Key to species of Phalloceros:

1. Female urogenital papilla slightly left turned and with a lateral ramus (Fig. 16). Hooks of the gonopodial appendix large and sickle like (Figs. 14, 17, 20) ................................. 2

1’. Female urogenital papilla turned to the right (Fig. 52) or straight along midline (Fig. 53) Lateral ramus absent. Hooks of the gonopodial appendix absent or present, but never large and sickle like (e. g. Fig. 28) ....................................... 4

2. Lateral spot present .............................................................. 3

2’. Lateral spot absent ............................ Phalloceros aspilos (Rio Parati-Mirim drainage, Rio de Janeiro)

3. Lateral spot densely pigmented, rectangle like, horizontally covering the length corresponding to two or three scales length (Fig. 15) .............................. Phalloceros leptokeras (lower portions of rio Paraíba do Sul drainage)

3’. Lateral spot normally pigmented, vertically elongated, and horizontally covering the length corresponding to one scale length (Fig. 13) .................... Phalloceros tupinamba (rio Itamambuca and rio Macacu drainages)

4. Female urogenital papilla straight, located along midventral line and between the anus and the base of first anal-fin ray (Fig. 53) ................................................................................ 14

4’. Female urogenital papilla curved to the right, located laterally (Fig. 52). Border of the anal aperture in contact with the first anal-fin ray or very close to it .............................. 5

5. Caudal peduncle spot absent .............................................. 6

5’. Caudal peduncle spot present (Fig. 48) .................................... ............................................................. Phalloceros spiloura (Rio Tubarão, rio Itajaí-Açu, rio Iguaçu, rio Itapocu, rio Mampituba, rio Cubatão [Norte], rio Tramandaí drainages, coastal drainages of Rio Grande do Sul e Santa Catarina)

6. Gonopodium appendix normally developed, not expanded in wing like projections ........................................................ 7

6’. Gonopodium appendix greatly expanded in wing like projections (Fig. 37) ........................... Phalloceros megapolos (drainages of the rio São João, rio Cubatão [Norte] and small adjacent drainages, which flows to the Baía de Guaratuba in Santa Catarina)

7. Halves of gonopodial paired appendix slender, not sickle like, and similar to each other, bearing a medial corner. Hook on both halves of gonopodial paired appendix. Both hooks large, downward directed, and located at the corner of gonopodial appendix (Figs. 33, 35) ..................................... 8

7’. Halves of gonopodial paired appendix sickle like; medial corner absent. Hook on left half of gonopodial paired appendix only. Right hook absent. Left hook small, directed downward or up- and forward, and located close to the base of gonopodial appendix (Figs. 39, 43, 45, 47, 51) ...... 9

8. Gonopodial appendix long and strongly arched at the distal tip. Distal portion bent upward. Left and right halves free not coalescent at the base (Fig. 35) ........................ ........................................................... Phalloceros malabarbai (Itapoá, Santa Catarina)

8’. Gonopodial appendix long and straight at the distal tip. Distal portion straight and oblique, forming a 45 º angle with the vertical axis. Left and right halves coalescent at the base (Fig. 33) ....................... Phalloceros alessandrae (flooded areas on margins nearby Antonina [Paraná] and rio Dois de Fevereiro, which flows into the Baía de Paranaguá)

9. Halves of gonopodial paired appendix wide and distinct from each other; right half wider than left one (Figs. 39, 41, 45, 47, 51) ............................................................................. 10

9’. Halves of gonopodial paired appendix slender and similar to each other (Fig. 43) ...................... Phalloceros buckupi (rio Jacareí drainage and neighbouring, which flows to the Baía de Paranaguá in the coast of Paraná State of Brazil)

10. Lateral spot of large specimens absent or when present narrow, elliptical to roundish, or vertically elongated but never square-shaped (Figs. 38, 44, 46, 50) ....................... 11

10’. Lateral spot wide and square-shaped in large specimens (Fig. 40) ....................................................... Phalloceros uai (rio das Velhas, rio São Francisco)

11. Hook on left half of gonopodial appendix with a rounded or pointed tip (Figs. 45, 47, 51) ........................................... 12

11’. Hook on left half of gonopodial appendix with a rectangular tip (Fig. 39) .......................... Phalloceros lucenorum (rio Juquiá drainage)

12. Hook on left half of gonopodial appendix located approximately midway to the distal third of gonopodial appendix (Fig. 51). Lateral spot of adult females absent, small, or elliptical to roundish, but never forming a vertical bar (Fig. 50) ......................................................................................... 13

12’. Hook on left half of gonopodial appendix near its tip, located approximately between distal quarter and distal third of gonopodial appendix (Fig. 45). Lateral spot of adult females very narrow, forming a vertically elongated bar covering at most the length corresponding to two scales length in horizontal direction and 2-4 scales in vertical direction (Fig. 44) ......................... Phalloceros anisophallos (drainages of rio Parati, rio Barra Grande, rio São Roque and rio Itinguçu - small coastal drainages of the State of Rio de Janeiro)

13. Hook on left appendix very small, visible only in large males and under a high magnification (Fig. 47). Lateral spot always present and evident, not covering more than two scales in horizontal or vertical directions (Fig. 46) ............. ............................................................... Phalloceros pellos (Paranaguá, Paraná)

13’. Hook on left appendix larger (Fig. 51). Lateral spot absent or small and discrete not covering the length corresponding to one or two scales length in horizontal or vertical directions (Fig. 50) ................................. Phalloceros reisi (headwaters of rio Tietê, rio Paraíba do Sul, and rio Ribeira de Iguape)

14. Well-defined ocellated lateral spot, roundish to rounded (very rarely absent) (Figs. 2, 5, 30) .................................... 15

14’. Non-ocellated lateral spot, elliptical, vertically elongated, or absent (Figs. 8, 10, 21, 23, 25, 27) ................................... 17

15. Ten, rarely 9, anal-fin rays in females ............................. 16

15’. Eleven anal-fin rays in females.................................. .................................................... Phalloceros mikrommatos (rio João de Tiba drainage, a coastal drainage in the Bahia State)

16. Postorbital length 39.2-42.2 % SL (females) and 36.7-42.3 % SL (males) ....................................... Phalloceros leticiae (the upper rio Araguaia)

16’. Postorbital length 24.8-39.3 % SL (females), and 29.3-38.2 % SL (males) ................................... Phalloceros ocellatus (coastal drainages of Bahia and Espírito Santo States between Prado and Sooretama)

17. Gonopodial appendix hook absent (Fig. 10) .................. 18

17’. Gonopodial appendix hook present (Fig. 28) ................. 19

18. Sexual dimorphism on number of dorsal-fin rays: males with 8 rays (very exceptionally seven) and females with seven rays (very exceptionally 8). Lateral spot absent (Fig. 9) ................................................... Phalloceros heptaktinos (tributaries of arroio dos Ratos, Jacuí basin, in Mariana Pimentel, Rio Grande do Sul)

18’. Eight dorsal-fin rays in both sexes. Lateral spot usually present ................................. Phalloceros caudimaculatus (laguna dos Patos system, drainages of rio Ibicuí and Negro [affluent to rio Uruguai], Tramandaí, Mampituba, coastal drainages of Rio Grande do Sul, Uruguay and Argentina).

19. Eight dorsal-fin rays (very rarely seven or nine) ........... 20

19’. Nine dorsal-fin rays ........... Phalloceros enneaktinos (córrego da Toca do Boi, Rio de Janeiro)

20. Symphyseal papillae absent ............................................ 21

20’. Symphyseal papillae present (Fig. 26) ..................... ................................................................ Phalloceros titthos (coastal drainages flowing to Baia de Guaratuba and Baia de Paranaguá in Paraná State)

21. Small size. Appendix hook minute in adults, forming a lateral minute protuberance (Fig. 22). Hook absent or tiny (rarely) in juveniles, never situated on the appendix corner. Juveniles never with skin covering the tip of appendix. Distal half of appendix approximately as wide as (or slightly narrower than) proximal half (Fig. 22) ....................... .......................................................... Phalloceros elachistos (drainages of rio Doce, rio Santa Maria da Vitória, rio Jucu, and rio Timbuí, coastal drainages of Espírito Santo)

21’. Small to large size. Appendix hook medium or large in adults (Fig. 28). Hook present in juveniles and located on the appendix corner. Juveniles with skin covering the tip of appendix. Distal half of appendix conspicuously narrower than proximal half (Fig. 28) ...................... ........................................................... Phalloceros harpagos (Rio Paraná-Paraguai basin and coastal drainages from rio Itaboapana in Espírito Santo to rio Araranguá in Santa Catarina)