Hypostomus

Key to the species of Hypostomus from rio Ribeira de Iguape basin

1. Keels absent or poorly developed; anterior plates of mid-dorsal series longitudinally aligned with those of posterior portion of trunk, not interrupted by the first plate of dorsal series (Fig. 1A); caudal peduncle trapezoid in cross-section; 3 to 5 plates around supraoccipital (Fig. 2)............................................................ Hypostomus agna

1’. Keels well developed; anterior plates of mid-dorsal series not aligned with those of posterior portion of trunk, interrupted by the first plate of dorsal series (Fig. 1B); caudal peduncle ovoid in cross-section; 1 to 2 plates around supraoccipital.....................2

2. Plates on ventral surface of head absent in adults; spots on posterior half of body less conspicuous and more sparsely distributed than on anterior portion of body; spots on fins usually aligned, sometimes forming dark bands (Fig. 4).................. Hypostomus ancistroides

2’. Ventral region of head completely covered with dermal ossifications, except for small naked areas; pattern of distribution of spots on body and fins relatively uniform, never forming dark bands.......................................................................................................3

3. Presence of oblique inconspicuous dark bands on flanks; small spots over body and fins, smaller over head; dorsal fin comparatively smaller (dorsal-fin spine length 21.6 -28.4% SL) (Fig. 6)................................................................. Hypostomus interruptus

3’. Dark bands on flanks absent; well defined large, dark, and roundish spots somewhat homogeneously distributed over body and fins; relatively broad dorsal-fin (dorsal-fin spine length 27.6-34.3% SL) (Fig. 7).................................. Hypostomus tapijara, sp.n.