These mushrooms have a center that resembles a puffball, surrounded by rays that clasp and surround the spore sac in dry weather, then open in response to rain, as seen in these photos, and giving it its common name of barometer earthstar. Widespread in North America, often in sandy soil near conifers. Frequently found in large groups.
The spore sac is felty-rough, nearly round, 1-3 cm (3/8 - 1-1/4in.), whitish, then becoming gray to brown, with a small irregular opening at the top. The spore sac is covered by a grayish-brown skin that splits into six to twelve lobes, opening in wet weather into star-like rays 2.5-5 cm (1 - 2in.) long. These rays curl under to hold the spore sac aloft above the ground, then close in dry weather.
Astraeus hygrometricus is one of several species in the single genus making up the Astraeaceae family. The classification above that has been going through changes, and varies from source to source. There is another genus of earthstars - Geaster - that is placed in a different family and order.
These earthstars were photographed the day following a night of rain.
For a taxonomic tree and links to other fungi posted on Wild Florida Photo see the Fungi at Wild Florida Photo page.