Nandus mercatus Ng 2008

No unique diagnostic character was found for this species, with a combination of the followingcharacters diagnosing it from all congeners: body depth 43.0–43.2% SL, 15 pectoral-fin rays, 29–32 lateral line scales, 11–12 scale rows below the lateral line, and slightly concave predorsal profile. Among Sundaic Southeast Asian congeners, Nandus mercatus is distinguished from N. nebulosus in having a slightly concave(vs. even or slightly convex) predorsal profile, rostral fossa reaching to almost half (vs. more than half) predorsal distance and fewer pectoral fin rays (15 vs. 17–19), and from N. prolixus in having fewer lateral-linescales (29–32 vs. 33–37) and deeper body (43.0–43.2% SL vs. 37.6–40.5). It differs from South Asian congeners N. andrewi and N. nandus in having fewer lateral line scales (29–32 vs. 42–55), fewer scale rows below the lateral line (11–12 vs. 14–18), and deeper body (43.0–43.2% SL vs. 24.3–37.1). Nandus mercatus is distinguished from N. oxyrhynchus in having fewer lateral-line scales (29–32 vs. 37–42) and a more gently-slopingpredorsal profile.

Dorsal spines (total): 14; Dorsal soft rays (total): 10; Anal spines: 3; Analsoft rays: 5 - 6; Vertebrae: 22

The single paratype of N. mercatus was obtained from streams draining into an ox-bow on the Musi River. The water was brown and of low pH (4.3)