Montanucci R. R., Kleszewski K. P., Taxonomic history, comparative morphology, and variation in Astrophytum myriostigma and its subspecies tulense (Cactaceae), Journal of the Botanical Research Institute of Texas, 2021, 15(2):327-341, doi: 10.17348/jbrit.v15.i2.1152
The authors compare morphology of Astrophytum myriostigma and plants treated as tulense. They analyse rib number, stem proportions and historical name treatments, among other features.