Pelecyphora aselliformis, commonly known as the "Hatchet Cactus", is one of the most iconic cacti, renowned for its uniquely shaped stem. The pectinate spines resemble woodlice or sowbugs (Oniscus asellus), which inspired the species name.

Mature stems are spherical to short-cylindrical. Juvenile plants, however, display a slender, pencil-thin or clavate stem, distinctly different in shape and proportion from the more compact mature structure.