Tympanopleura rondoni is distinguished by having more robust body shape and larger maximum size (about 160 mm SL) than congeners (all less than 120 mm SL in the material examined). It possesses a unique, prominently spotted pigmentation pattern on the head,

body, and fins, and an elongated gas bladder with two moderately long, recurved terminal posterior diverticula. It can be further diagnosed from T. atronasus in having a greater number of anal-fin rays (28-37, mode 31 vs. 23-30, mode 27), more pectoral-fin rays (10-13 vs. 7-9), more gill rakers on the first arch (24-33 vs. 14-23), fewer preanal vertebrae (14-16, mode 15 vs. 16-19, mode 17), fewer pairs of pleural ribs (4-6 vs. 7-8), greater distance from pectoral- to dorsal-fin origin (19.8-29.0% SL vs. 15.7-20.9% SL), slightly greater body width at pectoral-fin origin (21.8-29.5% SL vs. 17.8-22.9% SL), slightly longer pectoral-fin spine (17.1-21.0% SL vs. 13.3-19.0% SL), and a smaller eye diameter (8.4-17.0% HL vs. 16.0-27.8% HL). It differs from T. brevis in having more gill rakers (24-33, mode 29-30 vs. 20-24, mode 23), a slightly shorter-pectoral fin spine (17.1-21.0% SL vs. 19.1- 24.4% SL), and a smaller eye (8.4-17.0% HL vs. 13.8-21.0% HL); otherwise, these two species are differentiated mainly on the basis of pigmentation pattern and structure of the gas bladder. It is dintict from T. cryptica in having a longer anal fin (anal-fin rays 28-37, mode 31 vs. 23-30, mode 29), more pectoral-fin rays (10-13, mode 11 vs. 8-10, mode 9), more gill rakers (24-33, mode 29-30 vs. 21-26, mode 22), greater number of total vertebrae (38- 42, mode 40 vs. 38-41, mode 38), pleural rib pairs (4-6, mode 6 vs. 4-5, mode 5), and a smaller eye (8.4-17.0% HL vs. 16.7-25.6% HL). It can be separated from T. longipinna in having a somewhat shorter anal fin (anal-fin rays 28-37, mode 31 vs. 32-42, mode 37), more gill rakers (24-33, mode 29-30 vs. 19-25, mode 23), fewer total vertebrae (38-42, mode 40 vs. 40-43, mode 43), pleural rib pairs (4-6, mode 6 vs. 4-5, mode 5), longer predorsal length (35.2-47.4% SL vs. 29.5-36.1% SL), shorter distance from pelvic- to adipose-fin origin (24.0-41.5% SL vs. 37.6-45.1% SL), shorter distance from dorsal- to adipose-fin origin (38.1-46.8% SL vs. 46.5-54.0% SL), and a shorter anal-fin base (23.1-32.5% SL vs. 33.9-39.9% SL). It is distinguisged from T. piperata in having more pectoralfin rays (10-13, mode 11 vs. 6-10, mode 9), more gill rakers (24-33 vs. 16-23), pleural ribs pairs (4-6, mode 6 vs. 4-5, mode 4), longer prepectoral length (29.2-39.0% SL vs. 23.6-28.3% SL), greater distance from pectoral- to dorsal fin origin (19.8-29.0% SL vs. 15.2-20.9% SL), greater body width at pectoral-fin origin (21.8-29.5% SL vs. 16.8-20.0% SL), shorter anal-fin base (23.1-32.5% SL vs. 30.9-39.3% SL), longer head (26.5-39.0% SL vs. 22.2-27.8% SL), longer snout (41.7-53.6% SL vs. 31.4-43.6% SL), proportionally longer jaws and a wider gape, and a smaller eye (8.4-17.0% HL vs. 24.3-35.7% HL) (Ref. 103256).