Hecastocleis A. Gray, is a monotypic genus that has always been placed in tribe Mutisieae.  However, it possesses some unusual morphological features: heads are single flowered and are re-aggregated on a secondary receptacle and each group of 1-5 heads is subtended by a relatively large spiny whitish or greenish bract.  It is isolated in the phylogeny of the family and it is now placed in a subfamily (Hecastocleoideae) and a tribe (Hecastocleideae) of its own.  The location of Hecastocleis on the supertree, just above the basal grade from southern South America and before the large radiations in Africa and Asia, confounds the biogeography of this section of the tree.  It grows in harsh environmental conditions high in the mountains around Death Valley and Las Vegas (southern Nevada and adjacent California).