Why has no animal species ever evolved wheels?

The problem with your CD example is that it not only lacks a fixed axle, but there’s no evident way to make the disc rotate.

Link to thread.

Not so hard to imagine ones that could exist. The bottom line of the column though is a good one. Truth be told wheels are not so practical for the the variety of environments that most complex animals need to be able to traverse. You need to travel in trees? Wheels suck. Go up steep inclines? Better to have at least two feet. Get over logs and boulders in your path? Wheels not so good. Go up nature’s natural staircases? On wheels?

The natural world is not best traversed with wheels. No selective pressure.

Humans evolved wheels, they are secreted from our digital organs.

Here is a better diagram of the rotating flagellum structure:

https://en.wikipedia.org/wiki/File:Flagellum_base_diagram_en.svg

Why not have pairs of wheels, each pair would have one which contacts the ground and rotates, while the other lifts up off the ground and goes backwards, they take turns supplying locomotion and the axles (made of muscle) twist a turn or two and then reset? I could imagine that one evolving on a fairly flat sort of terrain.

Sounds kind of like a foot…