Parvocaulis parvulus

Thallus solitary or in groups, small 2–2.5(–5) mm high, parasol-shaped, bright green, slightly calcified, ~5 mm high. Apical disc (cap), flat, 1.8–3 mm diam., composed of 12–20 rays. The rays obovoid-clavate with rounded or nearly truncated apices slightly cemented together laterally through calcification. Corona superior shortly cylindrical (100–110 mm high), round in the surface view with four rarely three, five sterile hairs or hair scars; corona inferior lacking. Hairs light green to dark green (in dependence on habitat), to 2.1 mm long, branching dichotomous (to 4 times). Stipe with transverse corrugations in the upper portion, 2.0–2.5 mm high, (rarely to 5 mm), to 300 mm diam. at base and to 500 mm diam. above. Gametangia are mature rays filled with spherical cysts, (60–)75–100 mm diam. Attachment by inconspicuous, small, finger-like holdfast. Growing on hard substrates, on damaged and dead corals at shallow sites.

In tropics and subtropics of Atlantic, Indian and Pacific Oceans.