Hydnellum compactum is a tooth fungus in the family Bankeraceae. It is found in Europe, where it grows in deciduous forest, typically under beech. Fruit bodies of the fungus grow singly or in groups. They are top-shaped, with convex or flattened upper surfaces up to 10 cm (4 in) in diameter. The surface texture is initially felt-like before becoming pitted and rough in age. The stipe, roughly the same color as the cap, is solid and measures 2–4 cm (0.8–1.6 in) long by 1–3 cm (0.4–1.2 in) thick. On the fertile cap underside (the hymenium) are white to purple-brown, curved spines up to 5 mm long. The color is whitish at first but gradually turns dark brown to blackish. Its spores measure 5.5–6 by 3.5–4.5 µm, and feature tubercles that sometimes have a sunken tip. It is considered endangered in Switzerland.
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