Geastrum fornicatum, common name known as the acrobatic earthstar or the arched earthstar, is an inedible species of mushroom in the family Geastraceae. Like other earthstar mushrooms, the thick outer skin splits open at maturity to expose the spore sac to the elements; the specific epithet fornicatum (Latin for 'arched' or 'vaulted') refers to the arched shape of the rays which extend downwards to rest on the mycelial sac and elevate the spore sac.