The "Pompom Mushroom" or "Lion's Mane" (Hericium erinaceus) shown at the right explains by itself where the tooth fungi get their name. The long, slender, downward-pointing "teeth" bear spore-producing basidia, as diagrammed on our Kinds of Fungi page. It's basically the same setup as with the gilled mushrooms, just that instead of gills the tooth fungi produce their spores on teeth. The picture was made in northeastern Mississippi. The fungus grows from a wound in a hardwood tree.
Tooth fungi are especially worth getting to know because many of them are delicious! In fact, the one Pompom Mushroom in the picture often is cultivated to be eaten.
In recent years DNA analysis has showed that many species traditionally regarded as "tooth fungi" aren't necessarily closely related. Tooth-like spore-bearing surfaces (the hymenophore) have evolved independently in several fungus orders and a highly disputed number of families, among which the Thelephoraceae and the Bankeraceae are prominent.