This is a mcrolichen that is quite characteristic, and recognizeable to non-specialists.
Morphology: Thallus corticolous, to 11 cm diam, grey-brown to brown, lobes broad, 0-5-1 0(-20) cm wide, often markedly coriaceous, closely adpressed, often + elongated, contiguous or + overlapping at the centre. Upper surface
minutely scabrid (lens), smooth or faintly reticulate-sulcate, sulcae dispersed, soredia and isidia absent. Margins rarely entire, with numerous folioles. Lower surface dark brown-black, areolate-scabrid and obscurely ridged, in part naked or markedly spongy pubescent to tomentose. Medulla white. Photobiont Nostoc.
Apothecia common, rounded to reniform, disc red-brown-black, margins entire or rarely with folioles, with a +/- raised thalline cuff, dorsal surfacerarely laminal, on short projections. Anatomy: Thallus 250-275 μm thick. Upper cortex 36-45 μm thick, pseudoparenchymatous, +/- uneven, 3—6 cells thick, colourless to pale straw, lumens
rounded, 4-7 μm diam. Lower cortex 40-45 μm thick, 3-4 cells thick; inner cells pale, lumens 8-11 x 4—6 μm; outer cells +/- red-brown, lumens rounded, 5-9 μm, extended into hairs c. 13 cells long; lower cells of hairs rounded with red-brown walls, 3-5 um diam, upper cells + elongate, pale, 3.5-4 x 3 μm. Cortex above apothecia thick, uneven, 50-60 μm, c. 10 cells thick, cells colourless or pale straw, lumens 4—7 μm. Photobiont layer c. 45 μm thick, Nostoc cells
violet-blue or cyanescent, 4—8 μm, closely compacted. Medulla 135-150 μm thick, compact, with interwoven hyphae c. 4-5 μm thick. Thecium 68-72 μm high; epithecium red-brown; paraphyses simple with apices +/- conglutinated with pigment; asci 45-48 x 14—17 μm. Spores pale to medium red-brown, ellipsoid, 3-septate, 18.5-22.7 x 6.8-7.3 μm. Conidia ellipsoid with rounded ends or rarely tapered at one end, 4.0—4.5 x 1.5-2.0 μm.

This is a large macrolichen species belonging to a taxonomically well-known genus. It only occurs on Madeira, and there only on trees in the native mountain forest, which is under threat from developments for tourism and change of microclimate as a result of global warming and developments further down on the island.

Criterion A: Not applicable.
Criterion B: Area of Occupancy <500 km2; Extent of Occupancy <100 Km2 B1a Number of locati
B1b= Forest in Madeira has been continously degraded during the last century (citation needed!!)
Criterion C: Not applicable
Criterion D: Number of mature individuals not known.
Vulnerable under criterion D2: number of locations less than 5.

Final assessment: Critically Endagered under criterion B1a,b.

Madeira

Only known from a small area around Ribeiro Frio on Madeira. Known population small, Area of Occupancy very small, probably less than a few square meters.
Exact Area of Occupancy unknown, but certainly <500 km2; Extent of Occurrance also certainly <100 km2

On various trees (not only native ones) in native mountain forest around 850 m. This forest is known as laurisilva, a threatened habitat that is endemic to Macaronesia which has suffered severe losses in the past century.

Direct: Destruction of forest for tourist accomodation and road developments, and forest fire.
Indirect: Change of microclimate by global warming and by developments at lower altitudes, which result in an overall warmer and dryer madeira, making the forest noticeably dryer in recent decades, shown e.g. by the more frequent fires.
Also: this species should not be collected any further by lichenologists or naturalists. It should feature on a leaflet with protected plants.
A summary of threats to Madeira laurisilva forests can be found from the WWF: http://www.worldwildlife.org/ecoregions/pa0425

Protect not only the last remnants of native forest but also large streches of planted forest around these, to buffer changes in microclimate.

James, P.W. and White, F.J. 1987 Studies on the genus Nephroma I. The European and Macaronesian species. Lichenologist 19: 215-268.

Sérusiaux, E. 1989 Liste Rouge des macrolichen dans la Communauté Europeenne. Département de Botanique, Liège.