Crocodia aurata
Thallus 2–6 (–10) cm diam., forming rosettes or irregularly spreading; lobes 3–12 mm broad, rounded or indented at the apices, often discrete at margins and overlapping centrally; upper surface bright green when wet, pale grey when dry, smooth, undulate, often scabrid-areolate in parts, ± pubescent at the margins, bearing conspicuous coarsely granular bright yellow ± linear lip-like marginal soralia which occasionally also spread on to the upper surface; medulla yellow; lower surface pale pink-brown, darker towards the centre, thickly tomentose to the margins, ± wrinkled-uneven with numerous yellow pseudocyphellae, 0.1–0.6 mm diam.; photobiont green. Medulla and soralia C–, K–, KC–, Pd–, UV+ dull to bright orange or salmon-pink (pulvinic acid, pulvinic dilactone and calycin).
Information abstracted from Revisions of British and Irish Lichens vol. 20 (2021).
Assessed as Critically Endangered (C2 IR) by Woods & Coppins (2012).
Characterized by the bright yellow, predominantly marginal linear soralia, yellow medulla and green photobiont. Pseudocyphellaria citrina (P. crocata auct. br.) commonly has both laminal and marginal soralia, a white to only pale yellow medulla, a blue-green photobiont and Pd+ orange medulla.
Channel Islands (Sark), Isles of Scilly, S.W. Ireland (S. Kerry, Blasket Island). Formerly in S. and S.W. England but now extinct in those areas.
On trees, rocks and Calluna stems, and rabbit-grazed coastal turf.