Pseudolaguvia magna is diagnosed from all species of the genus Pseudolaguvia by the possession of the following unique characters: larger body (up to 4.7 cm SL vs. a maximum of 3.56 cm SL); mid-dorsal region with two pale-brown to cream patches (one rectangular to elliptical patch on mid-interdorsal region, and another indistinct elliptical patch in between the adipose and caudal fins); broader rhomboidal thoracic adhesive apparatus; small pale-brown to cream round spot on the ventrolateral side of the head, almost perpendicular to the eye; and absence of pale-brown to cream-colored cross-bands on the body (which it shares with P. inornata, P. austrina, P. virgulata and P. assula) (Ref. 98400).

Description: Dorsal-fin rays 5,i; anal-fin rays iiv,4,i; iv,5; iii,5,i; iii,7,i; pectoral-fin rays i,5 or i,5,i ; pelvic -fin rays i,5 or i,5,i (Ref. 98400).