Toothed Cup

Toothed Cup (Tarzetta cupularis) is a modest, easily overlooked ascomycete of bare and disturbed ground. It belongs to the Pyronemataceae, a large family of soil-inhabiting cup fungi, and to a genus characterised by pale, drab, thin-fleshed cups with distinctly notched margins.

Unlike the brightly coloured cups that attract attention, Tarzetta cupularis relies on shape for recognition: a deep, almost hemispherical bowl, narrowed to a short stem-like base, with a rim divided into a ring of small pointed teeth. The colours are subdued — whitish, cream, greyish-buff or pale ochre — so the fungus blends into the soil it sits on.

It is common in the right habitat but frequently passes unrecorded because of its size and colour.

Fruiting body

Cups 0.5–2 cm across, deep and cup- or urn-shaped, remaining fairly deep rather than flattening out. The base narrows into a short, stout, stem-like extension that is usually partly buried.

Margin

The defining feature: the rim is crenulate to distinctly dentate, cut into a ring of small, roughly even, pointed or blunt teeth that persist as the cup expands.

Surfaces

The inner surface is smooth and pale grey-buff to cream. The outer surface is whitish and finely mealy or minutely scurfy, sometimes slightly granular near the base.

Flesh and spore print

The flesh is thin, whitish and brittle, without colour change. Spores are smooth and elliptical, giving a whitish print.

It fruits on damp, often compacted bare soil: woodland paths, track edges, banks, ditch sides, mossy clearings and disturbed ground in gardens. It shows a clear preference for calcareous and clay soils, and is often found on the same paths year after year.

The season is long, from late spring through autumn wherever the ground stays moist. The species is widespread across Europe and is reported from North America and other temperate regions.

Tarzetta cupularis is a soil saprophyte, decomposing fine organic matter, buried plant fragments and humus in mineral soil. It is a characteristic member of the community of small cup fungi that colonise recently disturbed or compacted ground, alongside genera such as Peziza, Humaria and Geopora.

Fruiting follows rain, with cups appearing singly or in small clustered groups, often partly sunk in the substrate so that only the toothed rim shows at first.

Tarzetta catinus is the closest relative and is larger and broader, expanding into a shallower saucer with a less strongly toothed, more wavy margin. Humaria hemisphaerica is similar in size and shape but has a bright white inner surface contrasting with a dense coat of stiff brown hairs on the outside, and the margin is hairy rather than toothed. Geopora species begin buried and split open irregularly at the top in a star-like fashion, and their outer surface is brown and hairy. Small Peziza species are usually thinner-fleshed, browner and lack an evenly toothed rim.

Depth of cup, dull pale colouring and the regular ring of marginal teeth together identify this species in the field.