Parodia ottonis

The plant at first grows individually and later forms groups. The light to dark green or blue-green spherical shoots are often tapered towards the base. They reach diameters of 3 to 15 centimeters. The six to 16 distinct ribs are rounded or sharp-edged. There are usually only a few areoles on each rib. The bristle-like thorns that spring from them are straight, curved or twisted. The one to four central spines are brownish, reddish brown or yellowish and have a length of 0.8 to 4 centimeters. The four to 15 spines are whitish to yellowish or brownish and 0.5 to 3 centimeters long. The usually yellow flowers, rarely orange-red or red, reach lengths of 5 to 6 centimeters and would appear in late summer. Its flower tube is covered with brownish wool and bristles. The scars are dark red. The thick-walled egg-shaped to short cylindrical fruits tear open. They have diameters from 0.9 to 1.3 centimeters. The fruits contain, often very numerous, bell-shaped, glossy black seeds, which are strongly humped.

Parodia ottonis is common in southern Brazil, southern Paraguay, Uruguay, and northeastern Argentina.