The genus was formerly circumscribed to include 25 species. A molecular phylogenetic study found that circumscription to include four distinct lineages:
a group largely conforming to subgenus Lophoschoenus (eight species) from New Caledonia and
Malesia that are now considered to be part of a redelimited genus Tetraria.
In 2019, the genus was revised to include 15 species, generally corresponding to Costularia s.s. and including a few previously undescribed species.[6]
^Govaerts, R. & Simpson, D.A. (2007). World Checklist of Cyperaceae. Sedges: 1-765. The Board of Trustees of the Royal Botanic Gardens, Kew.
^Hoenselaar, K., Verdcourt, B. & Beentje, H. (2010). Cyperaceae. Flora of Tropical East Africa: 1-466.
^Strugnell, A.M. (2006). A checklist of the Spermatophytes of Mt. Mulanje, Malawi. Scripta Botanica Belgica 34: 1-199.
^
abLarridon I, Rabarivola L, Xanthos M, Muasya AM. 2019. Revision of the Afro-Madagascan genus Costularia (Schoeneae, Cyperaceae): infrageneric relationships and species delimitation. PeerJ 7:e6528
https://doi.org/10.7717/peerj.6528