Geastrum pectinatum

Geastrum pectinatum is an inedible species of mushroom belonging to the earthstar family of fungi. 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 – 1 to 2.5 cm (1⁄2 to 1 in) broad – spore sac. 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. 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. The mass of spores and surrounding cells within the sac, the gleba, is dark-brown, and becomes powdery in mature specimens. Spores are spherical, measuring 4 to 6 micrometers in diameter, with warts on their surfaces.

Although uncommon, G. pectinatum has a cosmopolitan distribution, and has been collected in various locations in Europe, North and South America, Asia, Australia and Africa, where it grows on the ground in open woods. Like several other earthstars, crystals of calcium oxalate are found on G. pectinatum, and are thought to be involved in fruit body maturation.