| Otopappus pringlei (Greenm.) S.F. Blake, 1915 |
| Otopappus robinsonii Klatt, 1894 |
| Otopappus robustus Hemsl., 1881 |
| Otopappus scaber S.F. Blake, 1924 |
| Otopappus serboana B.L. Turner, 2013 |
| Otopappus tequilanus (A. Gray) B.L. Rob., 1909 |
| Otopappus tequilanus var. acuminatus (S. Watson) B.L. Rob., 1909 |
| Otopappus tequilanus var. griseus McVaugh, 1972 |
| Otopappus trinervis S.F. Blake, 1915 |
| Otopappus verbesinoides Benth., 1873 |
| Otopappus xanthocarphus Brandegee, 1909 |
| Oxydon Less., 1830 |
| Oxydon bicolor Less., 1830 |
| Oxylobinae R.M. King & H. Rob., 1980 |
| Oxylobus (Moc. ex DC.) A. Gray, 1880 |
| Oxylobus adscendens (Sch. Bip. ex Hemsl.) B.L. Rob. & Greenm., 1905 |
| Oxylobus arbutifolius (Kunth) A. Gray, 1879 |
| Oxylobus coyulensis Redonda-Mart. & E. Martínez, 2019 |
| Oxylobus glandulifer (Sch. Bip. ex Hemsl.) A. Gray, 1879 |
| Oxylobus juarezensis Rzed. & Calderón, 2013 |