Gymnotus pantanal differs from other members of the G. pantherinus species-

group (except G. anguillaris) in possessing a color pattern composed of thin obliquely oriented pale pigment bands (about one third the width of the dark bands) with wavy margins restricted to the ventral portion of the body (rarely extending above the lateral line) on

the anterior half of the body. Gymnotus pantanal further differs from other members of the G. pantherinus species-group in possessing a wider head (72–77 vs. 52–69% head length). Gymnotus pantanal further differs from G. anguillaris in possessing more narrowly set eyes (37–41 vs. 43–56% head length), a deeper head (66–74 vs. 60–65% head length), larger branchial openings (38–43 vs. 29–36% head length), longer pectoral fins (51–56 vs.

42–50% head length), more pectoral-fin rays (mode 17 vs. 16), and fewer pored posterior

lateral-line scales (to first ventral ramus: 47–58 vs. 58–62; total: 102–114 vs. 124–130).