Tweedia Hooker & Arnott (1834: 291). Lectotype: T. brunonis Hooker & Arnott (1834: 292). Turrigera Decaisne (1844: 590). Type: T. inconspicua Decaisne (1844: 590). Note:— Three species of Tweedia were listed by Hooker & Arnott (1834), and each of these has subsequently been designated by different authors as the lectotype of the genus. Although Malme (1904) revised the genus Tweedia and emended its concept, he did not indicate a type. The first to do so was T. Meyer (1944: 102), who chose T. brunonis as his “especie genérica” for Tweedia. Hooker & Arnott (1834) questioned the future generic placement of this species when they erected the genus and described the species. They listed two characters for the genus: the form of the corona, and the bifid style-head appendage. As their description of T. brunonis notes the stigma to be undivided, a “serious conflict” with the protologue could be argued, leading to a rejection of Meyer´s lectotypification under Art. 9.17 of the Code. But the apex of the style-head appendage is, in fact, shortly bilobed, as shown by Rua (1989). Nomenclaturally, Hooker & Arnott made the combination under Tweedia, and the taxonomic opinion expressed subsequently does not negate this. Bullock (1958: 99) was presumably unaware of Meyer’s typification when he designated T. macrolepis Hooker & Arnott (1834: 291) as type of the genus. Rua (1989) argued that Bullock's designation was arbitrary and therefore contrary to the code (although this does not stand up to scrutiny, and was a superfluous designation in any case). Rua selected T. birostrata (Hooker & Arnott 1830: 35) Hooker & Arnott (1834: 291), which Ezcurra (1999: 75) then followed in Flora Patagonica. The earliest designation is that of Meyer (1944) and must be adopted.

Published as part of Rapini, Alessandro, Pereira, Jorge Fontella & Goyder, David J., 2011, Towards a stable generic circumscription in Oxypetalinae (Apocynaceae), pp. 9-16 in Phytotaxa 26 on page 13, DOI: 10.11646/phytotaxa.26.1.2, http://zenodo.org/record/4894142