The tail-bar hoplo catfish, an armoured catfish of the family Callichthyidae. This site describes some nomencultural confusion (will I ever escape that?), but I'm not sure of the relative ages of the various bits of information. In any case, these guys are pretty cool, with full-body-armour formed of dermal bone. They're also apparently quite tolerant of poor water conditions, especially anoxia, and are popular aquarium pets. Members of this family gulp air from the surface, absorbing the oxygen through the intestinal wall, and using the gasses to help with buoyancy control.Here's a second photo from the same site (not English-language), just for fun.
Photo credit for both pictures here.
Tree of life information for the family here.