Leuenberger, B. E.: The type specimen of Opuntia cardiosperma (Cactaceae), new synonyms and new records from Argentina and Paraguay. — Willdenowia 31: 171–179. 2001. — ISSN 0511-9618.

The type specimen of Opuntia cardiosperma (Cactaceae) from Paraguay, extant in the spirit collection of the Berlin-Dahlem herbarium, is illustrated. Comparison with unidentified specimens from Paraguay and northern Argentina revealed that the species is widespread but has been confused with O. paraguayensis. An amplified description of O. cardiosperma is provided. O. chakensis and O. mieckleyi are treated as new synonyms of O. cardiosperma.