Parodia ottonis, also known as Indian head cactus, is a cactus found in Argentina, Brazil, Paraguay and Uruguay. There are two recognized subspecies.[1] The epithet ottonis honors the German botanist Christoph Friedrich Otto.
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.[2]
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.[3]
Parodia ottonis is common in southern Brazil, southern Paraguay, Uruguay, and northeastern Argentina.[4]
The first description as Cactus ottonis by Johann Georg Christian Lehmann was published in 1827. Nigel Paul Taylor presented the type 1987 in the genus Parodia . Other nomenclatural synonyms are Echinocactus ottonis (Lehm.) Link & Otto (1830), Malacocarpus ottonis (Lehm.) Britton & Rose (1922), Notocactus ottonis (Lehm.) A.Berger (1929) and Peronocactus ottonis (Lehm.)[5]
The following subspecies are distinguished: