Typification of Mexican Euphorbia (Euphorbiaceae) Author Steinmann, Victor W. 0000-0003-0103-9575 Instituto de Ecología, A. C., Centro Regional del Bajío, Av. Lázaro Cárdenas 253, 61600 Pátzcuaro, Michoacán, Mexico. steinmav@gmail.com text Phytotaxa 2023 2023-12-12 630 1 61 68 https://phytotaxa.mapress.com/pt/article/download/phytotaxa.630.1.5/51357 journal article 10.11646/phytotaxa.630.1.5 1179-3163 10361687 Euphorbia mendezii Boissier (1860: 15) . ≡ Chamaesyce mendezii (Boissier) Millspaugh (1916: 410) . Lectotype (designated here):— MEXICO . Guanajuato : Léon a ouest de Guanajuato, 1829, J. Méndez 419 ( G-DC barcode G00310747 photo!, branches “6” and “7”). This common New World annual with weedy tendencies was first described from material collected in central Mexico by J. Méndez in 1829. The protologue provides a detailed morphological description and includes the statement “cl. Mendez in DC. herb.!.” According to Rogers McVaugh (pers. comm. 2001), who carefully studied the original material in 1993, the “ holotype ” sheet at D-GC is a mixed collection of Euphorbia mendezii (as the name is consistently applied and corresponding to Boissier’s description, see Turland et al. (2018) , Art. 9.14) and Euphorbia velleriflora (Klotzsch & Garcke (1860: 28)) Boissier in Candolle (1862: 40). This is evident from images available at the Geneva Herbarium Catalogue (https://www.ville-ge.ch/musinfo/bd/cjb/chg/index.php?lang=en). In fact, of the eight branches present, only two of them represent E. mendezii . These are labelled “6” and “7.” McVaugh proposed lectotypifying the name with the two branches in an unpublished manuscript on the genus Euphorbia in the region of Nueva Galicia, Mexico . However, since McVaugh’s lectotypification was never formally made before his death in 2009, it is done so here.