A new species of gymnorhamphichthys (Gymnotiformes: Rhamphichthyidae) from the paranparaguay basin

Gymnorhamphichthys britskii, new species, is described from the Paraná̃Paraguay system. The new species is distinguished from all other congeners except G. hypostomus in having 5-16 (usually 9-13) large dark saddle-shaped pigment bars over the dorsal midline, extending between the nape and a vertical with the end of the anal fin, and sometimes reaching to or slightly below the lateral line. The new species differs from G. hypostomus in having 141-172 vs. 178-211 anal-fin rays; a shorter snout, preorbital distance 48.1-60.3% of head length (mean 54.6%) vs. 58.3-68.6% (mean 63.9%); a larger eye, diameter 5.7-9.0% of head length (mean 7.0%) vs. 3.3-5.9% (mean 4.3%); a longer distance from tip of snout to posterior nares, 17.1-22.0% of head length (mean 19.2%) vs. 11.2-17.1% (mean 13.8%); 7 vs. 9-13 displaced hemal spines; and 64-69 vs. 71-75 vertebrae to end of anal fin.