Simmondsiaceae Tiegh. ex Reveal & Hoogland in Bull. Mus. Natl. Hist. Nat., B, Adansonia Sér. 4, 12: 206. 1990 sec. APG III (2009)



A monotypic family native to the Sonoran Desert of northwestern Mexico and to neighbouring regions in Arizona and southern California (Vázquez-Yanes & al. 1999), it is also introduced in some countries of South America, Europe, Asia and Africa. The family includes evergreen dioecious shrubs with opposite and thick leaves, clearly articulated near the stem; the staminate flowers are small and borne in terminal inflorescences while the pistillate flowers are single and axillary; the calyx is much enlarged in fruit (Stevens 2001 onwards; Köhler 2003).
Traditionally, the family was placed in Hamamelidales (sensu Takthajan 1980), Euphorbiales (sensu Cronquist 1988) or in its own order Simmondsiales (sensu Takthajan 1997), in some cases within Buxaceae or close to it. However, the early molecular phylogenetic study by Fay & al. (1997) showed the affinities of Simmondsiaceae with Caryophyllales, this agrees also with several morphological characters of the stylodia, calyces and secondary growth (Köhler 2003). The affinities of the family with Caryophyllales were confirmed by subsequent molecular phylogenetic studies (e.g. Cuénoud & al. 2002; Brockington 2009, 2011; Soltis & al. 2011), which showed that Simmondsiaceae are closer to Rhabdodendraceae and/or to the remainder of Caryophyllid clade. Further information under Rhabdodendraceae.