1a. Dorsal face of lateral ethmoid bearing a segment of the supraorbital latero-sensory canal; preopercle covered with skin; dentary with teeth; nuchal plate covered with skin; snout depressed; maxillary barbel long, usually passing the gill opening (Callichthyinae) .....2
1b. Dorsal face of lateral ethmoid without latero-sensory canal; preopercle exposed; dentary without teeth; nuchal plate exposed; snout compressed; maxillary barbel short, usually not passing the eye (Corydoradinae) .....6
2a. Infraorital bones covered with skin; head very depressed, less than 75% of cleithral width, coracoids not exposed ventrally .....Callichthys
2b. Infraorbital bones exposed; head moderately depressed, more than 75% of cleithral width; coracoids exposed ventrally .....3
3a. Caudal fin bifurcated or concave .....4
3b. Caudal fin truncated or convex .....5
4a. First infraorbital bone weakly connected to the lateral ethmoid; dorsal-fin spine as long as the first branched ray .....Dianema
4b. First infraorbital bone articulated to the lateral ethmoid; dorsal-fin spine about half the length of the first branched rays .....Hoplosternum
5a. Dorsal fin with one short spine, one unbranched ray and 7-8 branched rays; anal fin with two unbranched and 5-6 branched rays; mature males with a very elongate pectoral-fin spine .....Megalechis
5b. Dorsal fin with one spine and seven branched reys; anal fin with one unbranched and five branched rays; mature males with pectoral-fin spines thickened but not especially elongated .....Lepthoplosternum
6a. Roundish supraoccipital fossa present; ossified portion of pectoral- and dorsal-fin spines short, about half length of first branched ray; nuchal plate not in contact with the supraoccipital posterior process .....Aspidoras
6b. Supraoccipital fossa absent; ossified portion of pectoral- and dorsal-fin spines about as long as the subsequent branched rays; nuchal plate in contact with the supraoccipital posterior process .....7
7a. Dorsal fin with 7-9 branched rays .....Corydoras
7b. Dorsal fin with 10-18 branched rays .....Brochis
