Apteronotus

Carlos David de Santana, 2003, Apteronotus caudimaculosus n. sp. (Gymnotiformes: Apteronotidae), a sexually dimorphic black ghost knifefish from the Pantanal, Western Brazil, with a note on the monophyly of the A. albifrons species complex., Zootaxa 252, pp. 1-11 : 6-8

[[ Apteronotus ]]

A dichotomous key to species of Apteronotus (sensu stricto)

(Specimens over 100.0 mm TL)

1 Body coloration even or finely spotted ......................................................................... 3

- Body coloration blotchy or marbled .............................................................................. 2

2 Mouth rictus passing imaginary vertical line at posterior naris; clear band on dorsal region of body; specimens less than 140.0 mm TL with two clear bands on caudal fin peduncle; those over 140.0 mm TL with one clear band encircling base of caudal fin. Distribution: Maracaibo basin, Venezuela .............................. A. cuchillo Schultz, 1949

- Mouth rictus not passing imaginary vertical line with posterior naris; dorsal region evenly colored; clear band encircling base of caudal fin in large specimens. Distribution: Magdalena basin, Colombia ............................... A. magdalenensis (Milles, 1945)

3 Presence of one clear band encircling caudal fin peduncle throughout development ............ 5

- Presence of two clear bands encircling caudal fin peduncle throughout development... ..................................................................................... 4 ( A. albifrons species complex)

4 Absence of spots on first clear band on caudal peduncle; long tail 22.3-23.1% of LEA. Distribution: Surinam ....................................................... A. albifrons (Linnaeus, 1766)

- Irregular spots on first clear band on caudal peduncle throughout development; short tail 10.4-19.2% of LEA. Distribution: Pantanal, central Brazil ...................................... ................................................................................................. A. caudimaculosus n. sp.

5 Presence of clear band on dorsal region of body .......................................................... 6

- Absence of clear band on dorsal region of body ........................................................... 9

6 Seven transitional vertebrae. Distribution: Maracaibo basin, Venezuela ........................ ........................................................................................... A. cuchillejo (Schultz, 1949)

- Three to four transitional vertebrae ............................................................................... 7

7 Presence of clear band on chin ...................................................................................... 8

- Absence of clear band on chin. Distribution: Magdalena basin, Colombia .................... ........................................................................ A. mariae (Eigenmann and Fisher, 1914)

8 Two rows of teeth on dentary; maxilla without conspicuous ascending process in dorsoposterior region; twelve scales above lateral line at mid-body. Distribution: Basins of the Guyana shield ............................. A. leptorhynchus species complex (Ellis, 1912)

- Two rows of teeth on anterior part of dentary and one row on posterior portion; maxilla with conspicuous ascending process in dorsoposterior region; nine to ten scales above lateral line at mid-body. Distribution: Magdalena basin, Northern basins of Colombia and Panama ...... A. rostratus species complex (Meek and Hildebrand, 1913)

9 Mouth rictus reaching an imaginary vertical line with eyes ....................................... 10

- Mouth rictus not reaching an imaginary vertical line with eyes ................................. 11

10 Five to eight scales above lateral line at mid-body. Distribution: Paraná and Paraguay River basins ........................................................................... A. ellisi ( Aramburu, 1957)

- More than nine scales above lateral line at mid-body. Distribution: Rio Jurubidá, Nuquí (Colombia) .............................................................. A. jurubidae (Fowler, 1944)

11 Mouth rictus passing an imaginary vertical line at posterior naris; dorsum covered by scales; 12 to 16 scales above lateral line at mid-body; two rows of teeth on dentary. Distribution: São Francisco, Paraná and Parnaíba river basins ....................................... ......................................................... A. brasiliensis species complex (Reinhardt, 1852)

- Mouth rictus not passing an imaginary vertical line at posterior naris; absence of scales on dorsal region of body; presence of enlarged fleshy lateral lobe on chin; eight scales above lateral line at mid-body; two to three rows of teeth on dentary. Distribution: Rio Paraná, Mato Grosso do Sul, Brazil ................................... A. marauna (Triques, 1998)