The species was originally described in the year 1893 by the physician, naturalist and writer Argentine Eduardo Ladislao Holmberg, under the scientific term for Liposarcus ambrosettii using samples caught in the Paraguay River, opposite the city of Formosa. It is included in the Hypostominae subfamily.[6]
Etymologically, the generic name Pterygoplichthys is constructed with three words of the Greek language, where: pterygion is the diminutive of pteryx that means 'fin', hoplon is 'weapon', and ichthys is 'fish'.[7] The specific term ambrosettii honors the surname of Argentine naturalist Juan Bautista Ambrosetti.[8]
Pterygoplichthys anisitsi was described in 1903 by the German-American ichthyologist Carl H. Eigenmann along with Clarence Hamilton Kennedy.[9] These scientists were originally credited more so with its discovery since the description made by Holmberg went unnoticed, so in 1992 C. Weber passed the latter to the category of nomen oblitum.[10] However, the epithet of P. ambrosettii had been cited as the valid name for this fish by Isaäc Isbrücker in 1980.[11] Other authors began to agree, so in 2007 Carl J. Ferraris Jr. determined that, being the oldest available name, it corresponds to being the senior synonym, becoming P. anisitsi to be its minor synonym.[4]
