Haha we've all been there, I'm gonna guess which one you're missing and give you this hint! Near the comets, they'll give you a lift to your prize, but skewer your plans if you're under them.
Hey Paul! Sorry, sloths need a lot of sleep, even the mega ones and I was passed out.
Try the spiked platforms before the comets on your next go ;)
Haha ok you've tried long enough, the skull you're missing (I think) is on the spiked platforms before the comets, ride it up to its top then jump!