Known for many years from a single Michigan collection from Union Lake, Oakland Co. (D. J. Ameel in 1928, MICH). Recently (2021) re-disovered in Michigan by A. Klain in Kalamazoo Co. 

Occasional specimens of C. erythrorhizos have the tips of the lower scales very slightly spreading and might run here in the key. They are readily distinguished from C. acuminatus by their shorter anthers, ribbed scales, and abundant pinnate inflorescences.