Spatuloricaria tuirais distinguished from all other congeners except Spatuloricaria nudiventris by its abdominal surface completely naked or rarely with few, very small plates (vs. abdominal region covered with plates) and by the absence of preanal plates (vs. presence of one to four preanal plates). It can be differentiated from S. nudiventris and S. fimbriata by having five transversal dark brown bands on the dorsal region (vs. four transversal dark brown dorsal bands in S. nudiventris and S. fimbriata) and by having dark-brown irregular stripes on the dorsal region of the head and predorsal area (vs. absence of such stripes in S. nudiventris and S. fimbriata). This species has the smallest males recorded among species of Spatuloricaria, with mature individuals ranging from 8.55 to 15.39 cm SL and seems to be the only one in the genus where mature males are smaller than mature females (the opposite is the case in other species of Spatuloricaria). However, additional materials of some of the other species are needed to further verify these observations (Ref. 96500).

Description: Dorsal-fin rays i,7; anal-fin rays i,5; pectoral-fin rays i,6; pelvic-fin rays i,5 (Ref. 96500).