Isocoma azteca

Herbage glabrous, sometimes sparsely stipitate-glandular, not resinous. Leaf blades narrowly oblong to narrowly oblanceolate, 20-50 mm, margins shallowly to deeply pinnatifid (lobes in 3-8 evenly arranged pairs, apically aristate). Involucres 7-8 × 5-7.5 mm. Phyllary apices green to greenish yellow, not aristate, sparsely to prominently gland-dotted, without resin pockets. Florets 18-25; corollas 5-6 mm. Cypsela ribs not forming apical hornlike extensions.

Flowering Jul-Sep. Slopes, river edges, sandy to clay soils, gypseous or saline, badlands in pinyon-juniper woodlands, commonly with Atriplex; 1500-1800 m; Ariz., N.Mex.

Isocoma azteca is similar to I. rusbyi in most features and perhaps most closely related to it; the pinnate leaves of I. azteca are distinctive. The two taxa are essentially contiguous in range along the New Mexico-Arizona border and their interaction in natural populations needs to be studied.