Key to species of Paracanthocobitis in the P. zonalternans complex

1. Dark marmorated pattern between dorsal saddles and lateral blotches; teardrop-shaped (vs. circular or triangular) black spot on upper margin of caudal-fin base................................................................ P. marmorata

- No dark marmorated pattern between dorsal saddles and lateral blotches; circular or triangular black spot on upper margin of caudal-fin base........................................................................................2

2. No black pigment extending from black lateral stripe or blotches onto pectoral-fin base..............................3

- Black pigment extending from black lateral stripe or blotches onto pectoral-fin base.................................4

3. Axillary pelvic lobe present; triangular black spot on upper margin of caudal-fin base...................... P. triangula

- Axillary pelvic lobe usually absent, occasionally rudimentary; circular black spot on upper margin of caudal-fin base................................................................................................. P. phuketensis

4. Series of black blotches, usually with stripe absent or dusky and ending near the dorsal-fin insertion; minimum HL 17% of SL......................................................................................... P. zonalternans

- Black stripe along side of body ending near caudal fin and overlaying lateral blotches; minimum HL 19% of SL.................................................................................................... P. nigrolineata