU 54612 , 1 , 65 mm LEA, mun. Caicara del Orinoco , caño de Quiribana, Orinoco dr., ca. 07°32′N, 066°08′W.

Diagnosis. Brachyhypopomus sullivani is diagnosed from congeners by the following combination of characters:

precaudal vertebrae 15-18, vs. 19-26 in B. alberti , B. arrayae , B. beebei , B. belindae , B. draco , B. hamiltoni , B. janeiroensis , B. jureiae , B. palenque , and B. verdii ; anal-fin rays 143-185, vs. 190-293 in B. bennetti , B. brevirostris , B. bullocki , B. diazi , B. hendersoni , B. occidentalis , and B. walteri ; scales present in middorsal region, vs. absent in B. benjamini and B. provenzanoi ; accessory electric organ over the opercular region absent, vs. present in B. bombilla , B. menezesi , and B. regani ; head depth at eye 38.5-47.6% HL, vs. 47.8-59.9% in B. cunia , B. gauderio , and B. pinnicaudatus ; presence of scattered conspicuous black or charcoal flecks on flank, vs. absence in B. batesi and B. flavipomus .

Description. Head and body shape, and pigmentation illustrated in Figs. 1k and 43 . Meristic and morphometric data for examined specimens presented in Tables 2-5 and 19. Body shallow to moderate in depth. Head short to moderate in length and shallow to moderate in depth. Dorsal profile of head approximately straight from occiput to snout, ventral profile of head approximately straight between operculum and snout, snout rounded. Eye small to moderate in size. Upper jaw with moderate sigmoidal angle between premaxillary and maxillary portions in lateral view. Accessory electric organ (AEO) over operculum absent. Gill filaments on first gill arch 29-33 (median 31, n = 6). Pectoral fin of moderate width, pectoral-fin rays 11-16 (median of 11 in populations from the upper Amazon of Peru; mode of 14 in populations from upper rio Madeira, and from río Orinoco). Precaudal vertebrae 15-17 (mode of 16 in all populations), including 1-2 transitional vertebrae. Anal-fin origin slightly (<0.25 HL distance) posterior to, or near, tip of pectoral fin. Anal-fin rays 143-184 (median of 171 in populations from the upper Amazon of Peru; 159 from the upper rio Madeira; and 171 from the río Orinoco). Dorsal rami of recurrent branch of anterior lateral line nerve not visible. Middorsal region of body scaled. Rows of scales above lateral line 5-7 (mode 6). Lateral line continuous. Extensive network of epidermal canals dorsal to lateral line in posterior half of body, extending to about midway from lateral line to dorsal midline and forming a crisscrossing pattern of posteriorly converging chevrons. Groove-like canals are depigmented or almost depigmented, sometimes with chromatophores along margins, and are filled with a translucent material covered with skin (overlain by scales). Groove-like canals with apparent partitioning into rectangular segments and with pores to exterior located at posterior ends in many cases (possibly tuberous electroreceptors). Three bilateral horizontal columns of electrocytes at anal-fin terminus and at mid-point between anal-fin terminus and tip of caudal filament in immature, mature female, and mature male specimens. Caudal filament short to moderate in length.

Coloration. ( Figs. 1k , 43 ). Background pale tan to dark brown. Dorsal region without prominent depigmented pale stripe extending along midline from occipital region to base of caudal filament, although in some individuals there is an indistinct lighter middorsal stripe in posterior third to half of body. Dorsal region variably pigmented, often with irregular dark blotches against a homogenous lighter background, sometimes with dark blotches forming a single intermittent series along dorsal midline. Dark blotches restricted to dorsal region, never extending far ventrally and only just visible in lateral view. No vertical stripes or lines on flank; flank with evenly scattered chromatophores, darker dorsally and lighter ventrally, especially over pterygiophores. Characteristic prominent dark brown or black flecks scattered irregularly over flank. Caudal filament darker than body, with some irregular dark markings. Head with evenly scattered dark chromatophores, darker dorsally. Eye with indistinct to very distinct suborbital patch or stripe of chromatophores and subcutaneous pigmentation. Pectoral and anal-fin membranes and rays hyaline. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills.

Size. A Brachyhypopomus of small adult size, largest specimen examined 152 mm TL, 123 mm LEA (n = 390). Largest male specimen examined 152 mm TL, 123 mm LEA (n = 36). Largest female specimen examined 127 mm TL, 100 mm LEA (n = 67).

Sexual dimorphism. No known secondary sexual dimorphism.

Geographic distribution. Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela ( Fig. 44 ). Widely distributed through the Amazon basin including multiple sites in the upper, central, and lower Amazon, the Negro, Purus, lower and upper Madeira, and Tapajós drainages. Known from some coastal drainages in Pará state, near the mouth of the rio Tocantins. Known also from parts of the Orinoco basin, and from the Essequibo River.

Population variation: We found overlap in the range of meristic counts ( Tables 2-5) and morphometric measurements ( Table 19), and observed similar pigmentation among populations of B. sullivani across its entire distribution. One meristic character, the number of pectoral-fin rays, is somewhat divergent between populations in the upper Amazon (11-13, mode 11) vs. the upper Madeira (13-14, mode 14) and Orinoco (13-15, mode 14). These observations, in combination with molecular data ( Crampton et al., 2016), support the hypothesis that all populations we have assigned to B. sullivani are members of a single geographically widespread species, which is morphologically and genetically distinct from all congeners.

Ecological notes. Brachyhypopomus sullivani is restricted to gently flowing, normoxic, low-conductivity streams and small rivers in closed canopy rainforest and savanna, where it is typically encountered in or near aquatic vegetation, root mass, or leaf litter. See description of B. benjamini for water quality parameters of the area of the type locality. Crampton et al. (2008) documented the relatively small gill sizes of B. sullivani relative to congeners that occur in seasonally hypoxic whitewater floodplain systems. Breeding occurs during the rainy season; both in the type locality, and in the vicinity of Tefé, Brazil (approximately December to April in both regions) (JCW, WGRC unpublished data). Stomach contents of specimens from the type locality comprise aquatic insect larvae (primarily Chironomidae ), and other small aquatic invertebrates (JCW, WGRC unpublished data).

Co-occurring congeners: In the upper, central, and lower Amazon (including lower Madeira, but excluding upper Madeira), B. sullivani occurs in sympatry and ecological syntopy with B. batesi , B. beebei , B. benjamini , B. brevirostris , B. verdii , and B. walteri , and exhibits an allotopic distribution to B. belindae , B. bennetti , B. cunia , B. flavipomus , B. hamiltoni , B. hendersoni , B. pinnicaudatus , and B. regani (note: in the lower Amazon populations of B. regani occur in low-conductivity systems in syntopy with B. sullivani ). In the upper Madeira, B. sullivani is known to occur in sympatry with B. alberti , B. brevirostris , and B. walteri , and in allotopy with B. arrayae , B. bombilla , and B. cunia . In the rio Negro B. sullivani occurs in sympatry with B. batesi , B. beebei , B. brevirostris , B. bullocki , B. hendersoni , B. regani , and B. walteri (likely in syntopy with all these species except B. hendersoni , which is a floodplain species). In the río Orinoco B. sullivani occurs in sympatry and syntopy with B. beebei , B. brevirostris , B. bullocki , B. diazi , B. provenzanoi , and B. regani (likely in syntopy with all these species except B. diazi which is restricted to high-conductivity systems). In the Essequibo River, B. sullivani occurs in sympatry with B. beebei , B. brevirostris , B. bullocki , B. hendersoni , B. regani , and B. walteri (likely in syntopy with all these species except B. hendersoni , which is a floodplain endemic).

Etymology. The specific name is a patronym (noun in the genitive case) in honor of John P. Sullivan, American ( USA) ichthyologist, for his contributions to gymnotiform biology.

Local names. Bolivia: cuchillo; Brazil: sarapó; Colombia: cuchillo; Ecuador: cuchillo, yayo; Guyana: knife fish; Peru: macana; Venezuela: cuchillo.

Figures

Fig. 1. Live individuals of 12 sympatric species of Brachyhypopomus and one species of Microsternarchus from the vicinity of Tefé, Amazonas, Brazil (Amazonas dr.). a. Brachyhypopomus batesi MCP 45312 (WC01.191293b), immature, 102 mm TL. b. Brachyhypopomus beebei head – uncat., immature, 75 mm TL; body – MCP 45450 (WC04.090600), female, 178 mm TL. c. Brachyhypopomus belindae MCP 45430, paratype, immature, 104 mm TL (photographed out of water, close up of head not available). d. Brachyhypopomus bennetti MCP 45451, male, 196 mm TL. e. Brachyhypopomus brevirostris uncat., immature, 224 mm TL. f. Brachyhypopomus flavipomus MCP 45453 (WC09.090600), female, 98 mm TL. g. Brachyhypopomus hamiltoni MCP 45482 (WC05.080301), holotype, female, 97 mm TL. h. Brachyhypopomus hendersoni MCP 45489, female, 164 mm TL. i. Brachyhypopomus pinnicaudatus MCP 45455, female, 135 mm TL. j. Brachyhypopomus regani, MCP 45285 (WC02.100301), male, 119 mm TL. k. Brachyhypopomus sullivani MCP 45464 (WC04.210201), immature, 79 mm TL. l. Brachyhypopomus walteri MCP 45458 (WC 03.090600), male, 161 mm TL. m. Microsternarchus bilineatus uncat., 85 mm TL.

Fig. 43. Brachyhypopomus sullivani. MUSM 39624 (WC48.210709), holotype, female, 108 mm TL (head in lateral view, and body in lateral and dorsal view, specimen fixed in formalin and preserved in EtOH); Peru, río Ucayali, Amazonas dr. Scale bars = 5 mm.

Fig. 44. Collection records for Brachyhypopomus sullivani (circles). Holotype location is marked with an open symbol. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).