Human elytra flying off a cliff
I imagined a person who's scapulae is overly developed and extruding outside the shoulder girdle like an elitra or fixed plane wings.
They can be moved by shrugging the shoulders or rotated by raising the arms.
Being them basically just big scapulae that double as elytras they are controlled by the normal shoulder muscles.
So my question would be; how large do those elytra-scapulae need to be to allow a human to jump off a cliff and plane close to the surface of the water for at least a few minutes?
This is probably impossible, but your question leaves off necessary detail to know for sure. If the point is to be able to glide for "a few minutes" after jumping off something tall, then we need to know how tall. The taller the cliff, the more potential energy there is to power the flight.
You also say you want to "plane close to the surface of the water" for a few minutes. First, you didn't mention anything about water, so it's not clear how that fits in. However, if you expect to glide close over something flat, then you're not getting any power input from potential energy. You are gliding from momentum only, or perhaps a very slight decrease in altitude, which isn't going to last long. Even with ground effect, the drag would have to be impossibly low.
Your concept doesn't pass the basic physics test.
You will also find that bone is a very poor material for making wings from, especially the large low-speed wings you require.
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An average human masses 60Kg. The largest bird ever to fly, Argentavis, massed about that much.
So it seems reasonable that flying creatures the same weight as a human need to be reasonably close to Argentavis's size. Argentavis' wingspan was about 6m, and wing area over 8 square meters.
Assuming that your scapulae-wings are somehow as light and strong as stretched skin and feathers over an articulated bone frame, one would expect each scapulae-wing to be almost 3m long and average 1m wide, while not contributing much extra mass to the person at all.
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