Sclerocarpus

Sclerocarpus is a genus of flowering plants in the sunflower tribe within the daisy family. Bonebract is a common name for plants in this genus. It includes annuals and procumbent perennials which occur primarily in Mexico and Central America, with one species extending as far north as the state of Texas in the USA and another species widely distributed across the West Indies, South America, Africa, and Asia. The genus is distinguished morphologically by the pales, which are modified to completely and tightly enclose the mature cypsela (achene) and often have a tuberculate surface. Some species of Aldama have a somewhat similar modification of the pales but in those the pale surface is irregularly wrinkled and pitted rather than tuberculate. Sclerocarpus is a member of the sunflower subtribe, Helianthinae, and is placed by molecular data as a relatively basal member of the group.