What unusual shape does wombat poop take?

Wombats produce droppings shaped roughly like cubes, an oddity caused by sections of their intestines that stretch and firm up the waste unevenly, flattening its sides as it passes through. This cube shape is thought to help the pellets stay stacked in place on logs or rocks, where wombats use them to mark territory, rather than rolling away like round droppings would.

A perfect sphere or a flat disk would both roll or slide off an angled surface fairly easily, which would defeat the apparent purpose of using droppings as a stable, visible territory marker — the cube's flat sides are specifically what keep it from moving.

Researchers who studied this closely found the shaping happens due to varying stretchiness in different parts of the wombat's very long intestine, not from any special muscle that presses the waste into a mold.