Callichthyidae

Callichthyidae is a family of catfishes (order Siluriformes), called armored catfishes due to the two rows of bony plates (or scutes) along the lengths of their bodies. It contains some of the most popular freshwater aquarium fish, such as many species in the genus Corydoras. The family derives its name from the Greek words kallis (beautiful) and ichthys (fish). Callichthyidae is one of six families in the superfamily Loricarioidea, and is sister to a clade formed by Scoloplacidae, Astroblepidae, and Loricariidae. Within the family Callichthyidae, the two subfamilies have eight genera and about 177 species, accounting for about 7% of all catfish. Most of these species are in the genus Corydoras, the largest catfish genus. The subfamily Corydoradinae includes about 90% of the species in the family Callichthyidae and is one of the most diverse siluriform assemblages in the Neotropics, with about 170 valid species. It includes two tribes, Aspidoradini and Corydoradini. Aspidoradini contains Aspidoras and Scleromystax, while Corydoradini contains Corydoras and Brochis. Some believe the genus Brochis should be synonymized with Corydoras. The subfamily Callichthyinae contains Callichthys, Dianema, Hoplosternum, Lepthoplosternum, and Megalechis. According to a 1997 paper, Callichthys is the most basal member of the subfamily. In a 2004 study, different relationships among the callichthyines were found: Dianema and Hoplosternum form the most basal clade, and Callichthys is sister to Lepthoplosternum and Megalechis. The first known fossil species of callichthyid is Corydoras revelatus from Salta, Argentina, of the late Paleocene. This species is tentatively placed in Corydoras, but is unambiguously a member of the subfamily Corydoradinae. It indicates that the lineages leading to the two callichthyid subfamilies occurred at least by the late Paleocene. It also suggests an earlier differentiation of loricarioids in comparison to other catfishes, or a lack of older fossils of other Neotropical groups. A fossil identified as a Hoplosternum species has also been identified from the middle Miocene in the La Venta formation, Magdalena River basin, Colombia. The Neotropical family Callichthyidae is found in most South American river drainages (Paraná-Paraguay, São Francisco, Atlantic Coastal basins in Brazil, Amazon, Orinoco, Maracaibo, Magdalena). Hoplosternum punctatum is the only species in Central America, as it occurs in a few rivers in Panama. Callichthyidae present the highest species richness in the headwaters of the Amazonas drainage and those rivers draining the Guiana Shield. The subfamily Corydoradinae is found east of the Andes and north of the Rio de La Plata system. Representatives of the Corydoradinae are found in several freshwater environments, ranging from fast-flowing piedmont streams with sandy or rocky bottoms to lowland pools with muddy bottoms. A single species, Aspidoras mephisto, is a cavefish.