Color based differential key of Baryancistrus species (for living and preserved specimens):

1. Body uniformly dark or with faint light dots ..................... 2

1’. Body largely covered by conspicuous yellow or light dots .......................................................................................... 4

2. Presence of a continuous light band (bright yellow in living specimens) on border of dorsal and caudal fins.………................. Baryancistrus chrysolomus (rio Xingu)

2’. Dorsal and caudal fins without light terminal bands ...... 3

3. Body uniformly dark without any dots (small sized fishes, up to 80.9 mm SL) ..... Baryancistrus beggini (río Orinoco)

3’. Body covered with small and inconspicuous light dots of different sizes (but always smaller than pupil): larger on head, body and fin rays, and minute on interradial membranes (large fishes, up to 206.4 mm SL) ............................ Baryancistrus longipinnis (rio Tocantins)

4. Light dots covering only the anterior portion of body (to dorsal fin), posterior portion of body and fins plain ............................... Baryancistrus demantoides (río Orinoco)

4’. Light dots covering whole body ......................................... 5

5. Presence of light band (bright yellow in living specimens) on border of dorsal and caudal fins, broader in juveniles, and reduced to light markings on distal tips of dorsal and caudal in adults .......... Baryancistrus xanthellus (rio Xingu)

5’. Absence of light band on border of dorsal and caudal fins in juveniles and adults ......................................................... ........ Baryancistrus niveatus (rios Araguaia and Tocantins)