Diagnosed from all other species of Tatia by the following characters: male anal fin with sharp pointed tip; the first unbranched anal-fin ray divided into 3-4 segments; and the last branched ray reduced. Can be distinguished from most of its congeners, except Tatia aulopygia Tatia intermedia and Tatia gyrina, by having a wide mouth, width 54.0-59.7% HL (vs. 39.0-53.3% HL). Additional characteristics for recognition of Tatia brunnea are diagnostic in combination: nasal ossified with wide medial flanges partially sutured to lateral margin of mesethmoid; ribs 9-10; post-Weberian vertebrae 34-36. Other features useful for distinguishing Tatia brunnea include details in coloration, such as: border of mouth whitish, contrasting with dark head; posterior border of nuchal shield usually whitish or pale; pectoral-fin spine usually with transverse bands; caudal fin usually whitish with scattered dark brown blotches; and head width 86.6-93.4% HL (Ref. 79512).

Description: Anal fin iii,7, rarely iii,8; Pelvic fin i5; post-Weberian vertebrae 34-36 (Ref. 79512).