From Rio grande de sol in Brazil, Gymnocalycium denudatum is a normally solitary, globular, glossy green cactus to 6 inches across and 4 inches tall. It turns a lovely purplish brown in my greenhouse over winter. It's common name is very appropriate. Taking on whimsical random twists and turns, the spines almost look like little fuzzy spiders crawling across it. Mine is so shiny it almost looks like it's made of wax. It gets white to pink flowers almost 3 inches across in spring and summer. I'll put up pics when that happens.

The same plant prior to winter

A closeup of the whimsical spination

First flower

A closer view