Pycreus decumbens, described from Brazil, is noted as a synonym of the Old World species, Cyperus mundtii; a new name is provided for the eastern Brazilian Cyperus palustris; C. affinis is determined to be the correct name for Cyperus comosus (a relative of C. giganteus) and C. spicigerus is noted as an older name for C. schoenomorphus.
Tucker, G. C., & Gandhi, K. (2013). Nomenclatural Notes on Neotropical Cyperus (Cyperaceae). Harvard Papers in Botany, 18(2), 149–154. https://doi.org/10.3100/025.018.0209