Earthstars are puffballs(a type of mushroom) that have an outer skin that splits into starlike rays, leaving the spore case exposed. These rays sometimes curl back and under the spore case, forming 'legs' that support the rounded case. These fungi assume such contorted and unusual poses that one of the common names is Acrobatic Earthstar. The scientific name for that particular species is Geastrum fornicatum, for reasons I don't completely understand. One of the interesting things about Earthstars si that they are sometimes hygroscopic, the rays open in wet weather, yet close up in dry weather to protect the spore case. If you find one of these beauties, you can make it do it's dance by placing it in water ar home. The rays will open even if the mushroom is several years old.
Earthstars occur in a variety of habitats, but are particularly common in arid and semi-arid regions, like the Southwestern United States. They are very popular because of their odd shapes and hygroscopic properties, but are not edible, due to their tough and woody texture. They are often found growing near juniper trees. The Giant Hygroscopic Earthstar is particularly impressive, having huge rays with a cross hatch pattern on them. These fungi can reach a width of 7 inches when fully expanded, and are quite common year round in some areas of the Western United States.