These western North American natives are sparse, weedy-looking annuals with long branching erect stems and little foliage, and many bear bird's-beak–shaped flowers.

[1] Bentham also used Nuttall's specific epithet, Cordylanthus filifolius instead of C. rigidus, it took until 1911 before Willis Linn Jepson noticed this was a nomen illegitimum and corrected the name.

[2][3][4] In three different 1891 publications three different botanical taxonomists, the American Edward Lee Greene, the Austrian Richard Wettstein and the German Otto Kuntze, had all pointed out that Bentham's name had priority.

What Ferris neglected to mention in her monograph was that at the 1905 Vienna congress, the matter of the junior synonym Cordylanthus had been discussed, and it had been decided to conserve Nuttall's name.

[2][3][7][8] In Harvard University James Francis Macbride was rather critical of Ferris's work, moved the species back to Cordylanthus the following year, furthermore sinking a number of her newly described taxa into synonymy.

[10] The next authors to revise the genus were David C. Tank, John Mark Egger and Richard G. Olmstead in 2009, using molecular phylogenetic work to tease out the relationships.