Hymenoxys (rubberweed or bitterweed) is a genus of plants in the sunflower family, native to North and South America. It was named by Alexandre Henri Gabriel de Cassini in 1828. Plants of this genus are toxic to sheep due to the presence of the sesquiterpene lactone hymenoxon. • Hymenoxys acaulis is now called Tetraneuris acaulis • Hymenoxys argentea now Tetraneuris argentea • Hymenoxys depressa now Tetraneuris torreyana • Hymenoxys glabra now Tetraneuris scaposa • Hymenoxys herbacea now Tetraneuris herbacea • Hymenoxys integrifolia now Helenium integrifolium • Hymenoxys ivesiana now Tetraneuris ivesiana • Hymenoxys lapidicola now Tetraneuris torreyana • Hymenoxys linearifolia now Tetraneuris linearifolia • Hymenoxys scaposa now Tetraneuris scaposa • Hymenoxys torreyana now Tetraneuris torreyana • Hymenoxys turneri now Tetraneuris turneri