[[Genus Isbrueckerichthys Derijst ^ZBK ]]

Key to the species of Isbrueckerichthys ^ZBK

1 Teeth of dentary and premaxilla without lateral cusp ..................................................... .................................................................... I. alipionis (Ribeira de Iguape River basin)

- Teeth of dentary and premaxilla with small lateral cusp ............................................... 2

2. Mature males with a clump of hypertrophied odontodes only on anterior portion of snout ........................................................... I. epakmos ^ZBK (Ribeira de Iguape River basin)

- Mature males with hypertrophied odontodes along the lateral margin of head ............ 3

3. Short pectoral-fin spine (17.3-21.4 % SL) and long caudal peduncle length (34.6-38.2 % SL) ............................................................. I. duseni (Ribeira de Iguape River basin)

- Long pectoral-fin spine (21.5-27.4 % SL) and short caudal peduncle length (26.4-30.0 % SL) ......................................................................................................... 4

4. Minute abdominal platelets with much more than six odontodes; plated area under the first three plates of the lateral line; exposed portion of cleithrum bordering all the posterior margin of the opercular opening on lateral side of the body; exposed surface of supraoccipital plane or slightly convex ............... I. saxicola sp. n. ( Paraná River basin)

- Minute abdominal platelets with at most six odontodes; nude area under the first three plates of the lateral line; cleithrum not exposed, or when exposed, bordering just the superior portion of posterior margin of the opercular opening on lateral side of the body; exposed surface of supraoccipital strongly convex, with an area without odontodes at the center ................................................... I. calvus sp. n. ( Paraná River basin)