Hydnellum is a genus of tooth fungi in the family Bankeraceae (order Thelephorales). Widely distributed in the Northern Hemisphere, the genus contains around 40 species. The fruitbodies of its members grow by slowly enveloping nearby bits of grass and vegetation. There is great variability in the form of Hydnellum fruitbodies, which are greatly influenced by environmental conditions such as rainfall and humidity, drying winds, and temperature. They are too tough and woody to eat comfortably. Several species have become the focus of increasing conservation concern following widespread declines in abundance. Hydnellum species produce pigments that have been used to dye textiles. Several chemical compounds—some with unique biological activity—have been isolated and identified from the genus. One of the better-known species is the unusual pinkish-white Hydnellum peckii, also known as "strawberries and cream" or as the "bleeding tooth fungus" due to the red droplets that appear on the pinkish or whitish fruitbodies. Another species, H. suaveolens, has a strong odor of anise or peppermint. Taxonomy Hydnellum was circumscribed by Finnish mycologist Petter Adolf Karsten in 1879 with what was then known as Hydnum suaveolens as the type species. Before then, fungi with spines (hydnoid fungi) had been grouped in Hydnum by Elias Fries in his 1821 work Systema mycologicum. Karsten defined Hydnellum as having fruitbodies with a corky or leathery, tough cap, and a centrally attached stipe. Synonyms of Hydnellum include Calodon (Karsten, 1881), and Phaeodon (Joseph Schröter, 1888). Hydnellum is classified in the family Bankeraceae, which was circumscribed by Marinus Anton Donk in 1961. The genus was not in Donk's original family concept, which included only Bankera and Phellodon, genera whose species produce hyaline (translucent), and ornamented spores. Donk left Hydnellum in the tribe Hydnelleae of the family Thelephoraceae, along with Sarcodon and Hydnodon. In 1981, however, Walter Jülich emended Donk's concept of the Bankeraceae, adding hydnoid genera that produced brown, lobed spores—Hydnellum and Sarcodon. The name originates from the Greek word ύδνο (=hydnum) meaning "spongy plant" or "fungus". The British Mycological Society, in their recommended list of common names for fungi in the United Kingdom, name Hydnellum fungi in the form "descriptor word" plus "tooth", such as "gold tooth" (H. auratile), "zoned tooth" (H. concrescens), and "velvet tooth" (H. spongiosipes). Phylogeny Phylogenetic studies have shown that, in its current circumscription, the genus Hydnellum is polyphyletic and only distantly related to the white-spored genera Bankera and Phellodon, currently grouped together