Description: Thallus crustose, episubstratic, yellow, areolate or formed of aggregated, corticate squamules which are (in average) 190 μm thick and 0.7 mm wide, flat, smooth, with marginal soralia which in old thalli may cover the whole surface. Soredia (22-)26-46(-61) μm in diam., sometimes gathered into consoredia. Apothecia zeorine, 0.3-0.6 mm across, with a flat to convex disc, and a sorediate thalline margin which, in young apothecia, is hidden below the proper margin, becoming more evident in old apothecia. Epithecium orange, K+ red; hymenium colourless, 60-80 μm thick; paraphyses tips widened at apex to 3-6 μm. Asci 8-spored, clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, ellipsoid, in average 11 x 6 μm, the septum c. 4.5 μm thick. Photobiont chlorococcoid. Spot tests: thallus, soredia and apothecia K+ red, C-, KC-, P-. Chemistry: thallus and apothecia with parietin (major), fallacinal, emodin, teloschistin and parietinic acid (minor), corresponding with chemosyndrome A of Søchting (1997).
Note: a species of the F. citrina group with an areolate to subsquamulose, usually yellow to greenish-orange thallus and marginal soralia, apothecia not rare; mostly on artificial substrates like concrete or mortar in strongly manured places, e.g. in sites visited by dogs; certainly much more common and hidden behind records of F. citrina.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)