Hymenoxys argentea (A. Gray) K. F. Parker var. thoreauensis N. D. Atwood, S. L. Welsh & A. Clifford was applied by Atwood and Welsh (2007) to discoid plants growing north of Thoreau, New Mexico, “… with other mound-forming plants on a remaining lens of the windswept Todilto Limestone with limy sands and limestone gravel on the point of the Mesa above the limestone cliffs.”

Atwood and Welsh (2007) stated, “We maintain use of Hymenoxys over the segregate Tetraneuris out of personal choice and belief in a stable nomenclature.” It is their prerogative to use Hymenoxys rather than Tetraneuris. How this helps maintain a stable nomenclature is unclear to us, given that the most recent and most comprehensive treatments of the group to which these plants are referable recognize Tetraneuris as a genus separate from Hymenoxys (Bierner and Turner, 2003; Panero, 2007).

Some relatively recent workers have recognized Tetraneuris as an infrageneric grouping within Hymenoxys (e.g., Barkley, 1986; Cronquist, 1994; Karis and Ryding, 1994; Welsh, 1987). Other recent workers have recognized Tetraneuris at the generic level (e.g., Baldwin and Wessa, 2000; Baldwin et al., 2002; Bierner, 1994; Bierner and Jansen, 1998; Bierner and Turner, 2003; Spring et al., 1994). Morphological and chemical differences between taxa referable to Tetraneuris and taxa referable to Hymenoxys have been discussed at length (e.g., Bierner, 1978, 2001; Bierner et al., 1992; Díaz et al., 1992; Ferracini et al., 1994).

Atwood and Welsh (2007) cited Bierner and Turner's (2006) treatment for Flora of North America North of Mexico, but they did not cite Bierner and Turner's (2003) taxonomic treatment, which presented multiple lines of evidence for the recognition of Tetraneuris, nor did they cite Panero (2007) or Baldwin et al. (2002). The latter not only supports recognition of Tetraneuris, it corroborates Bierner (1994) and Bierner and Jansen (1998), supporting recognition of Tetraneuris.

Taxonomy