Oxypetalum Brown (1810: 30), nom. cons.

Type: O. banksii Schultes (1820: 91) .

Gothofreda Ventenat (1808: t. 60), nom. rej.

Schistogyne Hooker & Arnott (1834: 291) . Type: S. sylvestris Hooker & Arnott (1834: 292) . Synon. nov.

Calostigma Decaisne (1838: 343) . Type: C. insigne Decaisne (1838: 344; t. 12, f. H).

Schizostemma Decaisne (1838: 344) . Type: non designatus.

Pachyglossum Decaisne (1838: 345) . Type: non designatus.

Bustelma Fournier (1885: 287) . Type: B. warmingii Fournier (1885: 287) .

Dactylostelma Schlechter (1895: 452) . Type: D. boliviense Schlechter (1895: 452) .

Corollonema Schlechter (1914: 441) . Type: C. boliviensis Schlechter (1914: 441) .

Amblyopetalum Malme (1927: 2) . Type: A. coccineum (Grisebach 1874: 206) Malme (1937: 8) .

Metoxypetalum Morillo (1994: 145) . Type: M. retusum (Markgraf 1933: 787) Morillo (1994: 146) .

Note:— Oxypetalum is the largest genus of Oxypetalinae, including around 120 species, distributed from Argentina to Mexico, with the centre of diversity in central-eastern South America. Most species are characterised by a combination of flowers with lanceolate corolla lobes, corona lobes gynostegial in origin but displaced onto the base of the corolla, free above and adaxially ornamented, style-head forming a rostrate appendage at the apex of gynostegium simulating a stigma, and caudicles of pollinaria with lateral teeth. Schistogyne was created based on the unusual appendage of the style-head with seven linear lobes in S. sylvestris: ‘ Stygma sub-7-partitum (!), segmentis subulato-filiformis.’ (Hooker & Arnott 1834: 292), and with gynostegial corona lobes in a staminal position. Variations of the style-head appendage were used to recognise some genera currently considered synonym of Oxypetalum (e.g., Calostigma). Nevertheless, this is a polymorphic structure and variations are found even in closely related species. For instance, O. pilosum Gardner (1842: 539) exhibits style-head terminating in a rostrate appendage, whereas O. erostre Fournier (1885: 265), which is the closest species and was eventually considered synonym of the former (Valente et al. 1973), exhibit a conical style-head lacking an appendage.

Besides confirming the inclusion of Amblyopetalum, Bustelma and Dactylostelma in the synonymy of Oxypetalum, phylogenetic studies of plastid regions (Rapini et al. 2003, Liede-Schumann et al. 2005) also showed Schistogyne nested in core Oxypetalum, closely related to O. banksii . To become monophyletic, Oxypetalum must include Schistogyne . Below, we provide the combinations for the eight accepted species of Schistogyne in Oxypetalum, designate lectotypes for three species and indicate a new synonym.