>>11764434Pretty sure there are sails in nature. Various forms of seed dispersion come to mind. The sycamore seed is sort of a propellor too.
Sails are just vertical wings anyway. Even, counter intuitive to what I believed, square sails. They're all essentially aerofoils and work the same way. They're rare in nature because perhaps because the sails are only really effective in conditions where you can hold a straight line for long periods. Like on the water or over flat desert planes. No animals really float solely on the surface of water nor travel the desert without legs or wings. You can occasionally see sea birds use their wings as sales over short distances seemingly just for a laugh but they would quickly fall victim to predators staying on the surface too long without the ability to fly off.
The Issus Coleptratus bug has toothed gears on it's joints so perhaps a propeller developing in nature isn't utterly impossible but I don't think it would be a desirable trait for an animal. Propellers get tangled in shit and easily damaged. They can be very annoying. A flesh propellor blade would be even more fragile and would quickly render the creature lame in the water to drown or get munched. Don't forget also that the propeller is a very recent invention for humans. It hasn't even propelled our ships for 200 years yet and developed out of steam engine and the wheel. Which also don't yet occur in nature.
t. Tallship Sailor.
