Setchellanthaceae (Capparales), a new family for a relictual, glucosinolate‐producing endemic of the Mexican deserts

Summary Iltis, H. H.: Setchellanthaceae (Capparales), a new family for a relictual, glucosinolate‐producing endemic of the Mexican deserts. – Taxon 48: 257‐275. 1999. – ISSN 0040‐0262. Setchellanthus caeruleus Brandegee is a rare microphyllous shrub, densely pubescent with T‐shaped Malpighian hairs, with many stamens, 5‐7 free blue to lilac petals, an elongate, 3‐carpellate, deeply trisulcate ovary with axile placentation and proto‐parietal vasculature, and a straight embryo essentially lacking endosperm. It is known only from two widely disjunct areas in the Chihuahuan and Tehuacán deserts of northern and south‐central Mexico. The genus was named for phycologist W. A. Setchell (1864‐1963; a biographical note is included). Its taxonomy, morphology, and geography are outlined, and the results of four associated papers on flower and seed anatomy, vegetative anatomy, pollen structure, and nucleotide sequence of the rbc L gene are discussed. The species is so highly distinct in its relatively primitive morphology and chemistry that it is here placed into its own, newly established monotypic family near the Caricaceae and Moringaceae and basal to the core group of glucosinolate (mustard oil) producing families (but less basal than, e.g., Bretschneideraceae, Akaniaceae, and Tropaeolaceae). The new evidence supports Dahlgren's reclassification of an expanded order Capparales.