Geastrum pectinatum

Geastrum pectinatum is a species of fungus in the earthstar family. It is commonly known as the beaked earthstar or the beret earthstar, in reference to the shape of the spore sac and its prominent, protruding peristome.

Although young specimens are spherical, fruit body development involves the outer layer of tissue splitting open like a star into 7 to 10 pointed rays that eventually bend back to point downward, revealing a small spore sac, 1 to 2.5 cm (1⁄2 to 1 in) broad. The spore sac is supported by a small radially wrinkled stalk. There is a distinct conical opening (peristome) at the top of the spore sac that is up to 8 mm (3⁄8 in) long. The mass of spores and surrounding cells within the sac, the gleba, is dark-brown, and becomes powdery in mature specimens. The spores are spherical, measuring 4 to 6 micrometers in diameter, with warts on their surfaces. Like several other earthstars, crystals of calcium oxalate are present, thought to be involved in fruit body maturation.

G. pectinatum grows on the ground in open woods. Although uncommon, it has a cosmopolitan distribution and has been collected in Eurasia, the Americas, Australia, and Africa. It is inedible.