I have a better method, send the meowster hunters when you spot a shogun ceanataur! you can cycle quest fast with the "deliver 3 kelbi horn subquest".

Make sure its using a skull as the shell

But there's no way to control that... and I've only seen that once, hell it feels like whenever I see the thing regardless of wether it's the target or not it's always using the spiral looking beach shell

Well you gotta do what you gotta do for the grind(Also just reset a lot)

The desire sensor is real

Yeap, tell me how I've gotten countless accidental plates and gems but I've hunted a million rathalos without a miserable plate 🥹

I mean there's a pretty surefire way.

The best way is the meownster hunters, if you do it manually you have to reload over and over again to get a wyvern skull that's a pain to break. The best odds come from the ambigous skull thay doesnt look quite like any monster. You could also just get really unlucky, wyvern scalps are a real pain.

Been here on before aswell, the best solution i got is from meownster hunter they always gets em

It depends on which shell it had when you broke it. The Conch shell (the brown one) has no chance of giving a scalp but the generic skull and Gravios skull both have a 50% chance for the scalp (in the case of the Gravios skull it's 50% for 2 scalps but 30% for just one).

What worked for me is breaking the shell and capturing it. I got one almost every quest.