Pseudolaguvia fucosa is distinguished from congeners except for P. virgulata by the presence (vs. absence) of a pale, y-shaped marking on the dorsal surface of the head; from congeners except for P. flavida, P. kapuri, P. muricata, P. nepalensis, P. ribeiroi and P. virgulata by the presence (vs. absence) of serrations on the anterior edge of the dorsal spine. It differs from the remaining six species by a combination of the following characters: dorsal-fin spine length 18.0-21.6% SL; anterior edge of the dorsal spine with 4-10 serrations; pectoral-fin spine length 20.7-26.1% SL; adipose-fin base length 21.5-26.3% SL; body depth at anus 12.3-15.9% SL; caudal peduncle depth 7.5-9.8% SL; caudal peduncle length 17.0-20.5% SL; and sides of body with pale yellowish patches and irregular bands (Ref. 107791).