No, that’s what I meant by not an axle.
But, come to think of it, we can swing our arms round and round, more than 360°.
How about this insect with a pair toothed gears? Not an axle, but still amazing!
“The juvenile Issus - a plant-hopping insect found in gardens across Europe - has hind-leg joints with curved cog-like strips of opposing ‘teeth’ that intermesh, rotating like mechanical gears to synchronise the animal’s legs when it launches into a jump.”
right, even trains don’t need diffs, the conic-slice wheels take care of turns fine without.
that’s reasonable.
bonus fun fact - the etymology is connected - “axle” comes from older words for “shoulder”, or “armpit”, which survives in some regional Englishes as “oxter” - the connection is apparently that you’d carry a person by putting their arms up and linking at the shoulders, much like an axle is how wheels carry a cart.
https://www.etymonline.com/word/axle